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1.Subclavian and axillary arteries and veins. Brachial, ulnar and radial arteries, topography and branches on arm, forearm and hand

2. Superficial and deep veins, lymphatics of upper extremity.

3. Brachial plexus, composition, topography

Lesson # 29

Theme 1. Subclavian and axillary arteries and veins

Left Subclavian artery starts from aortic arch and right one  - from the brachiocephalic trunk. It leaves thoracic cavity through the superior aperture, rounds a pleura cupola and gets into interscalenus space. Then artery lies under clavicle into same name sulcus of first rib and runs into axillary cavity, where has a name axillary artery. Subclavian artery conventionally subdivides into three portions: before interscalenus space, in interscalenus space and after interscalenus space. Before interscalenus space subclavian artery gives off the following branches:

Vertebral artery is a largest branch of subclavian artery, passes in foramens of transversal processes of cervical vertebrae, transfixes a atlanto-occipital membrane and dura mater encephali and through occipital foramen magnum gets into skull cavity. Behind pons this right and left artery flows together and forms basillar artery. Vertebral artery gives off anterior spinal artery and posterior spinal artery, and posterior inferior cerebellar artery. From basillar artery start: anterior inferior cerebellar artery, labyrinthic artery, pontini arteries and artery mesencephalic. Vertebral artery together with anterior spinal arteries forms around medulla oblongata circle of Zakharchenka.

Basillar artery on level of anterior margin pons ramifies on two posterior cerebral arteries, which supply occipital lobes of cerebrum. Posterior cerebral arteries connect by posterior communicating artery with internal carotid artery.  

 

 

 

 

 

Superficial dissection of the right side of the neck, showing the carotid and subclavian arteries.

 

 

Internal thoracic artery begins from inferior surface of subclavian artery and passes along І-VII cartilages of ribs near sternum, where disintegrates on two terminal branches are musculо-phrenic artery and superior epigastric artery. Internal thoracic artery gives off rami for thymus, bronchі, pericardium and sternum. Also from this artery moves away rami mammarii, tracheal rami, anterior intercostal branches, which supply intercostal muscles. Superior epigastric artery gets into sheath of rectus abdominal muscle, supplies this muscle and anastomoses with inferior epigastric artery on navel level.

Thyro-cervical trunk is has length 1-2 cm and subdivides into four branches: inferior thyroid artery, (supplies thyroid gland, cervical esophagus department, cervical trachea portion and inferior laryngeal artery reaches mucous membrane of the larynx), ascending cervical artery (to neck muscles), superficial cervical artery (to trapezius, rhomboid and other neck muscles) and suprascapular artery (for supraspinatus and infraspinatus muscles).

In interscalenus space subclavian artery gives off costo-cervical trunk, which ramifies into deep cervical artery, which supplies semispinalis capitis and cervicis muscles and suprema intercostal artery, which ramifies into I and ІІ intercostal spaces, supplying intercostal muscles.

After interscalenus space space subclavian artery gives off

transverse colli artery, which continues into dorsal scapulae artery. They supply rhomboid, levator scapulae and shoulder girdle muscles.

The artery which supplies the upper extremity continues as a single trunk from its commencement down to the elbow; but different portions of it have received different names, according to the regions through which they pass. That part of the vessel which extends from its origin to the outer border of the first rib is termed the subclavian; beyond this point to the lower border of the axilla it is named the axillary; and from the lower margin of the axillary space to the bend of the elbow it is termed brachial; here the trunk ends by dividing into two branches the radial and ulnar.

The internal mammary artery and its branches.

 

 

The Subclavian Artery (A. Subclavia)

 

—On the right side the subclavian artery arises from the innominate artery behind the right sternoclavicular articulation; on the left side it springs from the arch of the aorta. The two vessels, therefore, in the first part of their course, differ in length, direction, and relation with neighboring structures.

  In order to facilitate the description, each subclavian artery is divided into three parts. The first portion extends from the origin of the vessel to the medial border of the Scalenus anterior; the second lies behind this muscle; and the third extends from the lateral margin of the muscle to the outer border of the first rib, where it becomes the axillary artery. The first portions of the two vessels require separate descriptions; the second and third parts of the two arteries are practically alike.

 

First Part of the Right Subclavian Artery .—The first part of the right subclavian artery arises from the innominate artery, behind the upper part of the right sternoclavicular articulation, and passes upward and lateralward to the medial margin of the Scalenus anterior. It ascends a little above the clavicle, the extent to which it does so varying in different cases.

 

Relations.—It is covered, in front, by the integument, superficial fascia, Platysma, deep fascia, the clavicular origin of the Sternocleidomastoideus, the Sternohyoideus, and Sternothyreoideus, and another layer of the deep fascia. It is crossed by the internal jugular and vertebral veins, by the vagus nerve and the cardiac branches of the vagus and sympathetic, and by the subclavian loop of the sympathetic trunk which forms a ring around the vessel. The anterior jugular vein is directed lateralward in front of the artery, but is separated from it by the Sternohyoideus and Sternothyreoideus. Below and behind the artery is the pleura, which separates it from the apex of the lung; behind is the sympathetic trunk, the Longus collie and the first thoracic vertebra. The right recurrent nerve winds around the lower and back part of the vessel.

 

First Part of the Left Subclavian Artery—The first part of the left subclavian artery arises from the arch of the aorta, behind the left common carotid, and at the level of the fourth thoracic vertebra; it ascends in the superior mediastinal cavity to the root of the neck and then arches lateralward to the medial border of the Scalenus anterior.

 

Relations.—It is in relation, in front, with the vagus, cardiac, and phrenic nerves, which lie parallel with it, the left common carotid artery, left internal jugular and vertebral veins, and the commencement of the left innominate vein, and is covered by the Sternothyreoideus, Sternohyoideus, and Sternocleidomastoideus; behind, it is in relation with the esophagus, thoracic duct, left recurrent nerve, inferior cervical ganglion of the sympathetic trunk, and Longus colli; higher up, however, the esophagus and thoracic duct lie to its right side; the latter ultimately arching over the vessel to join the angle of union between the subclavian and internal jugular veins. Medial to it are the esophagus, trachea, thoracic duct, and left recurrent nerve; lateral to it, the left pleura and lung.

 

Second and Third Parts of the Subclavian Artery

  When a ligature is applied to the first part of the subclavian artery, the collateral circulation is carried on by: (1) the anastomosis between the superior and inferior thyroids; (2) the anastomosis of the two vertebrals; (3) the anastomosis of the internal mammary with the inferior epigastric and the aortic intercostals; (4) the costocervical anastomosing with the aortic intercostals; (5) the profunda cervicis anastomosing with the descending branch of the occipital; (6) the scapular branches of the thyrocervical trunk anastomosing with the branches of the axillary, and (7) the thoracic branches of the axillary anastomosing with the aortic intercostals.

 

Branches.—The branches of the subclavian artery are:

Vertebral.

Internal mammary.

Thyrocervical.

Costocervical.

  On the left side all four branches generally arise from the first portion of the vessel; but on the right side

The scapular and circumflex arteries.

  The Transverse Cervical Artery (a. transversa colli; transversalis colli artery) lies at a higher level than the transverse scapular; it passes transversely above the inferior belly of the Omohyoideus to the anterior margin of the Trapezius, beneath which it divides into an ascending and a descending branch. It crosses in front of the phrenic nerve and the Scaleni, and in front of or between the divisions of the brachial plexus, and is covered by the Platysma and Sternocleidomastoideus, and crossed by the Omohyoideus and Trapezius.

  The ascending branch (ramus ascendens; superficial cervical artery) ascends beneath the anterior margin of the Trapezius, distributing branches to it, and to the neighboring muscles and lymph nodes in the neck, and anastomosing with the superficial branch of the descending ramus of the occipital artery.

  The descending branch (ramus descendens; posterior scapular artery) passes beneath the Levator scapulæ to the medial angle of the scapula, and then descends under the Rhomboidei along the vertebral border of that bone as far as the inferior angle. It supplies the Rhomboidei, Latissimus dorsi and Trapezius, and anastomoses with the transverse scapular and subscapular arteries, and with the posterior branches of some of the intercostal arteries.

 

Peculiarities.—The ascending branch of the transverse cervical frequently arises directly from the thyrocervical trunk; and the descending branch from the third, more rarely from the second, part of the subclavian.

 

  3. The internal mammary artery (a. mammaria interna) arises from the under surface of the first portion of the subclavian, opposite the thyrocervical trunk. It descends behind the cartilages of the upper six ribs at a distance of about 1.25 cm. from the margin of the sternum, and at the level of the sixth intercostal space divides into the musculophrenic and superior epigastric arteries.

 

Relations.—It is directed at first downward, forward, and medialward behind the sternal end of the clavicle, the subclavian and internal jugular veins, and the first costal cartilage, and passes forward close to the lateral side of the innominate vein. As it enters the thorax the phrenic nerve crosses from its lateral to its medial side. Below the first costal cartilage it descends almost vertically to its point of bifurcation. It is covered in front by the cartilages of the upper six ribs and the intervening Intercostales interni and anterior intercostal membranes, and is crossed by the terminal portions of the upper six intercostal nerves. It rests on the pleura, as far as the third costal cartilage; below this level, upon the Transversus thoracis. It is accompanied by a pair of veins; these unite above to form a single vessel, which runs medial to the artery and ends in the corresponding innominate vein.

 

Branches.—The branches of the internal mammary are:

Pericardiacophrenic.

Intercostal.

Anterior Mediastinal.

Perforating.

Pericardial.

Musculophrenic.

Sternal.

Superior Epigastric.

