Skull as A whole.
Cranial BASE and calvaria. BONY
PALATE. TEMPORAL, INFRATEMPORAL, PTERYGOPA-LATINE
FOSSAE.
Orbit. Nasal cavity
Lesson # 4
Theme 1.
Skull as whole.
Cranial BASE and calvaria. BONY
PALATE. TEMPORAL, INFRATEMPORAL, PTERYGOPALA-TINE FOSSAE
Pterygopalatine fossa formed
anteriorly by maxillary body, posteriorly by base of pterygoid
process of the sphenoid bone and medially - by the perpendicular plate of the
palatine bone. Prygopalatine fossa communicates with
internal cranial base through foramen rotundum, with
orbit thruogh inferior orbital fissura,
with mouth cavity through greater and lesser palatine canals, with external
cranial base (foramen lacerum) through pterygoid canal.
The Pterygopalatine Fossa (fossa pterygopalatina; sphenomaxillary
fossa).—The pterygopalatine
fossa is a small, triangular space at the angle of junction of the inferior
orbital and pterygomaxillary fissures, and placed
beneath the apex of the orbit. It is bounded above by the under surface
of the body of the sphenoid and by the orbital process of the palatine bone; in
front, by the infratemporal surface of the
maxilla; behind, by the base of the pterygoid
process and lower part of the anterior surface of the great wing of the
sphenoid; medially, by the vertical part of the palatine bone with its
orbital and sphenoidal processes.
This fossa communicates with the orbit by the inferior orbital fissure,
with the nasal cavity by the sphenopalatine foramen,
and with the infratemporal fossa by the pterygomaxillary fissure. Five foramina open into it. Of
these, three are on the posterior wall, viz., the foramen rotundum, the pterygoid
canal, and the pharyngeal canal, in this order downward and medialward. On the medial wall is the sphenopalatine
foramen, and below is the superior orifice of the pterygopalatine
canal. The fossa contains the maxillary nerve, the sphenopalatine
ganglion, and the terminal part of the internal maxillary artery.
The skull is the skeleton of the head,
a series of bones from its two parts, the Neurocranium
and Facial skull. The neurocranium provides a case
for the brain and cranial meninges, proximal parts of the cranial nerves, and
blood vessels.
The term cranium (means skull) is sometimes restricted to a skull
without the mandible. The cranium has a domelike root – the Calvaria
– skullcap – and a floor or cranial base consisting of the ethmoid
bone and parts of the occipital and temporal bones. The facial skeleton
consists of the bones surrounding the mouth and nose and contributing to the
orbits (eye sockets, orbital cavities). In the anatomical position, the skull
is oriented so that the inferior margin of the orbit (eye socket) and the
superior margin of the external acustic meatus
(auditory canal) are horizontal.
The skull as a whole may be viewed from different points, and the views
so obtained are termed the normæ of the
skull; thus, it may be examined from above (norma verticalis),
from below (norma basalis),
from the side (norma lateralis),
from behind (norma occipitalis),
or from the front (norma frontalis).
Norma Verticalis.—When viewed from above the outline presented varies greatly
in different skulls; in some it is more or less oval, in others more nearly
circular. The surface is traversed by three sutures, viz.: (1) the coronal
sutures, nearly transverse is direction, between the frontal and parietals;
(2) the sagittal sutures, medially placed, between the parietal bones,
and deeply serrated in its anterior two-thirds; and (3) the upper part of the lambdoidal suture, between the parietals and
the occipital. The point of junction of the sagittal and coronal suture is
named the bregma, that of the sagittal
and lambdoid sutures, the lambda; they
indicate respectively the positions of the anterior and posterior fontanelles in the fetal skull.
On either side of the sagittal suture are the parietal eminence and parietal
foramen—the latter, however, is frequently absent on one or both sides. The
skull is often somewhat flattened in the neighborhood
of the parietal foramina, and the term obelion
is applied to that point of the sagittal suture which is on a level with the
foramina. In front is the glabella, and on its lateral aspects are the superciliary arches, and above these the frontal
eminences. Immediately above the glabella may be seen the remains of the frontal
suture; in a small percentage of skulls this suture persists and extends
along the middle line to the bregma. Passing backward
and upward from the zygomatic processes of the
frontal bone are the temporal lines, which mark the upper limits of the
temporal fossæ. The zygomatic
arches may or may not be seen projecting beyond the anterior portions of these
lines.
Base of skull. Inferior surface.
