Lecture
endocrine
glands
There
are certain organs which are very similar to secreting glands, but differ from
them in one essential particular, viz., they do not possess any ducts by which their
secretion is discharged. These organs are known as endocrine glands. They are capable of internal secretion—that is to say, of forming, from materials
brought to them in the blood, substances which have a certain influence upon
the nutritive and other changes going on in the body. This secretion is carried
into the blood stream, either directly by the veins or indirectly through the
medium of the lymphatics.
These glands include the thyroid, the parathyroids
and the thymus; the pituitary body and the pineal body; the chromaphil and
cortical systems to which belong the suprarenals,
the paraganglia and aortic glands, the glomus caroticum and perhaps the glomus coccygeum. The spleen
is usually included in this list and sometimes the lymph and hemolymph nodes
described with the lymphatic system. Other glands as the liver, pancreas and
sexual glands give off internal secretions, as do the gastric and intestinal
mucous membranes.
ENDOCRINE GLANDS do not have
the ducts, their secret gets immediately into blood. They have prettily
abundant blood supplying, and their secret has special chemical and
physiological activity. Endocrine system for origin subdivides into glands with
endodermal, mesodermal or ektodermal origin.
Glands
of endodermal origin subdivide
into bronchiogenic group (thyroid, parathyroid and thymus glands) and glands
developed from epithelium of intestinal tube (endocrine part of pancreas).
Glands
of mesodermal origin
(interrenal system) include interstitial cells of sexual glands and cortex of
adrenal glands.
Glands
of ectoderm group include
hypophysis (neurogenic group) and medulla of suprarenal glands and paraganglia.
The Thyroid gland is situated in anterior neck area on level
of the IV-VI cervical vertebrae and consists of right and left lobes communicated by isthmus, which continues upward by pyramidal portion. Thyroid gland is
built by parenchyma, which subdivides into lobuli by septa. Follicles are
situated in lobules, which contain hormones of thyroid gland: thyroxine, triiodthyronin,
calcitonin. They influence on all types of metabolism.
The Parathyroid gland has pair superior parathyroid gland
and inferior parathyroid gland that situated on back surface of thyroid gland.
Accessory parathyroid glands can be present. Parathyroid gland excretes
parathyroid hormone that regulates metabolism of phosphorus and calcium.
The Thymus is a central organ of immune system, which is
situated in anterior mediastinum on level of the 4th ribs behind manubrium
sterni. Behind thymus pericardium is situated. Thymus gland consists of lobes -
right and left, which have the lobule that built by cortex and medulla of
thymus gland. In medulla Ò-lymphocyte matter acquire that peculiarities which
contribute to protective function.
Endocrine
part of sexual glands (testicle
and ovary)
Interstitial (Leidig) cells are situated in parenchyma of testicle. They
excrete testosteron, which influences
on development of secondary sexual signs. Corpus luteum positioned in ovaric
parenchyma produces a progesteron (it
prepares a mucous membrane of the uterus membrane to embryo fixation, detains
development of new follicles and stimulates development of mammary glands
during pregnancy). Follicular epithelium excretes estrogen, which contributes to development of primary female sexual
signs (ovary and uterus) also development of secondary female sexual signs, as
growth of mammary gland, hair according female type cetera and assists the
regulation of menses.
Endocrine
part of pancreas is
represented by islets of Langerhans.
They produce insulin and glucagon, that regulate metabolism of
carbohydrates, regulative a sugar contents in organism. Attached to
insufficient production of these hormonal disease sugar diabetes arises.
The Adrenal gland is a pair endocrine gland, which lies on
superior extremity of right and left kidneys on level of the Th 11 – Th 12
vertebrae. Each adrenal gland has triangle shape and has anterior surface,
posterior surface and renal surface and superior margin and medial margin, and
also has the hilus and consists of cortex and medulla matter. Cortex produces
mineralocorticoids (aldosterone), glucocorticoids and androgens. Medulla of
adrenal glands produces adrenalin and noradrenalin.