  The Pericardiacophrenic Artery (a. pericardiacophrenica; a. comes nervi phrenici) is a long slender branch, which accompanies the phrenic nerve, between the pleura and pericardium, to the diaphragm, to which it is distributed; it anastomoses with the musculophrenic and inferior phrenic arteries.

  The Anterior Mediastinal Arteries (aa. mediastinales anteriores; mediastinal arteries) are small vessels, distributed to the areolar tissue and lymph nodes in the anterior mediastinal cavity, and to the remains of the thymus.

  The Pericardial Branches supply the upper part of the anterior surface of the pericardium; the lower part receives branches from the musculophrenic artery.

  The Sternal Branches (rami sternales) are distributed to the Transversus thoracis, and to the posterior surface of the sternum.

  The anterior mediastinal, pericardial, and sternal branches, together with some twigs from the pericardiacophrenic, anastomose with branches from the intercostal and bronchial arteries, and form a subpleural mediastinal plexus.

  The Intercoastal Branches (rami intercostales; anterior intercostal arteries) supply the upper five or six intercostal spaces. Two in number in each space, these small vessels pass lateralward, one lying near the lower margin of the rib above, and the other near the upper margin of the rib below, and anastomose with the intercostal arteries from the aorta. They are at first situated between the pleura and the Intercostales interni, and then between the Intercostales interni and externi. They supply the Intercostales and, by branches which perforate the Intercostales externi, the Pectorales and the mamma.

  The Perforating Branches (rami perforantes) correspond to the five or six intercostal spaces. They pass forward through the intercostal spaces, and, curving lateralward, supply the Pectoralis major and the integument. Those which correspond to the second, third, and fourth spaces give branches to the mamma, and during lactation are of large size.

  The Musculophrenic Artery (a. musculophrenica) is directed obliquely downward and lateralward, behind the cartilages of the false ribs; it perforates the diaphragm at the eighth or ninth costal cartilage, and ends, considerably reduced in size, opposite the last intercostal space. It gives off intercostal branches to the seventh, eighth, and ninth intercostal spaces; these diminish in size as the spaces decrease in length, and are distributed in a manner precisely similar to the intercostals from the internal mammary. The musculophrenic also gives branches to the lower part of the pericardium, and others which run backward to the diaphragm, and downward to the abdominal muscles.

  The Superior Epigastric Artery (a. epigastrica superior) continues in the original direction of the internal mammary; it descends through the interval between the costal and sternal attachments of the diaphragm, and enters the sheath of the Rectus abdominis, at first lying behind the muscle, and then perforating and supplying it, and anastomosing with the inferior epigastric artery from the external iliac. Branches perforate the anterior wall of the sheath of the Rectus, and supply the muscles of the abdomen and the integument, and a small branch passes in front of the xiphoid process and anastomoses with the artery of the opposite side. It also gives some twigs to the diaphragm, while from the artery of the right side small branches extend into the falciform ligament of the liver and anastomose with the hepatic artery.

  4. The costocervical trunk (truncus costocervicalis; superior intercostal artery) arises from the upper and back part of the subclavian artery, behind the Scalenus anterior on the right side, and medial to that muscle on the left side. Passing backward, it gives off the profunda cervicalis, and, continuing as the highest intercostal artery, descends behind the pleura in front of the necks of the first and second ribs, and anastomoses with the first aortic intercostal. As it crosses the neck of the first rib it lies medial to the anterior division of the first thoracic nerve, and lateral to the first thoracic ganglion of the sympathetic trunk.

  In the first intercostal space, it gives off a branch which is distributed in a manner similar to the distribution of the aortic intercostals. The branch for the second intercostal space usually joins with one from the highest aortic intercostal artery. This branch is not constant, but is more commonly found on the right side; when absent, its place is supplied by an intercostal branch from the aorta. Each intercostal gives off a posterior branch which goes to the posterior vertebral muscles, and sends a small spinal branch through the corresponding intervertebral foramen to the medulla spinalis and its membranes.

  The Profunda Cervicalis (a. cervicalis profunda; deep cervical branch) arises, in most cases, from the costocervical trunk, and is analogous to the posterior branch of an aortic intercostal artery: occasionally it is a separate branch from the subclavian artery. Passing backward, above the eighth cervical nerve and between the transverse process of the seventh cervical vertebra and the neck of the first rib, it runs up the back of the neck, between the Semispinales capitis and colli, as high as the axis vertebra, supplying these and adjacent muscles, and anastomosing with the deep division of the descending branch of the occipital, and with branches of the vertebral. It gives off a spinal twig which enters the canal through the intervertebral foramen between the seventh cervical and first thoracic vertebræ.

 Axillary artery is immediate continuation of subclavian artery. It passes in depth of armpit and covered by trunks of brachial plexus. According to topography of anterior wall of axillary cavity, axillarу artery subdivide into three portions: in clavipectoral triangle, pectoral triangle and subpectoral triangle.

In clavipectoral triangle axillar artery gives off:

·          superior thoracic artery, which ramifies in intercostal I-ІІ intercostal muscles;

·          thoracoacromial artery, which supplies acromial process, acromiо-clavicular joint, subclavius muscle, deltoid muscle, major and minor pectoral muscles.

In pectoral triangle from axillar artery moves away

- lateral thoracic artery, which supplies anterior serratus muscle and gives off the branches to mammary gland.

In subpectoral triangle axillar artery gives off:

·          anterior circumflex humeri artery - passes in front of surgical neck of humerus supplies shoulder joint and deltoid muscle;

·          posterior circumflex humeri artery - passes through quadrilaterum foramen and, anastomosing with previous artery, supplies shoulder joint and muscles, that are situated around it;

subscapular artery, which divides into thoracodorsal artery (supplies latissimus dorsi muscle and teres major muscle) and circumflex scapulae artery (passes through trilateral foramen and supplies muscles of back scapular surface).

The axilla is a pyramidal space, situated between the upper lateral part of the chest and the medial side of the arm.

 

Boundaries.—The apex, which is directed upward toward the root of the neck, corresponds to the interval between the outer border of the first rib, the superior border of the scapula, and the posterior surface of the clavicle, and through it the axillary vessels and nerves pass. The base, directed downward, is broad at the chest but narrow and pointed at the arm; it is formed by the integument and a thick layer of fascia, the axillary fascia, extending between the lower border of the Pectoralis major in front, and the lower border of the Latissimus dorsi behind. The anterior wall is formed by the Pectorales major and minor, the former covering the whole of this wall, the latter only its central part. The space between the upper border of the Pectoralis minor and the clavicle is occupied by the coracoclavicular fascia. The posterior wall, which extends somewhat lower than the anterior, is formed by the Subscapularis above, the Teres major and Latissimus dorsi below. On the medial side are the first four ribs with their corresponding Intercostales, and part of the Serratus anterior. On the lateral side, where the anterior and posterior walls converge, the space is narrow, and bounded by the humerus, the Coracobrachialis, and the Biceps brachii.

 

Contents.—It contains the axillary vessels, and the brachial plexus of nerves, with their branches, some branches of the intercostal nerves, and a large number of lymph nodes, together with a quantity of fat and loose areolar tissue. The axillary artery and vein, with the brachial plexus of nerves, extend obliquely along the lateral boundary of the axilla, from its apex to its base, and are placed much nearer to the anterior than to the posterior wall, the vein lying to the thoracic side of the artery and partially concealing it. At the forepart of the axilla, in contact with the Pectorales, are the thoracic branches of the axillary artery, and along the lower margin of the Pectoralis minor the lateral thoracic artery extends to the side of the chest. At the back part, in contact with the lower margin of the Subscapularis, are the subscapular vessels and nerves; winding around the lateral border of this muscle are the scapular circumflex vessels; and, close to the neck of the humerus, the posterior humeral circumflex vessels and the axillary nerve curve backward to the shoulder. Along the medial or thoracic side no vessel of any importance exists, the upper part of the space being crossed merely by a few small branches from the highest thoracic artery. There are some important nerves, however, in this situation, viz., the long thoracic nerve, descending on the surface of the Serratus anterior, to which it is distributed; and the intercostobrachial nerve, perforating the upper and anterior part of this wall, and passing across the axilla to the medial side of the arm.

  The position and arrangement of the lymph nodes are described on pages 699 and 700.

 

1. The Axillary Artery— (A. Axillaris)

The axillary artery, the continuation of the subclavian, commences at the outer border of the first rib, and ends at the lower border of the tendon of the Teres major, where it takes the name of brachial. Its direction varies with the position of the limb; thus the vessel is nearly straight when the arm is directed at right angles with the trunk, concave upward when the arm is elevated above this, and convex upward and lateralward when the arm lies by the side. At its origin the artery is very deeply situated, but near its termination is superficial, being covered only by the skin and fascia. To facilitate the description of the vessel it is divided into three portions; the first part lies above, the second behind, and the third below the Pectoralis minor.

 

Relations.—The first portion of the axillary artery is covered anteriorly by the clavicular portion of the Pectoralis major and the coracoclavicular fascia, and is crossed by the lateral anterior thoracic nerve, and the thoracoacromial and cephalic veins; posterior to it are the first intercostal space, the corresponding Intercostalis externus, the first and second digitations of the Serratus anterior, and the long thoracic and medial anterior thoracic nerves, and the medial cord of the brachial plexus; on its lateral side is the brachial plexus, from which it is separated by a little areolar tissue; on its medial, or thoracic side, is the axillary vein which overlaps the artery. It is enclosed, together with the axillary vein and the brachial plexus, in a fibrous sheath—the axillary sheath—continuous above with the deep cervical fascia.

  The second portion of the axillary artery is covered, anteriorly, by the Pectorales major and minor; posterior to it are the posterior cord of the brachial plexus, and some areolar tissue which intervenes between it and the Subscapularis; on the medial side is the axillary vein, separated from the artery by the medial cord of the brachial plexus and the medial anterior thoracic nerve; on the lateral side is the lateral cord of the brachial plexus. The brachial plexus thus surrounds the artery on three sides, and separates it from direct contact with the vein and adjacent muscles.