Norma Basalis—The
inferior surface of the base of the skull, exclusive of the mandible, is
bounded in front by the incisor teeth in the maxillæ;
behind, by the superior nuchal lines of the occipital; and laterally by the
alveolar arch, the lower border of the zygomatic
bone, the zygomatic arch and an imaginary line
extending from it to the mastoid process and extremity of the superior nuchal
line of the occipital. It is formed by the palatine processes of the maxillæ and palatine bones, the vomer,
the pterygoid processes, the under surfaces of the
great wings, spinous processes, and part of the body
of the sphenoid, the under surfaces of the squamæ
and mastoid and petrous portions of the temporals,
and the under surface of the occipital bone. The anterior part or hard palate
projects below the level of the rest of the surface, and is bounded in front
and laterally by the alveolar arch containing the sixteen teeth of the maxillæ. Immediately behind the incisor teeth is the incisive
foramen. In this foramen are two lateral apertures, the openings of the incisive
canals (foramina of Stenson) which
transmit the anterior branches of the descending palatine vessels, and the nasopalatine nerves. Occasionally two additional canals are
present in the incisive foramen; they are termed the foramina of Scarpa and are situated in the middle line; when
present they transmit the nasopalatine nerves. The
vault of the hard palate is concave, uneven, perforated by numerous foramina,
marked by depressions for the palatine glands, and traversed by a crucial
suture formed by the junction of the four bones of which it is composed. In the
young skull a suture may be seen extending on either side from the incisive
foramen to the interval between the lateral incisor and canine teeth, and
marking off the os incisivum
or premaxillary bone. At either posterior angle of
the hard palate is the greater palatine foramen, for the transmission of
the descending palatine vessels and anterior palatine nerve; and running
forward and medialward from it a groove, for the same
vessels and nerve. Behind the posterior palatine foramen is the pyramidal
process of the palatine bone, perforated by one or more lesser
palatine foramina, and marked by the commencement of a transverse ridge,
for the attachment of the tendinous expansion of the
Tensor veli palatini.
Projecting backward from the center of the posterior
border of the hard palate is the posterior nasal spine, for the
attachment of the Musculus uvulæ.
Behind and above the hard palate are the choanæ,
measuring about
Behind the nasal cavities is the basilar portion of the
occipital bone, presenting near its center the pharyngeal
tubercle for the attachment of the fibrous raphé
of the pharynx, with depressions on either side for the insertions of the
Rectus capitis anterior and Longus
capitis. At the base of the lateral pterygoid plate is the foramen ovale,
for the transmission of the mandibular nerve, the accessory meningeal artery,
and sometimes the lesser superficial petrosal nerve;
behind this are the foramen spinosum which
transmits the middle meningeal vessels, and the prominent spina
angularis (sphenoidal
spine), which gives attachment to the sphenomandibular
ligament and the Tensor veli palatini.
Lateral to the spina angularis
is the mandibular fossa, divided into two parts by the petrotympanic fissure; the anterior portion,
concave, smooth bounded in front by the articular tubercle, serves for
the articulation of the condyle of the mandible; the posterior portion, rough
and bounded behind by the tympanic part of the temporal, is sometimes occupied
by a part of the parotid gland. Emerging from between the laminæ
of the vaginal process of the tympanic part is the styloid
process; and at the base of this process is the stylomastoid
foramen, for the exit of the facial nerve, and entrance of the stylomastoid artery. Lateral to the stylomastoid
foramen, between the tympanic part and the mastoid process, is the tympanomastoid fissure, for the auricular
branch of the vagus. Upon the medial side of the
mastoid process is the mastoid notch for the posterior belly of the Digastricus, and medial to the notch, the occipital
groove for the occipital artery. At the base of the medial pterygoid plate is a large and somewhat triangular
aperture, the foramen lacerum, bounded in
front by the great wing of the sphenoid, behind by the apex of the petrous
portion of the temporal bone, and medially by the body of the sphenoid and
basilar portion of the occipital bone; it presents in front the posterior
orifice of the pterygoid canal; behind,
the aperture of the carotid canal. The lower part of this opening is
filled up in the fresh state by a fibrocartilaginous
plate, across the upper or cerebral surface of which the internal carotid
artery passes. Lateral to this aperture is a groove, the sulcus tubæ auditivæ,
between the petrous part of the temporal and the great wing of the sphenoid.