The
Paraganglia
are small agglomerations of chromaffin cells, placed closely near abdominal
aorta (aortic paraganglia) or in thickness of sympathetic trunk (sympathetic
paraganglion). Paraganglia has a function, analogic to function of medulla
suprarenal gland.
a. The Thyroid Gland (Glandula
Thyreiodea) is a highly vascular organ, situated at the
front and sides of the neck; it consists of right and left lobes connected
across the middle line by a narrow portion, the isthmus. Its weight is somewhat variable, but is usually about
The
lobes (lobuli gl. Thyreoideæ) are conical in shape, the apex of each
being directed upward and lateralward as far as the junction of the middle with
the lower third of the thyroid cartilage; the base looks downward, and is on a
level with the fifth or sixth tracheal ring. Each lobe is about
The
isthmus (isthmus gl. thyreoidea) connects together the lower thirds of the
lobes; it measures about
A
third lobe, of conical shape, called the pyramidal
lobe, frequently arises from the
upper part of the isthmus, or from the adjacent portion of either lobe, but
most commonly the left, and ascends as far as the hyoid bone. It is
occasionally quite detached, or may be divided into two or more parts.
A
fibrous or muscular band is sometimes found attached, above, to the body of the
hyoid bone, and below to the isthmus of the gland, or its pyramidal lobe. When
muscular, it is termed the Levator
glandulæ thyreoideæ.
Small
detached portions of thyroid tissue are sometimes found in the vicinity of the
lateral lobes or above the isthmus; they are called accessory thyroid glands (glandulæ
thyreoideæ accessoriæ).
Development.—The
thyroid gland is developed from a median diverticulum, which appears about the fourth
week on the summit of the tuberculum impar, but later is found in the furrow
immediately behind the tuberculum. It grows
downward and backward as a tubular duct, which bifurcates and subsequently
subdivides into a series of cellular cords, from which the isthmus and lateral
lobes of the thyroid gland are developed. The ultimo-branchial bodies from the
fifth pharyngeal pouches are enveloped by the lateral lobes of the thyroid gland;
they undergo atrophy and do not form true thyroid tissue. The connection of the
diverticulum with the pharynx is termed the thyroglossal duct; its continuity is subsequently interrupted, and
it undergoes degeneration, its upper end being represented by the foramen cecum
of the tongue, and its lower by the pyramidal lobe of the thyroid gland.
Structure.—The
thyroid gland is invested by a thin capsule of connective tissue, which
projects into its substance and imperfectly divides it into masses of irregular
form and size. When the organ is cut into, it is of a brownish-red color, and
is seen to be made up of a number of closed vesicles, containing a yellow
glairy fluid, and separated from each other by intermediate connective tissue.
The
vesicles of the thyroid of the adult animal are generally closed spherical
sacs; but in some young animals, e. g.,
young dogs, the vesicles are more or less tubular and branched. This appearance
is supposed to be due to the mode of growth of the gland, and merely indicates
that an increase in the number of vesicles is taking place. Each vesicle is
lined by a single layer of cubical epithelium. There does not appear to be a
basement membrane, so that the epithelial cells are in direct contact with the
connective-tissue reticulum which supports the acini. The vesicles are of
various sizes and shapes, and contain as a normal product a viscid,
homogeneous, semifluid, slightly yellowish, colloid material; red corpuscles
are found in it in various stages of disintegration and decolorization, the
yellow tinge being probably due to the hemoglobin, which is thus set free from
the colored corpuscles. The colloid material contains an iodine compound, iodothyrin, and is readily stained by
eosin. According to Bensley the thyroid gland prepares and secretes into the
vascular channels a substance, formed under normal conditions in the outer pole
of the cell and excreted from it directly without passing by the indirect route
through the follicular cavity. In addition to this direct mode of secretion
there is an indirect mode which consists in the condensation of the secretion
into the form of droplets, having high content of solids, and the extension of
these droplets into the follicular cavity. These droplets are formed in the
same zone of the cell as that in which the primary or direct secretion is
formed.