  The third portion of the axillary artery extends from the lower border of the Pectoralis minor to the lower border of the tendon of the Teres major. In front, it is covered by the lower part of the Pectoralis major above, but only by the integument and fascia below; behind, it is in relation with the lower part of the Subscapularis, and the tendons of the Latissimus dorsi and Teres major; on its lateral side is the Coracobrachialis, and on its medial or thoracic side, the axillary vein. The nerves of the brachial plexus bear the following relations to this part of the artery: on the lateral side are the lateral head and the trunk of the median, and the musculocutaneous for a short distance; on the medial side the ulnar (between the vein and artery) and medial brachial cutaneous (to the medial side of the vein); in front are the medial head of the median and the medial antibrachial cutaneous, and behind, the radial and axillary, the latter only as far as the lower border of the Subscapularis.

 

Collateral Circulation after Ligature of the Axillary Artery.—If the artery be tied above the origin of the thoracoacromial, the collateral circulation will be carried on by the same branches as after the ligature of the third part of the subclavian; if at a lower point, between the thoracoacromial and the subscapular, the latter vessel, by its free anastomosis with the transverse scapular and transverse cervical branches of the subclavian, will become the chief agent in carrying on the circulation; the lateral thoracic, if it be below the ligature, will materially contribute by its anastomoses with the intercostal and internal mammary arteries. If the point included in the ligature is below the origin of the subscapular artery, it will most probably also be below the origins of the two humeral circumflex arteries. The chief agents in restoring the circulation will then be the subscapular and the two humeral circumflex arteries anastomosing with the a. profunda brachii.

The scapular and circumflex arteries.

 

  The Scapular Circumflex Artery (a. circumflexa scapulæ; dorsalis scapulæ artery) is generally larger than the continuation of the subscapular. It curves around the axillary border of the scapula, traversing the space between the Subscapularis above, the Teres major below, and the long head of the Triceps laterally; it enters the infraspinatous fossa under cover of the Teres minor, and anastomoses with the transverse scapular artery and the descending branch of the transverse cervical. In its course it gives off two branches: one (infrascapular) enters the subscapular fossa beneath the Subscapularis, which it supplies, anastomosing with the transverse scapular artery and the descending branch of the transverse cervical; the other is continued along the axillary border of the scapula, between the Teres major and minor, and at the dorsal surface of the inferior angle anastomoses with the descending branch of the transverse cervical. In addition to these, small branches are distributed to the back part of the Deltoideus and the long head of the Triceps brachii, anastomosing with an ascending branch of the a. profunda brachii.

  5. The posterior humeral circumflex artery (a. circumflexa humeri posterior; posterior circumflex artery) arises from the axillary artery at the lower border of the Subscapularis, and runs backward with the axillary nerve through the quadrangular space bounded by the Subscapularis and Teres minor above, the Teres major below, the long head of the Triceps brachii medially, and the surgical neck of the humerus laterally. It winds around the neck of the humerus and is distributed to the Deltoideus and shoulder-joint, anastomosing with the anterior humeral circumflex and profunda brachii.

  6. The anterior humeral circumflex artery (a. circumflexa humeri anterior; anterior circumflex artery), considerably smaller than the posterior, arises nearly opposite it, from the lateral side of the axillary artery. It runs horizontally, beneath the Coracobrachialis and short head of the Biceps brachii, in front of the neck of the humerus. On reaching the intertubercular sulcus, it gives off a branch which ascends in the sulcus to supply the head of the humerus and the shoulder-joint. The trunk of the vessel is then continued onward beneath the long head of the Biceps brachii and the Deltoideus, and anastomoses with the posterior humeral circumflex artery.

 

Peculiarities.—The branches of the axillary artery vary considerably in different subjects. Occasionally the subscapular, humeral circumflex, and profunda arteries arise from a common trunk, and when this occurs the branches of the brachial plexus surround this trunk instead of the main vessel. Sometimes the axillary artery divides into the radial and ulnar arteries, and occasionally it gives origin to the volar interosseous artery of the forearm.

Brachial, ulnar and radial arteries, topography and branches on arm, forearm and hand

Brachial artery is immediate continuation of axillary artery and, starting to on level of inferior margin of major pectoral muscle, passes in medial biceps brachii sulcus, and in cubital fossa subdivides into its terminal branches are radial and ulnar.

Brachial artery gives off:

·          deep brachial artery - takes beginning from upper third of brachial artery, passes along the radial nerve in radial canal, where gives off the branches to posterior brachial muscles group and to deltoid muscle. Deep brachial artery ramifies into middle collateral artery, which anastomoses with recurrent interossea artery, and radial collateral artery, which anastomoses with radial recurrent artery;

·          superior ulnar collateral artery starts from brachial artery  beneath deep brachial artery and passes to posteriomedial surface of elbow joint, where anastomoses with posterior branch of ulnar recurrent artery;

·          inferior ulnar collateral artery starts from brachial artery in inferior its third, passes to anteriomedial surface of elbow joint, where anastomoses with anterior branch of ulnarої recurrent artery.

All named above collateral arteries, anastomosing with recurrent arteries, take part in forming of arterial cubital rete, from which blood supplies joint and muscles around it.  

Arteries of forearm and hand. Forearm and hand originate from terminal branches of brachial artery - radial and ulnar arteries.

Radial artery lies in radial anrebrachial sulcus and, rounding a styloid process of radius bone, passes on dorsal surface of hand, and then through the first interosseus space gets on palm, where its terminal portion, anastomosing with deep palmar branch from ulnar artery, makes deep palmar arc. Last gives off palmar metacarpeal arteries which anastomose with branches of superficial palmar arch  - common palmar digital arteries.

Radial artery gives off follow branches:

-         radial recurrent artery, which anastomoses with radial collateral artery;

-         superficial palmar branch, which anastomoses with terminal portion of ulnar artery, and muscular branches, which supply forearm muscles;

-         dorsal carpal branch and palmar carpal branch take hand in formation of dorsal carpal rete and palmar carpal rete;

-         first dorsal metacarpeal artery gives branches into three dorsal digital arteries, which feed dorsal surface of I and II fingers;

-         principal artery of pollex, which ramifies on three proper palmar digital arteries to I finger and radial side of palmar surface of ІІ finger. From dorsal carpal net four dorsal metacerpeal arteries start, each from which subdivides into two dorsal digital arteries. Last supply dorsal surfaces ІІ-V of fingers.

Ulnar artery lies into ulnar antebrachial sulcus and through the carpal canal gets on palm, where its terminal portion anastomoses with superficial palmar branch from radial artery and forms superficial palmar arc.

Ulnar artery gives off:

-         ulnar recurrent artery, which subdivides into anterior branch and posterior branch. They anastomose with collateral brachial arteries inferior and superior and take hand in formation of cubital articulate net (rete articulare cubiti);

-         common interossea artery, which divides into anterior interossea artery and posterior interossea artery. These arteries supply deep forearm muscles and take hand in formation of wrist nets. Recurrent interossea artery moves away from posterior interossea artery, then anastomoses with media collateral artery, and is take part in forming of cubital articulate net (rete articulare cubiti);

-         dorsal carpal branch and palmar carpal branch take hand in formation of dorsal carpal rete and palmar carpal rete;

-         deep palmar branch, which anastomoses with terminal portion of radial artery and takes hand in formation of deep palmar arc.

From superficial palmar arch three common palmar digital arteries move away, which ramify each on two proper palmar digital arteries.

From deep palmar arch 4 palmar metacarpeal arteries moves away, which fall into common palmar digital arteries and into principal artery of pollex in area of their division into proper palmar digital arteries.

 

 

The brachial artery

The brachial artery.

 

 

Varieties in Muscular Relations.—The brachial artery is occasionally concealed, in some part of its course, by muscular or tendinous slips derived from the Coracobrachialis, Biceps brachii, Brachialis, or Pronator teres.

 

Collateral Circulation.—After the application of a ligature to the brachial artery in the upper third of the arm, the circulation is carried on by branches from the humeral circumflex and subscapular arteries anastomosing with ascending branches from the profunda brachii. If the artery be tied below the origin of the profunda brachii and superior ulnar collateral, the circulation is maintained by the branches of these two arteries anastomosing with the inferior ulnar collateral, the radial and ulnar recurrents, and the dorsal interosseous.

 

Branches.—The branches of the brachial artery are:

Profunda Brachii.

Superior Ulnar Collateral.

Nutrient.

Inferior Ulnar Collateral.

Muscular.

  1. The arteria profunda brachii (superior profunda artery) is a large vessel which arises from the medial and back part of the brachial, just below the lower border of the Teres major. It follows closely the radial nerve, running at first backward between the medial and lateral heads of the Triceps brachii, then along the groove for the radial nerve, where it is covered by the lateral head of the Triceps brachii, to the lateral side of the arm; there it pierces the lateral intermuscular septum, and, descending between the Brachioradialis and the Brachialis to the front of the lateral epicondyle of the humerus, ends by anastomosing with the radial recurrent artery. It gives branches to the Deltoideus and to the muscles between which it lies; it supplies an occasional nutrient artery which enters the humerus behind the deltoid tuberosity. A branch ascends between the long and lateral heads of the Triceps brachii to anastomose with the posterior humeral circumflex artery; a middle collateral branch descends in the middle head of the Triceps brachii and assists in forming the anastomosis above the olecranon; and, lastly, a radial collateral branch runs down behind the lateral intermuscular septum to the back of the lateral epicondyle of the humerus, where it anastomoses with the interosseous recurrent and the inferior ulnar collateral arteries.