This sulcus is directed lateralward and backward from
the root of the medial pterygoid plate and lodges the
cartilaginous part of the auditory tube; it is continuous behind with the canal
in the temporal bone which forms the bony part of the same tube. At the bottom
of this sulcus is a narrow cleft, the petrosphenoidal
fissure, which is occupied, in the fresh condition, by a plate of
cartilage. Behind this fissure is the under surface of the petrous portion of
the temporal bone, presenting, near its apex, the quadrilateral rough surface,
part of which affords attachment to the Levator veli palatini; lateral to this
surface is the orifice of the carotid canal, and medial to it, the
depression leading to the aquæductus cochleæ, the former transmitting the internal
carotid artery and the carotid plexus of the sympathetic, the latter serving
for the passage of a vein from the cochlea. Behind the carotid canal is the jugular
foramen, a
large aperture, formed in front by the petrous portion of the temporal,
and behind by the occipital; it is generally
larger on the right than on the left side, and may be subdivided into three
compartments. The anterior compartment transmits the inferior petrosal sinus; the intermediate, the glossopharyngeal, vagus, and accessory nerves; the posterior, the transverse
sinus and some meningeal branches from the occipital and ascending pharyngeal
arteries. On the ridge of bone dividing the carotid canal from the jugular
foramen is the inferior tympanic canaliculus
for the transmission of the tympanic branch of the glossopharyngeal nerve; and
on the wall of the jugular foramen, near the root of the styloid
process, is the mastoid canaliculus for the
passage of the auricular branch of the vagus nerve.
Extending forward from the jugular foramen to the foramen lacerum
is the petrooccipital fissure occupied,
in the fresh state, by a plate of cartilage. Behind the basilar portion of the
occipital bone is the foramen magnum, bounded laterally by the occipital
condyles, the medial sides of which are rough for the attachment of the alar
ligaments. Lateral to each condyle is the jugular process which gives
attachment to the Rectus capitis lateralis
muscle and the lateral atlantooccipital ligament. The
foramen magnum transmits the medulla oblongata and its membranes, the accessory
nerves, the vertebral arteries, the anterior and posterior spinal arteries, and
the ligaments connecting the occipital bone with the axis. The mid-points on
the anterior and posterior margins of the foramen magnum are respectively
termed the basion and the opisthion.
In front of each condyle is the canal for the passage of the hypoglossal nerve
and a meningeal artery. Behind each condyle is the condyloid
fossa, perforated on one or both sides by the condyloid
canal, for the transmission of a vein from the transverse sinus. Behind the
foramen magnum is the median nuchal line ending above at the external
occipital protuberance, while on either side are the superior and inferior
nuchal lines; these, as well as the surfaces of bone between them, are
rough for the attachment of the muscles which are enumerated on pages.
Side view of the skull.
Norma Lateralis—When
viewed from the side the skull is seen to consist of the cranium above and
behind, and of the face below and in front. The cranium is somewhat ovoid in
shape, but its contour varies in different cases and depends largely on the
length and height of the skull and on the degree of prominence of the superciliary arches and frontal eminences. Entering into
its formation are the frontal, the parietal, the occipital, the temporal, and
the great wing of the sphenoid. These bones are joined to one another and to
the zygomatic by the following sutures: the zygomaticotemporal between the zygomatic
process of the temporal and the temporal process of the zygomatic;
the zygomaticofrontal uniting the zygomatic bone with the zygomatic
process of the frontal; the sutures surrounding the great wing of the sphenoid,
viz., the sphenozygomatic in front, the sphenofrontal and sphenoparietal
above, and the sphenosquamosal behind. The sphenoparietal suture varies in length in different skulls,
and is absent in those cases where the frontal articulates with the temporal squama. The point corresponding with the posterior end of
the sphenoparietal suture is named the pterion;
it is situated about
The squamosal suture arches backward from the pterion
and connects the temporal squama with the lower
border of the parietal: this suture is continuous behind with the short, nearly
horizontal parietomastoid suture, which
unites the mastoid process of the temporal with the region of the mastoid angle
of the parietal. Extending from above downward and forward across the cranium
are the coronal and lambdoidal
sutures; the former connects the parietals with the frontal, the latter,
the parietals with the occipital. The lambdoidal
suture is continuous below with the occipitomastoid
suture between the occipital and the mastoid portion of the temporal. In or
near the last suture is the mastoid foramen, for the transmission of an
emissary vein. The point of meeting of the parietomastoid,
occipitomastoid, and lambdoidal
sutures is known as the asterion.
Immediately above the orbital margin is the superciliary
arch, and, at a higher level, the frontal eminence. Near the center of the parietal bone is the parietal eminence.