This
internal secretion of the thyroid is supposed to contain a specific hormone
which acts as a chemical stimulus to other tissues, increasing their
metabolism.
Vessels and Nerves.—The
arteries supplying the thyroid gland
are the superior and inferior thyroids and sometimes an additional branch
(thyroidea ima) from the innominate artery or the arch of the aorta, which
ascends upon the front of the trachea. The arteries are remarkable for their
large size and frequent anastomoses. The veins
form a plexus on the surface of the gland and on the front of the trachea; from
this plexus the superior, middle, and inferior thyroid veins arise; the
superior and middle end in the internal jugular, the inferior in the innominate
vein. The capillary bloodvessels form a dense plexus in the connective tissue
around the vesicles, between the epithelium of the vesicles and the endothelium
of the lymphatics, which surround a greater or smaller part of the
circumference of the vesicle. The lymphatic
vessels run in the interlobular connective tissue, not uncommonly
surrounding the arteries which they accompany, and communicate with a net-work
in the capsule of the gland; they may contain colloid material. They end in the
thoracic and right lymphatic trunks. The nerves
are derived from the middle and inferior cervical ganglia of the sympathetic.
The
parathyroid glands are small
brownish-red bodies, situated as a rule between the posterior borders of the
lateral lobes of the thyroid gland and its capsule. They differ from it in
structure, being composed of masses of cells arranged in a more or less
columnar fashion with numerous intervening capillaries. They measure on an
average about
Development.—The
parathyroid bodies are developed as outgrowths from the third and fourth
branchial pouches. A pair of diverticula arise from the fifth branchial pouch
and form what are termed the ultimo-branchial
bodies these fuse with the thyroid gland, but probably contribute no true
thyroid tissue.
Structure.—Microscopically
the parathyroids consist of intercommunicating columns of cells supported by
connective tissue containing a rich supply of blood capillaries. Most of the
cells are clear, but some, larger in size, contain oxyphil granules. Vesicles
containing colloid have been described as occurring in the parathyroid, but the
observation has not been confirmed.
No
doubt the parathyroid glands produce an internal secretion essential to the
well-being of the human economy; but it is still a matter of dispute what
symptoms of disease are produced by their removal and suppression of their
secretion. Pepere believes that they show signs of exceptional activity during
pregnancy, and that parathyroid insufficiency is a main factor in the
production of tetany in infants and adults, of eclampsia, and of certain sorts
of fits. It is probable that the tetany following parathyroidectomy is due to
the accumulation of ammonium carbonate and
The
Thymus is a temporary organ,
attaining its largest size at the time of puberty (Hammar), when it ceases to
grow, gradually dwindles, and almost disappears. If examined when its growth is
most active, it will be found to consist of two lateral lobes placed in close
contact along the middle line, situated partly in the thorax, partly in the neck,
and extending from the fourth costal cartilage upward, as high as the lower
border of the thyroid gland. It is covered by the sternum, and by the origins
of the Sternohyoidei and Sternothyreoidei. Below, it rests upon the
pericardium, being separated from the aortic arch and great vessels by a layer
of fascia. In the neck it lies on the front and sides of the trachea, behind
the Sternohyoidei and Sternothyreoidei. The two lobes generally differ in size;
they are occasionally united, so as to form a single mass; and sometimes
separated by an intermediate lobe. The thymus is of a pinkish-gray color, soft,
and lobulated on its surfaces. It is about
Development.—The
thymus appears in the form of two flask-shaped entodermal diverticula, which
arise, one on either side, from the third branchial pouch and extend
lateralward and backward into the surrounding mesoderm in front of the ventral
aortæ. Here they meet and become joined to one another by connective
tissue, but there is never any fusion of the thymus tissue proper. The
pharyngeal opening of each diverticulum is soon obliterated, but the neck of
the flask persists for some time as a cellular cord. By further proliferation
of the cells lining the flask, buds of cells are formed, which become
surrounded and isolated by the invading mesoderm. In the latter, numerous
lymphoid cells make their appearance, and are agregated to form lymphoid
follicles. These lymphoid cells are probably derivatives of the entodermal
cells which lined the original diverticula and their subdivisions. Additional
portions of thymus tissue are sometimes developed from the fourth branchial
pouches. Thymus continues to grow until the time of puberty and then begins to
atrophy.