  2. The nutrient artery (a. nutricia humeri) of the body of the humerus arises about the middle of the arm and enters the nutrient canal near the insertion of the Coracobrachialis.

appears, from its direction, to be the continuation of the brachial, but it is smaller in caliber than the ulnar. It commences at the bifurcation of the brachial, just below the bend of the elbow, and passes along the radial side of the forearm to the wrist. It then winds backward, around the lateral side of the carpus, beneath the tendons of the Abductor pollicis longus and Extensores pollicis longus and brevis to the upper end of the space between the metacarpal bones of the thumb and index finger. Finally it passes forward between the two heads of the first Interosseous dorsalis, into the palm of the hand, where it crosses the metacarpal bones and at the ulnar side of the hand unites with the deep volar branch of the ulnar artery to form the deep volar arch. The radial artery therefore consists of three portions, one in the forearm, a second at the back of the wrist, and a third in the hand.

 

Relations.—(a) In the forearm the artery extends from the neck of the radius to the forepart of the styloid process, being placed to the medial side of the body of the bone above, and in front of it below. Its upper part is overlapped by the fleshy belly of the Brachioradialis; the rest of the artery is superficial, being covered by the integument and the superficial and deep fasciæ. In its course downward, it lies upon the tendon of the Biceps brachii, the Supinator, the Pronator teres, the radial origin of the Flexor digitorum sublimis, the Flexor pollicis longus, the Pronator quadratus, and the lower end of the radius. In the upper third of its course it lies between the Brachioradialis and the Pronator teres; in the lower two-thirds, between the tendons of the Brachioradialis and Flexor carpi radialis. The superficial branch of the radial nerve is close to the lateral side of the artery in the middle third of its course; and some filaments of the lateral antibrachial cutaneous nerve run along the lower part of the artery as it winds around the wrist. The vessel is accompanied by a pair of venæ comitantes throughout its whole course.

Ulnar and radial arteries. Deep view.

 

  (b) At the wrist the artery reaches the back of the carpus by passing between the radial collateral ligament of the wrist and the tendons of the Abductor pollicis longus and Extensor pollicis brevis. It then descends on the navicular and greater multangular bones, and before disappearing between the heads of the first Interosseus dorsalis is crossed by the tendon of the Extensor pollicis longus. In the interval between the two Extensores pollicis it is crossed by the digital rami of the superficial branch of the radial nerve which go to the thumb and index finger.

  (c) In the hand, it passes from the upper end of the first interosseous space, between the heads of the first Interosseus dorsalis, transversely across the palm between the Adductor pollicis obliquus and Adductor pollicis transversus, but sometimes piercing the latter muscle, to the base of the metacarpal bone of the little finger, where it anastomoses with the deep volar branch from the ulnar artery, completing the deep volar arch.

 

Peculiarities.—The origin of the radial artery is, in nearly one case in eight, higher than usual; more often it arises from the axillary or upper part of the brachial than from the lower part of the latter vessel. In the forearm it deviates less frequently from its normal position than the ulnar. It has been found lying on the deep fascia instead of beneath it. It has also been observed on the surface of the Brachioradialis, instead of under its medial border; and in turning around the wrist, it has been seen lying on, instead of beneath, the Extensor tendons of the thumb.

 

Branches.—The branches of the radial artery may be divided into three groups, corresponding with the three regions in which the vessel is situated.

In the Forearm.

At the Wrist.

In the Hand.

Radial Recurrent.     

Dorsal Carpal.

Princeps Pollicis.

Muscular.

First Dorsal Metacarpal.    

Volaris Indicis Radialis.

Volar Carpal.

Volar Metacarpal.

Superficial Volar.

Perforating.

Recurrent.

  The radial recurrent artery (a. recurrens radialis) arises immediately below the elbow. It ascends between the branches of the radial nerve, lying on the Supinator and then between the Brachioradialis and Brachialis, supplying these muscles and the elbow-joint, and anastomosing with the terminal part of the profunda brachii.

  The muscular branches (rami musculares) are distributed to the muscles on the radial side of the forearm.

  The volar carpal branch (ramus carpeus volaris; anterior radial carpal artery) is a small vessel which arises near the lower border of the Pronator quadratus, and, running across the front of the carpus, anastomoses with the volar carpal branch of the ulnar artery. This anastomosis is joined by a branch from the volar interosseous above, and by recurrent branches from the deep volar arch below, thus forming a volar carpal net-work which supplies the articulations of the wrist and carpus.

  The superficial volar branch (ramus volaris superficialis; superficialis volœ artery) arises from the radial artery, just where this vessel is about to wind around the lateral side of the wrist. Running forward, it passes through, occasionally over, the muscles of the ball of the thumb, which it supplies, and sometimes anastomoses with the terminal portion of the ulnar artery, completing the superficial volar arch. This vessel varies considerably in size: usually it is very small, and ends in the muscles of the thumb; sometimes it is as large as the continuation of the radial

  The dorsal carpal branch (ramus carpeus dorsalis; posterior radial carpal artery) is a small vessel which arises beneath the Extensor tendons of the thumb; crossing the carpus transversely toward the medial border of the hand, it anastomoses with the dorsal carpal branch of the ulnar and with the volar and dorsal interosseous arteries to form a dorsal carpal network. From this network are given off three slender dorsal metacarpal arteries, which run downward on the second, third, and fourth Interossei dorsales and bifurcate into the dorsal digital branches for the supply of the adjacent sides of the middle, ring, and little fingers respectively, communicating with the proper volar digital branches of the superficial volar arch. Near their origins they anastomose with the deep volar arch by the superior perforating arteries, and near their points of bifurcation with the common volar digital vessels of the superficial volar arch by the inferior perforating arteries.

  The first dorsal metacarpal arises just before the radial artery passes between the two heads of the first Interosseous dorsalis and divides almost immediately into two branches which supply the adjacent sides of the thumb and index finger; the radial side of the thumb receives a branch directly from the radial artery.

  The arteria princeps pollicis arises from the radial just as it turns medialward to the deep part of the hand; it descends between the first Interosseous dorsalis and Adductor pollicis obliquus, along the ulnar side of the metacarpal bone of the thumb to the base of the first phalanx, where it lies beneath the tendon of the Flexor pollicis longus and divides into two branches. These make their appearance between the medial and lateral insertions of the Adductor pollicis obliquus, and run along the sides of the thumb, forming on the volar surface of the last phalanx an arch, from which branches are distributed to the integument and subcutaneous tissue of the thumb.

  The arteria volaris indicis radialis (radialis indicis artery) arises close to the preceding, descends between the first Interosseus dorsalis and Adductor pollicis transversus, and runs along the radial side of the index finger to its extremity, where it anastomoses with the proper digital artery, supplying the ulnar side of the finger. At the lower border of the Adductor pollicis transversus this vessel anastomoses with the princeps pollicis, and gives a communicating branch to the superficial volar arch. The a. princeps pollicis and a. volaris indicis radialis may spring from a common trunk termed the first volar metacarpal artery.

  The deep volar arch (arcus volaris profundus; deep palmar arch) is formed by the anastomosis of the terminal part of the radial artery with the deep volar branch of the ulnar. It lies upon the carpal extremities of the metacarpal bones and on the Interossei, being covered by the Adductor pollicis obliquus, the Flexor tendons of the fingers, and the Lumbricales. Alongside of it, but running in the opposite direction—that is to say, toward the radial side of the hand—is the deep branch of the ulnar nerve.

  The volar metacarpal arteries (aa. metacarpeæ volares; palmar interosseous arteries), three or four in number, arise from the convexity of the deep volar arch; they run distally upon the Interossei, and anastomose at the clefts of the fingers with the common digital branches of the superficial volar arch.

  The perforating branches (rami perforantes), three in number, pass backward from the deep volar arch, through the second, third, and fourth interosseous spaces and between the heads of the corresponding Interossei dorsalis, to anastomose with the dorsal metacarpal arteries.

  The recurrent branches arise from the concavity of the deep volar arch. They ascend in front of the wrist, supply the intercarpal articulations, and end in the volar carpal network.

Theme 2. Superficial and deep veins, lymphatics of upper extremity

Subclavian vein continues from axillary vein, lies in same name sulcus of first rib and collects blood from thoracic veins and dorsal scapular vein.

Veins of upper limb are subdivided into superficial and deep. They are communicated by numerous anastomoses and have valves.

Superficial veins are developed richer than deep one.

Cephalic vein starts from radial part of dorsal venous hand net. From dorsal hand surface it passes on anterior surface of radial margin across forearm, lies into lateral biceps brachii sulcus, then into sulcus between deltoid and major pectoral muscles and empties under clavicle into axillarу vein.

Basilica vein collects blood from ulnar part of dorsal venous hand net, lies on ulnar side of anterior forearm surface, passes on medial biceps brachii sulcus and empties into one of brachial veins.

Intermediate cubiti vein passes obliquely in area of cubital fossa from cephalic to basilica veins.

The Deep veins of upper limb are double, they start from superficial palmar venous arch and deep palmar venous arch then accompanies same name arteries and.

Axillar vein is odd, it accompanies same name artery and continues into subclavian vein.

The veins of the upper extremity are divided into two sets, superficial and deep; the two sets anastomose frequently with each other. The superficial veins are placed immediately beneath the integument between the two layers of superficial fascia. The deep veins accompany the arteries, and constitute the venæ comitantes of those vessels. Both sets are provided with valves, which are more numerous in the deep than in the superficial veins.

 

The Superficial Veins of the Upper Extremity

  The superficial veins of the upper extremity are the digital, metacarpal, cephalic, basilic, median.