Posteriorly is the external occipital protuberance, from which the
superior nuchal line may be followed forward to the mastoid process. Arching
across the side of the cranium are the temporal lines, which mark the
upper limit of the temporal fossa.
Temporal fossa formed by frontal squama and parietal bone. It bordered superiorly by
temporal line, inferiorly – infratemporal srest and zygomatic arch.
Temporal fossa contains temporal muscle.
Infratemporal fossa
bordered by tuber maxillae, superiorly - infratemporal
srest, medially it contimues
into pterygopalatine fossa. Anteriorly infraemporal fossa communicates with orbit through inferior
orbital fissura.
The Temporal Fossa (fossa temporalis).—The temporal fossa is bounded above and behind by the temporal lines,
which extend from the zygomatic process of the
frontal bone upward and backward across the frontal and parietal bones, and
then curve downward and forward to become continuous with the supramastoid crest and the posterior root of the zygomatic arch. The point where the upper temporal line
cuts the coronal suture is named the stephanion.
The temporal fossa is bounded in front by the frontal and zygomatic bones, and opening on the back of the latter is
the zygomaticotemporal foramen. Laterally
the fossa is limited by the zygomatic arch, formed by
the zygomatic and temporal bones; below, it is
separated from the infratemporal fossa by the infratemporal crest on the great wing of the
sphenoid, and by a ridge, continuous with this crest, which is carried backward
across the temporal squama to the anterior root of
the zygomatic process. In front and below, the fossa
communicates with the orbital cavity through the inferior orbital or sphenomaxillary fissure. The floor of the
fossa is deeply concave in front and convex behind, and is formed by the zygomatic, frontal, parietal, sphenoid, and temporal bones.
It is traversed by vascular furrows; one, usually well-marked, runs upward
above and in front of the external acoustic meatus, and lodges the middle
temporal artery. Two others, frequently indistinct, may be observed on the
anterior part of the floor, and are for the anterior and posterior deep
temporal arteries. The temporal fossa contains the Temporalis muscle and its
vessels and nerves, together with the zygomaticotemporal
nerve.
The zygomatic arch
is formed by the zygomatic process of the temporal
and the temporal process of the zygomatic, the two
being united by an oblique suture; the tendon of the Temporalis passes medial
to the arch to gain insertion into the coronoid process of the mandible. The zygomatic process of the temporal arises by two roots, an
anterior, directed inward in front of the mandibular fossa, where it expands to
form the articular tubercle, and a posterior, which runs backward above the
external acoustic meatus and is continuous with the supramastoid
crest. The upper border of the arch gives attachment to the temporal fascia;
the lower border and medial surface give origin to the Masseter.
Below the posterior root of the zygomatic
arch is the elliptical orifice of the external acoustic meatus, bounded
in front, below, and behind by the tympanic part of the temporal bone; to its
outer margin the cartilaginous segment of the external acoustic meatus is
attached. The small triangular area between the posterior root of the zygomatic arch and the postero-superior
part of the orifice is termed the suprameatal
triangle, on the anterior border of which a small spinous
process, the suprameatal spine, is
sometimes seen. Between the tympanic part and the articular tubercle is the mandibular
fossa, divided into two parts by the petrotympanic
fissure. The anterior and larger part of the fossa articulates with the condyle
of the mandible and is limited behind by the external acoustic meatus: the
posterior part sometimes lodges a portion of the parotid gland. The styloid process extends downward and forward for a variable
distance from the lower part of the tympanic part, and gives attachment to the Styloglossus, Stylohyoideus, and Stylopharyngeus, and to the stylohyoid
and stylomandibular ligaments. Projecting downward
behind the external acoustic meatus is the mastoid process, to the outer
surface of which the Sternocleidomastoideus, Splenius
capitis, and Longissimus capitis are attached.
Left infratemporal
fossa.
The Infratemporal Fossa (fossa infratemporalis; zygomatic fossa)—The infratemporal fossa is an irregularly
shaped cavity, situated below and medial to the zygomatic
arch. It is bounded, in front, by the infratemporal
surface of the maxilla and the ridge which descends from its zygomatic process; behind, by the articular tubercle
of the temporal and the spinal angularis of the
sphenoid; above, by the great wing of the sphenoid below the infratemporal crest, and by the under surface of the
temporal squama; below, by the alveolar border
of the maxilla; medially, by the lateral pterygoid
plate. It contains the lower part of the Temporalis, the Pterygoidei
internus and externus, the
internal maxillary vessels, and the mandibular and maxillary nerves. The foramen
ovale and foramen spinosum
open on its roof, and the alveolar canals on its anterior wall. At its
upper and medial part are two fissures, which together form a T-shaped fissure,
the horizontal limb being named the inferior orbital, and the vertical one the pterygomaxillary.