Structure.—Each
lateral lobe is composed of numerous lobules held together by delicate areolar
tissue; the entire gland being enclosed in an investing capsule of a similar
but denser structure. The primary lobules vary in size from that of a pin’s
head to that of a small pea, and are made up of a number of small nodules or
follicles, which are irregular in shape and are more or less fused together,
especially toward the interior of the gland. Each follicle is from 1 to
Each
follicle is surrounded by a vascular plexus, from which vessels pass into the
interior, and radiate from the periphery toward the center, forming a second
zone just within the margin of the medullary portion. In the center of the
medullary portion there are very few vessels, and they are of minute size.
Watney
has made the important observation that hemoglobin is found in the thymus,
either in cysts or in cells situated near to, or forming part of, the
concentric corpuscles. This hemo globin occurs as granules or as circular
masses exactly resembling colored blood corpuscles. He has also discovered, in
the lymph issuing from the thymus, similar cells to those found in the gland,
and, like them, containing hemoglobin in the form of either granules or masses.
From these facts he arrives at the conclusion that the gland is one source of
the colored blood corpuscles. More recently Schaffer has observed actual
nucleated red-blood corpuscles in the thymus. The function of the thymus is
obscure. It seems to furnish during the period of growth an internal secretion
concerned with some phases of body metabolism, especially that of the sexual
glands.
Vessels and Nerves.—The
arteries supplying the thymus are
derived from the internal mammary, and from the superior and inferior thyroids.
The veins end in the left innominate
vein, and in the thyroid veins. The lymphatics
are described on page 698. The nerves
are exceedingly minute; they are derived from the vagi and sympathetic. Branches
from the descendens hypoglossi and phrenic reach the investing capsule, but do
not penetrate into the substance of the gland.
|
4d. The Hypophysis
Cerebri |
|
|
The
hypophysis (pituitary body) is a small reddish-gray body, about
The
hypophysis consists of an anterior and a posterior lobe, which differ from one
another in their mode of development and in their structure. The anterior lobe is the larger and is
somewhat kidney-shaped, the concavity being directed backward and embracing the
posterior lobe. It consists of a pars anterior and a pars intermedia, separated
from each other by a narrow cleft, the remnant of the pouch or diverticulum.
The pars anterior is extremely vascular and consists of epithelial cells of
varying size and shape, arranged in cord-like trabeculæ or alveoli and
separated by large, thin-walled bloodvessels. The pars intermedia is a thin
lamina closely applied to the body and neck of the posterior lobe and extending
onto the neighboring parts of the brain; it contains few bloodvessels and
consists of finely granular cells between which are small masses of colloid
material. The pars intermedia in spite of the fact that it arises in common
with the pars anterior from the ectoderm of the primitive buccal cavity is
often considered as a part of the posterior lobe which arises from the floor of
the third ventricle of the brain. Although of nervous origin the posterior lobe
contains no nerve cells or fibers. It consists of neuroglia cells and fibers
and is invaded by columns which grow into it from the pars intermedia; imbedded
in it are large quantities of a colloid substance histologically similar to
that found in the thyroid gland. In certain of the lower vertebrates, e.g., fishes, nervous structures are
present, and the lobe is of large size.
From
the pars intermedia a substance, no doubt an internal secretion, causes
constriction of the bloodvessels with rise of arterial blood-pressure. This
substance seems to have a stimulating effect on most of the smooth muscles,
acting directly upon the muscle causing contraction. It also increases the
secretion of the urine; of the mammary glands when in functional activity; and
of the cerebrospinal fluid. Extracts of this lobe also influence the general
metabolism of the carbohydrates by accelerating the process of glycogenolysis
in the liver.