 

Digital Veins.—The dorsal digital veins pass along the sides of the fingers and are joined to one another by oblique communicating branches. Those from the adjacent sides of the fingers unite to form three dorsal metacarpal veins, which end in a dorsal venous net-work opposite the middle of the metacarpus. The radial part of the net-work is joined by the dorsal digital vein from the radial side of the index finger and by the dorsal digital veins of the thumb, and is prolonged upward as the cephalic vein. The ulnar part of the net-work receives the dorsal digital vein of the ulnar side of the little finger and is continued upward as the basilic vein. A communicating branch frequently connects the dorsal venous network with the cephalic vein about the middle of the forearm.

  The volar digital veins on each finger are connected to the dorsal digital veins by oblique intercapitular veins. They drain into a venous plexus which is situated over the thenar and hypothenar eminences and across the front of the wrist.

The superficial veins of the upper extremity.

 

  The median antibrachial vein (v. mediana antibrachii) drains the venous plexus on the volar surface of the hand. It ascends on the ulnar side of the front of the forearm and ends in the basilic vein or in the vena mediana cubiti; in a small proportion of cases it divides into two branches, one of which joins the basilic, the other the cephalic, below the elbow.

 

 

The Deep Veins of the Upper Extremity

  The deep veins follow the course of the arteries, forming their venæ comitantes. They are generally arranged in pairs, and are situated one on either side of the corresponding artery, and connected at intervals by short transverse branches.

 

Deep Veins of the Hand.—The superficial and deep volar arterial arches are each accompanied by a pair of venæ comitantes which constitute respectively the superficial and deep volar venous arches, and receive the veins corresponding to the branches of the arterial arches; thus the common volar digital veins, formed by the union of the proper volar digital veins, open into the superficial, and the volar metacarpal veins into the deep volar venous arches. The dorsal metacarpal veins receive perforating branches from the volar metacarpal veins and end in the radial veins and in the superficial veins on the dorsum of the wrist.

  The deep veins of the forearm are the venæ comitantes of the radial and ulnar veins and constitute respectively the upward continuations of the deep and superficial volar venous arches; they unite in front of the elbow to form the brachial veins. The radial veins are smaller than the ulnar and receive the dorsal metacarpal veins. The ulnar veins receive tributaries from the deep volar venous arches and communicate with the superficial veins at the wrist; near the elbow they receive the volar and dorsal interosseous veins and send a large communicating branch (profunda vein) to the vena mediana cubiti.

The veins of the right axilla, viewed from in front.

 

  The subclavian vein occasionally rises in the neck to a level with the third part of the subclavian artery, and occasionally passes with this vessel behind the Scalenus anterior.

 

Tributaries.—This vein receives the external jugular vein, sometimes the anterior jugular vein, and occasionally a small branch, which ascends in front of the clavicle, from the cephalic. At its angle of junction with the internal jugular, the left subclavian vein receives the thoracic duct, and the right subclavian vein the right lymphatic duct.

Lymphatic nodes of upper limb may be divided into two sets, superficial and deep.

The superficial vessels and nodes of upper limb pass along the course of vena basilica and vena cephalica and compose lateral, medial and middle groups. Lateral group of superficial vessels carries lymph from skin of I-ІІІ fingers, lateral forearm surface and arm to axillar lymphatic nodes. Medial group of superficial vessels carries lymph from IV-V fingers, hand, medial forearm side and brachium to cubital and axillar lymphatic nodes. Middle group carries lymph from palmar forearm surface to cubital fossa and here part of vessels joins to lateral grand, and part to medial group. The superficial lymphatic nodes accompany the superficial hand veins. They collect lymph from skin and subcutaneous tissue. From them lymph passes to cubital nodes and axillar nodes.

Deep vessels and nodes of upper limb accompany the deep big vessels and carry lymph into deep nodes and superficial nodes, and from here - into cubital nodes and axillar lymphatic nodes. Axillar nodes receive the vessels from upper limb, thoracic wall, and mammary gland. The efferent vessels from axillar nodes form a subclavian trunk (left and right).

The Lymph Nodes of the Upper Extremity.—The lymph nodes of the upper extremity are divided into two sets, superficial and deep.

The superficial lymph nodes are few and of small size. One or two supratrochlear nodes are placed above the medial epicondyle of the humerus, medial to the basilic vein. Their afferents drain the middle, ring, and little fingers, the medial portion of the hand, and the superficial area over the ulnar side of the forearm; these vessels are, however, in free communication with the other lymphatic vessels of the forearm. Their efferents accompany the basilic vein and join the deeper vessels. One or two deltoideopectoral nodes are found beside the cephalic vein, between the Pectoralis major and Deltoideus, immediately below the clavicle. They are situated in the course of the external collecting trunks of the arm.

Lymphatic vessels of the dorsal surface of the hand.

 

  The superficial lymphatic vessels commence in the lymphatic plexus which everywhere pervades the skin; the meshes of the plexus are much finer in the palm and on the flexor aspect of the digits than elsewhere. The digital plexuses are drained by a pair of vessels which run on the sides of each digit, and incline backward to reach the dorsum of the hand. From the dense plexus of the palm, vessels pass in different directions, viz., upward toward the wrist, downward to join the digital vessels, medialward to join the vessels on the ulnar border of the hand, and lateralward to those on the thumb. Several vessels from the central part of the plexus unite to form a trunk, which passes around the metacarpal bone of the index finger to join the vessels on the back of that digit and on the back of the thumb. Running upward in front of and behind the wrist, the lymphatic vessels are collected into radial, median, and ulnar groups, which accompany respectively the cephalic, median, and basilic veins in the forearm. A few of the ulnar lymphatics end in the supratrochlear nodes, but the majority pass directly to the lateral group of axillary nodes. Some of the radial vessels are collected into a trunk which ascends with the cephalic vein to the deltoideopectoral nodes; the efferents from this group pass either to the subclavicular axillary nodes or to the inferior cervical nodes.

Theme 3.  Brachial plexus, composition, topography

distribution of short branches.

The brachial plexus formed by the ventral rami of spinal nerves C₅-T₁. It lies on the deep neck muscles and is divided into a supraclavicular part and an infraclavicular part.

Supraclavicular Part passes through the interscalenus fora­men and consists of the superior, middle and inferior trunks and gives off motor nerves to the muscles of the shoulder girdle:

·        the dorsal scapular nerve (which supplies the levator scapulae muscle and the rhomboideus major and minor muscles),

·        the suprascapular nerve (supraspinatous muscle and infraspinatous muscle)

·        the subscapular nerve (passes to the subscapular and teres major muscle)

·        the subclavius nerve (to the subclavius muscle)

·        lateral and medial pectoral nerves (which supply the pectoralis major and pectoralis minor muscles)

·        the long thoracic nerve (whose branches supplies the serratus anterior muscle)

·        the thoracodorsal nerve (which sup­plies the latissimus dorsi muscle)

·        Axillary nerve branches off from posterior cord of the Infraclavicular Part. It passes deep in the axillary fossa through the quadrilaterum foramen to the back surface of the scapula. It supplies the capsule of the shoulder joint and gives off motor branches for deltoid and teres minor mus­cles. Branch superior lateral brachial cutaneous nerve passes to the skin, which it supplies the skin in the deltoid region.

 

The right brachial plexus with its short branches, viewed from in front. The Sternomastoid and Trapezius muscles have been completely, the Omohyoid and Subclavius have been partially, removed; a piece has been sawed out of the clavicle; the Pectoralis muscles have been incised and reflected.

 

Infraclavicular Part. According to relation to the axil­lary artery they distinguish the lateral cord, the medial cord and the posterior cord.

 

The Branchial Plexus (plexus brachialis)

The brachial plexus is formed by the union of the anterior divisions of the lower four cervical nerves and the greater part of the anterior division of the first thoracic nerve; the fourth cervical usually gives a branch to the fifth cervical, and the first thoracic frequently receives one from the second thoracic. The plexus extends from the lower part of the side of the neck to the axilla. The nerves which form it are nearly equal in size, but their mode of communication is subject to some variation. The following is, however, the most constant arrangement. The fifth and sixth cervical unite soon after their exit from the intervertebral foramina to form a trunk. The eighth cervical and first thoracic also unite to form one trunk, while the seventh cervical runs out alone. Three trunks—upper, middle, and lower—are thus formed, and, as they pass beneath the clavicle, each splits into an anterior and a posterior division.  The anterior divisions of the upper and middle trunks unite to form a cord, which is situated on the lateral side of the second part of the axillary artery, and is called the lateral cord or fasciculus of the plexus. The anterior division of the lower trunk passes down on the medial side of the axillary artery, and forms the medial cord or fasciculus of the brachial plexus. The posterior divisions of all three trunks unite to form the posterior cord or fasciculus of the plexus, which is situated behind the second portion of the axillary artery.

The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front. The Pectoralis major and minor muscles have been in large part removed; their attachments have been reflected.

 

Relations.—In the neck, the brachial plexus lies in the posterior triangle, being covered by the skin, Platysma, and deep fascia; it is crossed by the supraclavicular nerves, the inferior belly of the Omohyoideus, the external jugular vein, and the transverse cervical artery. It emerges between the Scaleni anterior and medius; its upper part lies above the third part of the subclavian artery, while the trunk formed by the union of the eighth cervical and first thoracic is placed behind the artery; the plexus next passes behind the clavicle, the Subclavius, and the transverse scapular vessels, and lies upon the first digitation of the Serratus anterior, and the Subscapularis. In the axilla it is placed lateral to the first portion of the axillary artery; it surrounds the second part of the artery, one cord lying medial to it, one lateral to it, and one behind it; at the lower part of the axilla it gives off its terminal branches to the upper limb.