The inferior orbital fissure (fissura
orbitalis inferior; sphenomaxillary
fissure), horizontal in direction, opens into the lateral and back part of
the orbit. It is bounded above by the lower border of the orbital
surface of the great wing of the sphenoid; below, by the lateral border
of the orbital surface of the maxilla and the orbital process of the palatine
bone; laterally, by a small part of the zygomatic
bone: 48
medially, it joins at right
angles with the pterygomaxillary fissure. Through the
inferior orbital fissure the orbit communicates with the temporal, infratemporal, and pterygopalatine
fossæ; the fissure transmits the maxillary
nerve and its zygomatic branch, the infraorbital vessels, the ascending branches from the sphenopalatine ganglion, and a vein which connects the
inferior ophthalmic vein with the pterygoid venous
plexus.
The pterygomaxillary
fissure is vertical, and descends at right angles from the medial end of
the preceding; it is a triangular interval, formed by the divergence of the
maxilla from the pterygoid process of the sphenoid.
It connects the infratemporal with the pterygopalatine fossa, and transmits the terminal part of
the internal maxillary artery.
Norma Occipitalis.—When
viewed from behind the cranium presents a more or less circular outline. In the
middle line is the posterior part of the sagittal suture connecting the
parietal bones; extending downward and lateralward
from the hinder end of the sagittal suture is the deeply serrated lambdoidal suture joining the parietals to
the occipital and continuous below with the parietomastoid
and occipitomastoid sutures; it
frequently contains one or more sutural bones. Near
the middle of the occipital squama is the external
occipital protuberance or inion, and extending lateralward
from it on either side is the superior nuchal line, and above this the faintly
marked highest nuchal line. The part of the squama
above the inion and highest lines is named the planum
occipitale, and is covered by the Occipitalis muscle; the part below is termed the planum nuchale, and
is divided by the median nuchal line which runs downward and forward from the
inion to the foramen magnum; this ridge gives attachment to the ligamentum nuchæ. The
muscles attached to the planum nuchale
are enumerated on p. 130. Below and in front are the mastoid processes, convex
laterally and grooved medially by the mastoid notches. In or near the occipitomastoid suture is the mastoid foramen for
the passage of the mastoid emissary vein.
Norma Frontalis—When
viewed from the front the skull exhibits a somewhat oval outline, limited above
by the frontal bone, below by the body of the mandible, and laterally
by the zygomatic bones and the mandibular rami. The
upper part, formed by the frontal squama, is smooth
and convex. The lower part, made up of the bones of the face, is irregular; it
is excavated laterally by the orbital cavities, and presents in the middle line
the anterior nasal aperture leading to the nasal cavities, and below
this the transverse slit between the upper and lower dental arcades.
The skull from the front.
Above,
the frontal eminences stand out more or less prominently, and beneath
these are the superciliary arches,
joined to one another in the middle by the glabella. On and above the
glabella a trace of the frontal suture sometimes persists; beneath it is
the frontonasal suture, the mid-point of which is
termed the nasion. Behind and below the
frontonasal suture the frontal articulates with the
frontal process of the maxilla and with the lacrimal. Arching transversely
below the superciliary arches is the upper part of
the margin of the orbit, thin and prominent in its lateral two-thirds, rounded
in its medial third, and presenting, at the junction of these two portions, the
supraorbital notch or foramen for the supraorbital nerve and
vessels. The supraorbital margin ends laterally in the zygomatic
process which articulates with the zygomatic bone,
and from it the temporal line extends upward and backward. Below the frontonasal suture is the bridge of the nose, convex from
side to side, concavo-convex from above downward, and formed by the two nasal
bones supported in the middle line by the perpendicular plate of the ethmoid, and laterally by the frontal processes of the maxillæ which are prolonged upward between the nasal
and lacrimal bones and form the lower and medial part of the circumference of
each orbit. Below the nasal bones and between the maxillæ
is the anterior aperture of the nose, pyriform in
shape, with the narrow end directed upward. Laterally this opening is bounded
by sharp margins, to which the lateral and alar cartilages of the nose are
attached; below, the margins are thicker and curve medialward
and forward to end in the anterior nasal spine. On looking into the
nasal cavity, the bony septum which separates the nasal cavities presents, in
front, a large triangular deficiency; this, in the fresh state, is filled up by
the cartilage of the nasal septum; on the lateral wall of each nasal cavity the
anterior part of the inferior nasal concha is visible. Below and lateral to the
anterior nasal aperture are the anterior surfaces of the maxillæ,
each perforated, near the lower margin of the orbit, by the infraorbital
foramen for the passage of the infraorbital nerve
and vessels. Below and medial to this foramen is the canine eminence separating
the incisive from the canine fossa. Beneath these fossæ
are the alveolar processes of the maxillæ
containing the upper teeth, which overlap the teeth of the mandible in front.