The
pars anterior exercises a stimulating effect on the growth of the skeleton and
probably on connective tissues in general.
Enlargement
of the hypophysis and of the cavity of the sella turcica are found in the rare
disease acromegaly, which is
characterized by gradual enlargement of the face, hands, and feet, with
headache and often a peculiar type of blindness. This blindness is due to the
pressure of the enlarging hypophysis on the optic chiasma.
Development of the Hypophysis
Cerebri.—This in the adult consists of a large anterior,
consisting of the pars anterior and the pars intermedia, and a small posterior
lobe: the former is derived from the ectoderm of the stomodeum, the latter from
the floor of the fore-brain. About the fourth week there appears a pouchlike
diverticulum of the ectodermal lining of the roof of the stomodeum. This
diverticulum, pouch of Rathke, is the
rudiment of the anterior lobe of the hypophysis; it extends upward in front of
the cephalic end of the notochord and the remnant of the buccopharyngeal
membrane, and comes into contact with the under surface of the fore-brain. It
is then constricted off to form a closed vesicle, but remains for a time
connected to the ectoderm of the stomodeum by a solid cord of cells. Masses of
epithelial cells form on either side and in the front wall of the vesicle, and
by the growth between these of a stroma from the mesoderm the development of
the anterior lobe is completed. The upwardly directed hypophyseal involution
becomes applied to the antero-lateral aspect of a downwardly directed
diverticulum from the base of the fore-brain. This diverticulum constitutes the
future infundibulum in the floor of the third ventricle while its inferior
extremity becomes modified to form the posterior lobe of the hypophysis. In
some of the lower animals the posterior lobe contains nerve cells and nerve
fibers, but in man and the higher vertebrates these are replaced by connective
tissue. A canal, craniopharyngeal canal,
is sometimes found extending from the anterior part of the fossa hypophyseos of
the sphenoid bone to the under surface of the skull, and marks the original
position of Rathke’s pouch; while at the junction of the septum of the nose
with the palate traces of the stomodeal end are occasionally present (Frazer).
|
4e. The Pineal Body |
The
pineal body (epiphysis) is a small reddish-gray body, about
In
early life it has a glandular structure which reaches its greatest development
at about the seventh year. Later, especially after puberty, the glandular
tissue gradually disappears and is replaced by connective tissue.
Structure.—The
pineal body is destitute of nervous substance, and consists of follicles lined
by epithelium and enveloped by connective tissue. These follicles contain a
variable quantity of gritty material, composed of phosphate and carbonate of
calcium, phosphate of magnesium and ammonia, and a little animal matter.
It
contains a substance which if injected intravenously causes fall of
blood-pressure. It seems probable that the gland furnishes an internal
secretion in children that inhibits the development of the reproductive glands
since the invasion of the gland in children, by pathological growths which
practically destroy the glandular tissue, results in accelerated development of
the sexual organs, increased growth of the skeleton and precocious mentality.
|
|
Chromaphil
or chromaffin cells, so-called because they stain yellow or brownish with
chromium salts, are associated with the ganglia of the sympathetic nervous
system.
Development.—They
arise in common with the sympathetic cells from the neural crest, and are
therefore ectodermal in origin. The chromaphil and sympathetic cells are
indistinguishable from one another at the time of their migration from the
spinal ganglia to the regions occupied in the adult. Differentiation of
chromaphil cells begins in embryos about
The
paraganglia are small groups of
chromaphil cells connected with the ganglia of the sympathetic trunk and the
ganglia of the celiac, renal, suprarenal, aortic and hypogastric plexuses. They
are sometimes found in connection with the ganglia of other sympathetic
plexuses. None have been found with the sympathetic ganglia associated with the
branches of the trigeminal nerve.