 

Branches of Communication.—Close to their exit from the intervertebral foramina the fifth and sixth cervical nerves each receive a gray ramus communicans from the middle cervical ganglion of the sympathetic trunk, and the seventh and eighth cervical similar twigs from the inferior ganglion. The first thoracic nerve receives a gray ramus from, and contributes a white ramus to, the first thoracic ganglion. On the Scalenus anterior the phrenic nerve is joined by a branch from the fifth cervical.

 Branches of Distribution.—The branches of distribution of the brachial plexus may be arranged into two groups, viz., those given off above and those below the clavicle.

 Supraclavicular Branches.

 

 

   The Dorsal Scapular Nerve (n. dorsalis scapulæ; nerve to the Rhomboidei; posterior scapular nerve) arises from the fifth cervical, pierces the Scalenus medius, passes beneath the Levator scapulæ, to which it occasionally gives a twig, and ends in the Rhomboidei.

  The Suprascapular (n. suprascapularis) arises from the trunk formed by the union of the fifth and sixth cervical nerves. It runs lateralward beneath the Trapezius and the Omohyoideus, and enters the supraspinatous fossa through the suprascapular notch, below, the superior transverse scapular ligament; it then passes beneath the Supraspinatus, and curves around the lateral border of the spine of the scapula to the infraspinatous fossa. In the supraspinatous fossa it gives off two branches to the Supraspinatus muscle, and an articular filament to the shoulder-joint; and in the infraspinatous fossa it gives off two branches to the Infraspinatous muscle, besides some filaments to the shoulder-joint and scapula.

  The Nerve to the Subclavius (n. subclavius) is a small filament, which arises from the point of junction of the fifth and sixth cervical nerves; it descends to the muscle in front of the third part of the subclavian artery and the lower trunk of the plexus, and is usually connected by a filament with the phrenic nerve.

Suprascapular and axillary nerves of right side, seen from behind. (Testut.)

 

 

  The Long Thoracic Nerve (n. thoracalis longus; external respiratory nerve of Bell; posterior thoracic nerve) supplies the Serratus anterior. It usually arises by three roots from the fifth, sixth, and seventh cervical nerves; but the root from the seventh nerve may be absent. The roots from the fifth and sixth nerves pierce the Scalenus medius, while that from the seventh passes in front of the muscle. The nerve descends behind the brachial plexus and the axillary vessels, resting on the outer surface of the Serratus anterior. It extends along the side of the thorax to the lower border of that muscle, supplying filaments to each of its digitations.

  The branches for the Longus colli and Scaleni arise from the lower four cervical nerves at their exit from the intervertebral foramina.

 

Infraclavicular Branches.—The infraclavicular branches are derived from the three cords of the brachial plexus, but the fasciculi of the nerves may be traced through the plexus to the spinal nerves from which they originate. They are as follows:

 

  The Anterior Thoracic Nerves (nn. thoracales anteriores) supply the Pectorales major and minor.

  The lateral anterior thoracic (fasciculus lateralis) the larger of the two, arises from the lateral cord of the brachial plexus, and through it from the fifth, sixth, and seventh cervical nerves. It passes across the axillary artery and vein, pierces the coracoclavicular fascia, and is distributed to the deep surface of the Pectoralis major. It sends a filament to join the medial anterior thoracic and form with it a loop in front of the first part of the axillary artery.

  The medial anterior thoracic (fasciculus medialis) arises from the medial cord of the plexus and through it from the eighth cervical and first thoracic. It passes behind the first part of the axillary artery, curves forward between the axillary artery and vein, and unites in front of the artery with a filament from the lateral nerve. It then enters the deep surface of the Pectoralis minor, where it divides into a number of branches, which supply the muscle. Two or three branches pierce the muscle and end in the Pectoralis major.

  The Subscapular Nerves (nn. subscapulares), two in number, spring from the posterior cord of the plexus and through it from the fifth and sixth cervical nerves.

  The upper subscapular (short subscapular), the smaller enters the upper part of the Subscapularis, and is frequently represented by two branches.

  The lower subscapular supplies the lower part of the Subscapularis, and ends in the Teres major; the latter muscle is sometimes supplied by a separate branch.

  The Thoracodorsal Nerve (n. thoracodorsalis; middle or long subscapular nerve), a branch of the posterior cord of the plexus, derives its fibers from the fifth, sixth, and seventh cervical nerves; it follows the course of the subscapular artery, along the posterior wall of the axilla to the Latissimus dorsi, in which it may be traced as far as the lower border of the muscle.

   The Axillary Nerve (n. axillaris; circumflex nerve) arises from the posterior cord of the brachial plexus, and its fibers are derived from the fifth and sixth cervical nerves. It lies at first behind the axillary artery, and in front of the Subscapularis, and passes downward to the lower border of that muscle. It then winds backward, in company with the posterior humeral circumflex artery, through a quadrilateral space bounded above by the Subscapularis, below by the Teres major, medially by the long head of the Triceps brachii, and laterally by the surgical neck of the humerus, and divides into an anterior and a posterior branch.

  The anterior branch (upper branch) winds around the surgical neck of the humerus, beneath the Deltoideus, with the posterior humeral circumflex vessels, as far as the anterior border of that muscle, supplying it, and giving off a few small cutaneous branches, which pierce the muscle and ramify in the skin covering its lower part.

  The posterior branch (lower branch) supplies the Teres minor and the posterior part of the Deltoideus; upon the branch to the Teres minor an oval enlargement (pseudoganglion) usually exists. The posterior branch then pierces the deep fascia and is continued as the lateral brachial cutaneous nerve, which sweeps around the posterior border of the Deltoideus and supplies the skin over the lower two-thirds of the posterior part of this muscle, as well as that covering the long head of the Triceps brachii.

  The trunk of the axillary nerve gives off an articular filament which enters the shoulder-joint below the Subscapularis.

 

Long branches of brachial plexus, topography and distribution of branches on arm, forearm and hand

Nerves start from the medial cord:

1.     Me­dial cutaneous brachial nerve (supplies the skin of the ventromedial region of the brachium).

2.     Medial antebrachial cutaneous nerve (supplies the skin of the ventromedial region of the forearm).

3.     Ulnar nerve runs in the medial bicipital sulcus without (!) giving off any branches. It crosses the elbow joint on the backside in a medial epicondyle. Here the nerve may be felt and pressure on it produces an "elec­tric" type of pain which radiates to the ulnar side of the hand. The nerve passes in the ulnar sulcus on the forearm through the flexor carpi ulnaris muscle and then runs below this muscle to the wrist joint. It does not traverse the carpal tunnel but passes over the flexor retinaculum to the palmar surface of the hand where it divides into superficial and deep branches. In the forearm it gives off branches to the flexor carpi ulnaris muscle and to the ulnar half of the flexor digitorum profundus muscle. In the middle of the forearm a sensory branch is given off, the dorsal branch of the ulnar nerve, which passes to the ulnar side of the back of the hand where it supplies the skin. Another sensory branch, the palmar branch of the ulnar nerve, is given off in the distal third of the forearm. It passes to the palm of the hand and supplies the skin of the hypothenar eminence. The superficial branch, as the fourth com­mon palmar digital nerve, passes to the interosseous space between the ring and little fingers and divides into the proper palmar digital nerves, which supply the sensory innervation of the volar surface of the little finger and the ulnar side of 4-th finger. The deep branch gives off branches to all the muscles of the hypothenar eminence (abductor muscle of the fifth finger, the flexor brevis muscle of the minimus finger, and the opponens muscle of the minimus finger) and all the dorsal and palmar interosseous muscles, the third and fourth lumbrical muscles, the adductor pollicis muscle, and the deep head of the flexor pollicis brevis muscle.

4.     Median nerve is formed on the anterior surface of the axillary artery by parts of the medial and lateral cords. The nerve runs to the elbow in the medial bicipital sulcus and does not (!) supply anything in brachial region. Then it reaches the forearm between the two heads of the pronator teres muscle. It extends to the wrist between the flexor digitorum superficialis and the flexor digitorum profundusin median sulcus. Before it enters the carpal canal it lies superficially be­tween the tendons of the flexor carpi radialis muscle and the palmaris longus. In the carpal canal it divides into its terminal branches. The muscular branches of the nerve supply the pronators and most of the flexors of the forearm: pronator teres, the flexor carpi radialis, the palmaris longus and the flexor digitorum superficialis muscle. The anterior antebrachial interosseous nerve runs on the interosseous mem­brane to the deep muscles. In the lower third of the forearm, the sensory palmar branch of the median nerve passes to the skin of the ball of the thumb, the radial side of the wrist and the palm of the hand. The median nerve gives off branches to the periosteum, the elbow joint, the radiocarpal joint and the mediocarpal joint. After passing through the carpal canal the median nerve divides into the common palmar digital nerves I, II, III, each of which divide at the level of the proximal metacarpophalangeal joints into the two proper palmar digital nerves. They give off a branch to the thenar muscles (abduc­tor pollicis brevis muscle, superfi­cial head of the flexor pollicis brevis muscle and the opponens pollicis muscle). The common palmar digital nerves supply the I-II lumbrical muscles. Sensory branches supply the skin of thenar, of the 1^st,  2^d, 3^d and part of the 4^th fingers.

h

Carpal Tunnel Syndrome

Carpal tunnel syndrome is a condition that causes a "needles-and- pins" sensation to the index and middle finger of the wrist, and is caused by compression or stretching of the medial nerve. It is a common disorder with people whose occupation require a great deal of wrist flexion or prolonged extension. It has been commonly called the "secretary's disease" and is seen commonly in writers, typists, pianists, and even more recently, computer professions. The symptoms can vary, but usually include pain in the middle area of the wrist, swelling of wrist, numbness or tingling in index and middle fingers, and loss of function of hand in severe cases. Splints applied to dorsiflex the wrist occasionally help. Cortisone injections may help, and surgery to strip away build-up of adhesive tissue may be required. This condition can recur even after treatment and tends to worsen in the evening and night.

Cutaneous nerves of right upper extremity. Anterior view.

 

 

Beside the Median nerve Musculocutaneous nerve also start from the lateral cord. The nerve runs through the coraco-brachialis muscle between the biceps and brachialis muscles (and nerve supplies them) as far as the elbow. The sensory fibers of the nerve at the elbow pass through the fascia onto the surface and, as the lateral antebrachial cutaneous nerve, supply the skin in the lateral part of the forearm.

 

The posterior cord gives off the axillary and radial nerves.

Radial nerve runs from the axilla in the radial canal and supplies the long, lateral and medial heads of the triceps brachii and anconaeus mus­cles. Also inferior lateral and posterior brachial cutaneous nerves pass to the skin, which it supplies on the lateral and posterior surface of the arm. Radial nerve crosses the elbow joint and di­vides at the level of the head of the radius into its two terminal branches, the superficial and deep branch. The deep branch gives off numerous muscular branches and fi­nally extends to the wrist joint as the posterior antebrachial interosseous nerve. Radial nerve supplies all superficial and deep posterior antebrachial mus­cles, brachioradialis mus­cles, also skin in posterior region. On the back of the hand the superficial branch gives off the 5 dorsal digital nerves which supply the only skin of radial part of the hand, the back surface of the 1^st, 2^nd, 3^d fingers.

 

 

Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Anterior view.

 

 

 

  The Musculocutaneous Nerve (n. musculocutaneus) arises from the lateral cord of the brachial plexus, opposite the lower border of the Pectoralis minor, its fibers being derived from the fifth, sixth, and seventh cervical nerves. It pierces the Coracobrachialis muscle and passes obliquely between the Biceps brachii and the Brachialis, to the lateral side of the arm; a little above the elbow it pierces the deep fascia lateral to the tendon of the Biceps brachii and is continued into the forearm as the lateral antibrachial cutaneous nerve. In its course through the arm it supplies the Coracobrachialis, Biceps brachii, and the greater part of the Brachialis. The branch to the Coracobrachialis is given off from the nerve close to its origin, and in some instances as a separate filament from the lateral cord of the plexus; it is derived from the seventh, cervical nerve. The branches to the Biceps brachii and Brachialis are given off after the musculocutaneous has pierced the Coracobrachialis; that supplying the Brachialis gives a filament to the elbow-joint. The nerve also sends a small branch to the bone, which enters the nutrient foramen with the accompanying artery.

 

 

Cutaneous nerves of right upper extremity. Posterior view.

 

Diagram of segmental distribution of the cutaneous nerves of the right upper extremity. Posterior view.

 

  The lateral antibrachial cutaneous nerve (n. cutaneus antibrachii cutaneous lateralis; branch of musculocutaneous nerve) passes behind the cephalic vein, and divides, opposite the elbow-joint, into a volar and a dorsal branch.

  The volar branch (ramus volaris; anterior branch) descends along the radial border of the forearm to the wrist, and supplies the skin over the lateral half of its volar surface. At the wrist-joint it is placed in front of the radial artery, and some filaments, piercing the deep fascia, accompany that vessel to the dorsal surface of the carpus. The nerve then passes downward to the ball of the thumb, where it ends in cutaneous filaments. It communicates with the superficial branch of the radial nerve, and with the palmar cutaneous branch of the median nerve.

  The dorsal branch (ramus dorsalis; posterior branch) descends, along the dorsal surface of the radial side of the forearm to the wrist. It supplies the skin of the lower two-thirds of the dorso-lateral surface of the forearm, communicating with the superficial branch of the radial nerve and the dorsal antibrachial cutaneous branch of the radial.

  The musculocutaneous nerve presents frequent irregularities. It may adhere for some distance to the median and then pass outward, beneath the Biceps brachii, instead of through the Coracobrachialis. Some of the fibers of the median may run for some distance in the musculocutaneous and then leave it to join their proper trunk; less frequently the reverse is the case, and the median sends a branch to join the musculocutaneous. The nerve may pass under the Coracobrachialis or through the Biceps brachii. Occasionally it gives a filament to the Pronator teres, and it supplies the dorsal surface of the thumb when the superficial branch of the radial nerve is absent.

  The Medial Antibrachial Cutaneous Nerve (n. cutaneus antibrachii medialis; internal cutaneous nerve) arises from the medial cord of the brachial plexus. It derives its fibers from the eighth cervical and first thoracic nerves, and at its commencement is placed medial to the axillary artery. It gives off, near the axilla, a filament, which pierces the fascia and supplies the integument covering the Biceps brachii, nearly as far as the elbow. The nerve then runs down the ulnar side of the arm medial to the brachial artery, pierces the deep fascia with the basilic vein, about the middle of the arm, and divides into a volar and an ulnar branch.

  The volar branch (ramus volaris; anterior branch), the larger, passes usually in front of, but occasionally behind, the vena mediana cubiti (median basilic vein). It then descends on the front of the ulnar side of the forearm, distributing filaments to the skin as far as the wrist, and communicating with the palmar cutaneous branch of the ulnar nerve (811).

  The ulnar branch (ramus ulnaris; posterior branch) passes obliquely downward on the medial side of the basilic vein, in front of the medial epicondyle of the humerus, to the back of the forearm, and descends on its ulnar side as far as the wrist, distributing filaments to the skin. It communicates with the medial brachial cutaneous, the dorsal antibrachial cutaneous branch of the radial, and the dorsal branch of the ulnar.

  The Medial Brachial Cutaneous Nerve (n. cutaneus brachii medialis; lesser internal cutaneous nerve; nerve of Wrisberg) is distributed to the skin on the ulnar side of the arm. It is the smallest branch of the brachial plexus, and arising from the medial cord receives its fibers from the eighth cervical and first thoracic nerves. It passes through the axilla, at first lying behind, and then medial to the axillary vein, and communicates with the intercostobrachial nerve. It descends along the medial side of the brachial artery to the middle of the arm, where it pierces the deep fascia, and is distributed to the skin of the back of the lower third of the arm, extending as far as the elbow, where some filaments are lost in the skin in front of the medial epicondyle, and others over the olecranon. It communicates with the ulnar branch of the medial antibrachial cutaneous nerve.

  In some cases the medial brachial cutaneous and intercostobrachial are connected by two or three filaments, which form a plexus in the axilla. In other cases the intercostobrachial is of large size, and takes the place of the medial brachial cutaneous, receiving merely a filament of communication from the brachial plexus, which represents the latter nerve; in a few cases, this filament is wanting.

  The Median Nerve (n. medianus) extends along the middle of the arm and forearm to the hand. It arises by two roots, one from the lateral and one from the medial cord of the brachial plexus; these embrace the lower part of the axillary artery, uniting either in front of or lateral to that vessel. Its fibers are derived from the sixth, seventh, and eighth cervical and first thoracic nerves. As it descends through the arm, it lies at first lateral to the brachial artery; about the level of the insertion of the Coracobrachialis it crosses the artery, usually in front of, but occasionally behind it, and lies on its medial side at the bend of the elbow, where it is situated behind the lacertus fibrosus (bicipital fascia), and is separated from the elbow-joint by the Brachialis. In the forearm it passes between the two heads of the Pronator teres and crosses the ulnar artery, but is separated from this vessel by the deep head of the Pronator teres. It descends beneath the Flexor digitorum sublimis, lying on the Flexor digitorum profundus, to within 5 cm. of the transverse carpal ligament; here it becomes more superficial, and is situated between the tendons of the Flexor digitorum sublimis and Flexor carpi radialis. In this situation it lies behind, and rather to the radial side of, the tendon of the Palmaris longus, and is covered by the skin and fascia. It then passes behind the transverse carpal ligament into the palm of the hand. In its course through the forearm it is accompanied by the median artery, a branch of the volar interroseous artery.

 

Branches. With the exception of the nerve to the Pronator teres, which sometimes arises above the elbow-joint, the median nerve gives off no branches in the arm. As it passes in front of the elbow, it supplies one or two twigs to the joint.

  In the forearm its branches are: muscular, volar interosseous, and palmar.

  The muscular branches (rami musculares) are derived from the nerve near the elbow and supply all the superficial muscles on the front of the forearm, except the Flexor carpi ulnaris.

  The volar interosseous nerve (n. interosseus [antibrachii] volaris; anterior interosseous nerve) supplies the deep muscles on the front of the forearm, except the ulnar half of the Flexor digitorum profundus. It accompanies the volar interosseous artery along the front of the interosseous membrane, in the interval between the Flexor pollicis longus and Flexor digitorum profundus, supplying the whole of the former and the radial half of the latter, and ending below in the Pronator quadratus and wrist-joint.

  The palmar branch (ramus cutaneus palmaris n. mediani) of the median nerve arises at the lower part of the forearm. It pierces the volar carpal ligament, and divides into a lateral and a medial branch; the lateral branch supplies the skin over the ball of the thumb, and communicates with the volar branch of the lateral antibrachial cutaneous nerve; the medial branch supplies the skin of the palm and communicates with the palmar cutaneous branch of the ulnar.