The
aortic glands or bodies are the largest of these groups
of chromaphil cells and measure in the newborn about
The
medullary portions of the suprarenal glands and the glomus caroticum belong to
the chromaphil system.
the Suprarenal Glands (Glandulæ
Suprarenalis; Adrenal Capsule) are two small flattened
bodies of a yellowish color, situated at the back part of the abdomen, behind
the peritoneum, and immediately above and in front of the upper end of each
kidney; hence their name. The right one is somewhat triangular in shape,
bearing a resemblance to a cocked hat; the left is more semilunar, usually
larger, and placed at a higher level than the right. They vary in size in
different individuals, being sometimes so small as to be scarcely detected:
their usual size is from 3 to
Development.—Each
suprarenal gland consists of a cortical portion derived from the celomic
epithelium and a medullary portion originally composed of sympatho-chromaffin
tissue. The cortical portion is first recognizable about the beginning of the
fourth week as a series of buds from the celomic cells at the root of the
mesentery. Later it becomes completely separated from the celomic epithelium
and forms a suprarenal ridge projecting into the celom between the mesonephros
and the root of the mesentery. Into this cortical portion cells from the
neighboring masses of sympatho-chromaffin tissue migrate along the line of its
central vein to reach and form the medullary portion of the gland.
Relations.—The
relations of the suprarenal glands differ on the two sides of the body.
The
right suprarenal is situated behind
the inferior vena cava and right lobe of the liver, and in front of the
diaphragm and upper end of the right kidney. It is roughly triangular in shape;
its base, directed downward, is in contact with the medial and anterior aspects
of the upper end of the right kidney. It presents two surfaces for examination,
an anterior and a posterior. The anterior
surface looks forward and lateralward, and has two areas: a medial, narrow,
and non-peritoneal, which lies behind the inferior vena cava; and a lateral,
somewhat triangular, in contact with the liver. The upper part of the latter
surface is devoid of peritoneum, and is in relation with the bare area of the liver
near its lower and medial angle, while its inferior portion is covered by
peritoneum, reflected onto it from the inferior layer of the coronary ligament;
occasionally the duodenum overlaps the inferior portion. A little below the
apex, and near the anterior border of the gland, is a short furrow termed the hilum, from which the suprarenal vein
emerges to join the inferior vena cava. The posterior
surface is divided into upper and lower parts by a curved ridge: the upper,
slightly convex, rests upon the diaphragm; the lower, concave, is in contact
with the upper end and the adjacent part of the anterior surface of the kidney.
The
left suprarenal, slightly larger
than the right, is crescentic in shape, its concavity being adapted to the
medial border of the upper part of the left kidney. It presents a medial
border, which is convex, and a lateral, which is concave; its upper end is
narrow, and its lower rounded. Its anterior
surface has two areas: an upper one, covered by the peritoneum of the
omental bursa, which separates it from the cardiac end of the stomach, and
sometimes from the superior extremity of the spleen; and a lower one, which is
in contact with the pancreas and lienal artery, and is therefore not covered by
the peritoneum. On the anterior surface, near its lower end, is a furrow or
hilum, directed downward and forward, from which the suprarenal vein emerges.
Its posterior surface presents a
vertical ridge, which divides it into two areas; the lateral area rests on the
kidney, the medial and smaller on the left crus of the diaphragm.
The
surface of the suprarenal gland is surrounded by areolar tissue containing much
fat, and closely invested by a thin fibrous capsule, which is difficult to
remove on account of the numerous fibrous processes and vessels entering the
organ through the furrows on its anterior surface and base.
Small
accessory suprarenals (glandulæ suprarenales accessoriæ)
are often to be found in the connective tissue around the suprarenals. The
smaller of these, on section, show a uniform surface, but in some of the larger
a distinct medulla can be made out.
Structure.—On
section, the suprarenal gland is seen to consist of two portions: an external or cortical and an internal
or medullary. The former constitutes
the chief part of the organ, and is of a deep yellow color; the medullary
substance is soft, pulpy, and of a dark red or brown color.
The
cortical portion (substantia corticalis) consists of a
fine connective-tissue net-work, in which is imbedded the glandular epithelium.