  In the palm of the hand the median nerve is covered by the skin and the palmar aponeurosis, and rests on the tendons of the Flexor muscles. Immediately after emerging from under the transverse carpal ligament the nerve becomes enlarged and flattened and splits into a smaller, lateral, and a larger, medial portion. The lateral portion supplies a short, stout branch to certain of the muscles of the ball of the thumb, viz., the Abductor brevis, the Opponens, and the superficial head of the Flexor brevis, and then divides into three proper volar digital nerves; two of these supply the sides of the thumb, while the third gives a twig to the first Lumbricalis and is distributed to the radial side of the index finger. The medial portion of the nerve divides into two common volar digital nerves. The first of these gives a twig to the second Lumbricalis and runs toward the cleft between the index and middle fingers, where it divides into two proper digital nerves for the adjoining sides of these digits; the second runs toward the cleft between the middle and ring fingers, and splits into two proper digital nerves for the adjoining sides of these digits; it communicates with a branch from the ulnar nerve and sometimes sends a twig to the third Lumbricalis.

  Each proper digital nerve, opposite the base of the first phalanx, gives off a dorsal branch which joins the dorsal digital nerve from the superficial branch of the radial nerve, and supplies the integument on the dorsal aspect of the last phalanx. At the end of the digit, the proper digital nerve divides into two branches, one of which supplies the pulp of the finger, the other ramifies around and beneath the nail. The proper digital nerves, as they run along the fingers, are placed superficial to the corresponding arteries.

Nerves of the left upper extremity.

 

The Ulnar Nerve (n. ulnaris) is placed along the medial side of the limb, and is distributed to the muscles and skin of the forearm and hand. It arises from the medial cord of the brachial plexus, and derives its fibers from the eighth cervical and first thoracic nerves. It is smaller than the median, and lies at first behind it, but diverges from it in its course down the arm. At its origin it lies medial to the axillary artery, and bears the same relation to the brachial artery as far as the middle of the arm. Here it pierces the medial intermuscular septum, runs obliquely across the medial head of the Triceps brachii, and descends to the groove between the medial epicondyle and the olecranon, accompanied by the superior ulnar collateral artery. At the elbow, it rests upon the back of the medial epicondyle, and enters the forearm between the two heads of the Flexor carpi ulnaris. In the forearm, it descends along the ulnar side lying upon the Flexor digitorum profundus; its upper half is covered by the Flexor carpi ulnaris, its lower half lies on the lateral side of the muscle, covered by the integument and fascia. In the upper third of the forearm, it is separated from the ulnar artery by a considerable interval, but in the rest of its extent lies close to the medial side of the artery. About 5 cm. above the wrist it ends by dividing into a dorsal and a volar branch.

Deep palmar nerves.

 

  The branches of the ulnar nerve are: articular to the elbow-joint, muscular, palmar cutaneous, dorsal, and volar.

  The articular branches to the elbow-joint are several small filaments which arise from the nerve as it lies in the groove between the medial epicondyle and olecranon.

  The muscular branches (rami musculares) two in number, arise near the elbow: one supplies the Flexor carpi ulnaris; the other, the ulnar half of the Flexor digitorum profundus.

  The palmar cutaneous branch (ramus cutaneus palmaris) arises about the middle of the forearm, and descends on the ulnar artery, giving off some filaments to the vessel. It perforates the volar carpal ligament and ends in the skin of the palm, communicating with the palmar branch of the median nerve.

  The dorsal branch (ramus dorsalis manus) arises about 5 cm. above the wrist; it passes backward beneath the Flexor carpi ulnaris, perforates the deep fascia, and, running along the ulnar side of the back of the wrist and hand, divides into two dorsal digital branches; one supplies the ulnar side of the little finger; the other, the adjacent sides of the little and ring fingers. It also sends a twig to join that given by the superficial branch of the radial nerve for the adjoining sides of the middle and ring fingers, and assists in supplying them. A branch is distributed to the metacarpal region of the hand, communicating with a twig of the superficial branch of the radial nerve.

The suprascapular, axillary, and radial nerves.

 

  On the little finger the dorsal digital branches extend only as far as the base of the terminal phalanx, and on the ring finger as far as the base of the second phalanx; the more distal parts of these digits are supplied by dorsal branches derived from the proper volar digital branches of the ulnar nerve.

  The volar branch (ramus volaris manus) crosses the transverse carpal ligament on the lateral side of the pisiform bone, medial to and a little behind the ulnar artery. It ends by dividing into a superficial and a deep branch.

  The superficial branch (ramus superficialis [n. ulnaris] supplies the Palmaris brevis, and the skin on the ulnar side of the hand, and divides into a proper volar digital branch for the ulnar side of the little finger, and a common volar digital branch which gives a communicating twig to the median nerve and divides into two proper digital nerves for the adjoining sides of the little and ring fingers.The proper digital branches are distributed to the fingers in the same manner as those of the median.

  The deep branch (ramus profundus) accompanied by the deep branch of the ulnar artery, passes between the Abductor digiti quinti and Flexor digiti quinti brevis; it then perforates the Opponens digiti quinti and follows the course of the deep volar arch beneath the Flexor tendons. At its origin it supplies the three short muscles of the little finger. As it crosses the deep part of the hand, it supplies all the Interossei and the third and fourth Lumbricales; it ends by supplying the Adductores pollicis and the medial head of the Flexor pollicis brevis. It also sends articular filaments to the wrist-joint.

  It has been pointed out that the ulnar part of the Flexor digitorum profundus is supplied by the ulnar nerve; the third and fourth Lumbricales, which are connected with the tendons of this part of the muscle, are supplied by the same nerve. In like manner the lateral part of the Flexor digitorum profundus and the first and second Lumbricales are supplied by the median nerve; the third Lumbricalis frequently receives an additional twig from the median nerve.

  The Radial Nerve (n. radialis; musculospiral nerve) the largest branch of the brachial plexus, is the continuation of the posterior cord of the plexus. Its fibres are derived from the fifth, sixth, seventh, and eighth cervical and first thoracic nerves. It descends behind the first part of the axillary artery and the upper part of the brachial artery, and in front of the tendons of the Latissimus dorsi and Teres major. It then winds around from the medial to the lateral side of the humerus in a groove with the a. profunda brachii, between the medial and lateral heads of the Triceps brachii. It pierces the lateral intermuscular septum, and passes between the Brachialis and Brachioradialis to the front of the lateral epicondyle, where it divides into a superficial and a deep branch.

The branches of the musculospiral nerve are:

Muscular.

Superficial.

Cutaneous.

Deep.

  The muscular branches (rami musculares) supply the Triceps brachii, Anconæus, Brachioradialis, Extensor carpi radialis longus, and Brachialis, and are grouped as medial, posterior, and lateral.

  The medial muscular branches supply the medial and long heads of the Triceps brachii. That to the medial head is a long, slender filament, which lies close to the ulnar nerve as far as the lower third of the arm, and is therefore frequently spoken of as the ulnar collateral nerve.

  The posterior muscular branch, of large size, arises from the nerve in the groove between the Triceps brachii and the humerus. It divides into filaments, which supply the medial and lateral heads of the Triceps brachii and the Anconæus muscles. The branch for the latter muscle is a long, slender filament, which descends in the substance of the medial head of the Triceps brachii.

  The lateral muscular branches supply the Brachioradialis, Extensor carpi radialis longus, and the lateral part of the Brachialis.

  The cutaneous branches are two in number, the posterior brachial cutaneous and the dorsal antibrachial cutaneous.

  The posterior brachial cutaneous nerve (n. cutaneus brachii posterior; internal cutaneous branch of musculospiral) arises in the axilla, with the medial muscular branch. It is of small size, and passes through the axilla to the medial side of the area supplying the skin on its dorsal surface nearly as far as the olecranon. In its course it crosses behind, and communicates with, the intercostobrachial.

  The dorsal antibrachial cutaneous nerve (n. cutaneus antibrachii dorsalis; external cutaneous branch of musculospiral) perforates the lateral head of the Triceps brachii at its attachment to the humerus. The upper and smaller branch of the nerve passes to the front of the elbow, lying close to the cephalic vein, and supplies the skin of the lower half of the arm. The lower branch pierces the deep fascia below the insertion of the Deltoideus, and descends along the lateral side of the arm and elbow, and then along the back of the forearm to the wrist, supplying the skin in its course, and joining, near its termination, with the dorsal branch of the lateral antibrachial cutaneous nerve.

  The Superficial Branch of the Radial Nerve (ramus superficialis radial nerve) passes along the front of the radial side of the forearm to the commencement of its lower third. It lies at first slightly lateral to the radial artery, concealed beneath the Brachioradialis. In the middle third of the forearm, it lies behind the same muscle, close to the lateral side of the artery. It quits the artery about 7 cm. above the wrist, passes beneath the tendon of the Brachioradialis, and, piercing the deep fascia, divides into two branches.

  The lateral branch, the smaller, supplies the skin of the radial side and ball of the thumb, joining with the volar branch of the lateral antibrachial cutaneous nerve.

  The medial branch communicates, above the wrist, with the dorsal branch of the lateral antibrachial cutaneous, and, on the back of the hand, with the dorsal branch of the ulnar nerve. It then divides into four digital nerves, which are distributed as follows: the first supplies the ulnar side of the thumb; the second, the radial side of the index finger; the third, the adjoining sides of the index and middle fingers; the fourth communicates with a filament from the dorsal branch of the ulnar nerve, and supplies the adjacent sides of the middle and ring fingers.

  The Deep Branch of the Radial Nerve (n. interosseus dorsalis; dorsal or posterior interosseous nerve) winds to the back of the forearm around the lateral side of the radius between the two planes of fibers of the Supinator, and is prolonged downward between the superficial and deep layers of muscles, to the middle of the forearm. Considerably diminished in size, it descends, as the dorsal interosseous nerve, on the interosseous membrane, in front of the Extensor pollicis longus, to the back of the carpus, where it presents a gangliform enlargement from which filaments are distributed to the ligaments and articulations of the carpus. It supplies all the muscles on the radial side and dorsal surface of the forearm, excepting the Anconæus, Brachioradialis, and Extenosr carpi radialis longus.

Prepared by

Reminetskyy B.Y.