The epithelial cells are polyhedral in shape and possess rounded nuclei; many
of the cells contain coarse granules, others lipoid globules. Owing to
differences in the arrangement of the cells, three distinct zones can be made
out: (1) the zona glomerulosa,
situated beneath the capsule, consists of cells arranged in rounded groups,
with here and there indications of an alveolar structure; the cells of this
zone are very granular, and stain deeply. (2) The zona fasciculata, continuous with the zona glomerulosa, is composed
of columns of cells arranged in a radial manner; these cells contain finer
granules and in many instances globules of lipoid material. (3) The zona reticularis, in contact with the
medulla, consists of cylindrical masses of cells irregularly arranged; these
cells often contain pigment granules which give this zone a darker appearance
than the rest of the cortex.
The
medullary portion (substantia medullaris) is extremely
vascular, and consists of large chromaphil cells arranged in a network. The
irregular polyhedral cells have a finely granular cystoplasm that are probably
concerned with the secretion of adrenalin. In the meshes of the cellular
network are large anastomosing venous sinuses (sinusoids) which are in close
relationship with the chromaphil or medullary cells. In many places the
endothelial lining of the blood sinuses is in direct contact with the medullary
cells. Some authors consider the endothelium absent in places and here the
medullary cells are directly bathed by the blood. This intimate relationship
between the chromaphil cells and the blood stream undoubtedly facilitates the
discharge of the internal secretion into the blood. There is a loose meshwork
of supporting connective tissue containing non-striped muscle fibers. This
portion of the gland is richly supplied with non-medullated nerve fibers, and
here and there sympathetic ganglia are found.
Vessels and Nerves.—The
arteries supplying the suprarenal
glands are numerous and of comparatively large size; they are derived from the
aorta, the inferior phrenic, and the renal. They subdivide into minute branches
previous to entering the cortical part of the gland, where they break up into
capillaries which end in the venous plexus of the medullary portion.
The
suprarenal vein returns the blood
from the medullary venous plexus and receives several branches from the
cortical substance; it emerges from the hilum of the gland and on the right
side opens into the inferior vena cava, on the left into the renal vein.
The
lymphatics end in the lumbar glands.
The
nerves are exceedingly numerous, and
are derived from the celiac and renal plexuses, and, according to Bergmann,
from the phrenic and vagus nerves. They enter the lower and medial part of the
capsule, traverse the cortex, and end around the cells of the medulla. They
have numerous small ganglia developed upon them in the medullary portion of the
gland.
In
connection with the development of the medulla from the sympathochromaffin
tissue, it is to be noted that this portion of the gland secretes a substance, adrenalin, which has a powerful
influence on those muscular tissues which are supplied by sympathetic fibers.
Glomus Caroticum (Carotid Glands;
Carotid Bodies)—The carotid
bodies, two in number, are situated one on either side of the neck, behind
the common carotid artery at its point of bifurcation into the external and
internal carotid trunks. They are reddish brown in color and oval in shape, the
long diameter measuring about
Each
is invested by a fibrous capsule and consists largely of spherical or irregular
masses of cells, the masses being more or less
isolated from one another by septa which extend inward from the deep surface of
the capsule. The cells are polyhedral in shape, and each contains a large nucleus
imbedded in finely granular protoplasm, which is stained yellow by chromic
salts. Numerous nerve fibers, derived from the sympathetic plexus on the
carotid artery, are distributed throughout the organ, and a net-work of large
sinusoidal capillaries ramifies among the cells.
Glomus Coccygeum (Coccygeal Gland or
Body; Luschka’s Gland)—The glomus coccygeum is placed in front of, or immediately below, the
tip of the coccyx. It is about
It
consists of irregular masses of round or polyhedral cells, the cells of each
mass being grouped around a dilated sinusoidal capillary vessel. Each cell
contains a large round or oval nucleus, the protoplasm surrounding which is
clear, and is not stained by chromic salts.