The zygomatic bone on either side forms the
prominence of the cheek, the lower and lateral portion of the orbital cavity,
and the anterior part of the zygomatic arch. It
articulates medially with the maxilla, behind with the zygomatic
process of the temporal, and above with the great wing of the sphenoid and the zygomatic process of the frontal; it is perforated by the zygomaticofacial foramen for the passage of
the zygomaticofacial nerve. On the body of the
mandible is a median ridge, indicating the position of the symphysis;
this ridge divides below to enclose the mental protuberance, the lateral angles
of which constitute the mental tubercles. Below the incisor teeth is the incisive
fossa, and beneath the second premolar tooth the mental foramen
which transmits the mental nerve and vessels. The oblique line runs upward from
the mental tubercle and is continuous behind with the anterior border of the
ramus. The posterior border of the ramus runs downward and forward from the
condyle to the angle, which is frequently more or less everted.
The Interior of the Skull
Inner Surface of the Skull-cap.—The
inner surface of the skull-cap is concave and presents depressions for the
convolutions of the cerebrum, together with numerous furrows for the lodgement
of branches of the meningeal vessels. Along the middle line is a longitudinal
groove, narrow in front, where it commences at the frontal crest, but broader
behind; it lodges the superior sagittal sinus, and its margins afford
attachment to the falx cerebri.
On either side of it are several depressions for the arachnoid granulations,
and at its back part, the openings of the parietal foramina when these
are present. It is crossed, in front, by the coronal suture, and behind
by the lambdoidal, while the sagittal
lies in the medial plane between the parietal bones.
Upper Surface of the Base of the Skull—The
upper surface of the base of the skull or floor of the cranial cavity presents
three fossæ, called the anterior, middle,
and posterior cranial fossæ.
Anterior Fossa (fossa cranii anterior).—The floor of the anterior fossa is formed by the orbital plates of the
frontal, the cribriform plate of the ethmoid, and the
small wings and front part of the body of the sphenoid; it is limited behind by
the posterior borders of the small wings of the sphenoid and by the anterior
margin of the chiasmatic groove. It is traversed by
the frontoethmoidal, sphenoethmoidal,
and sphenofrontal sutures. Its lateral
portions roof in the orbital cavities and support the frontal lobes of the
cerebrum; they are convex and marked by depressions for the brain convolutions,
and grooves for branches of the meningeal vessels. The central portion
corresponds with the roof of the nasal cavity, and is markedly depressed on
either side of the crista galli. It presents, in and
near the median line, from before backward, the commencement of the frontal
crest for the attachment of the falx cerebri; the foramen cecum, between the frontal bone
and the crista galli of the ethmoid,
which usually transmits a small vein from the nasal cavity to the superior
sagittal sinus; behind the foramen cecum, the crista galli,
the free margin of which affords attachment to the falx
cerebri; on either side of the crista galli, the olfactory groove formed by the cribriform
plate, which supports the olfactory bulb and presents foramina for the
transmission of the olfactory nerves, and in front a slit-like opening for the nasociliary nerve. Lateral to either olfactory groove are
the internal openings of the anterior and posterior ethmoidal foramina; the anterior, situated about the
middle of the lateral margin of the olfactory groove, transmits the anterior ethmoidal vessels and the nasociliary
nerve; the nerve runs in a groove along the lateral edge of the cribriform
plate to the slit-like opening above mentioned; the posterior ethmoidal foramen opens at the back part of this margin
under cover of the projecting lamina of the sphenoid, and transmits the
posterior ethmoidal vessels and nerve. Farther back
in the middle line is the ethmoidal spine,
bounded behind by a slight elevation separating two shallow longitudinal
grooves which support the olfactory lobes. Behind this is the anterior margin
of the chiasmatic groove, running lateralward
on either side to the upper margin of the optic foramen.
The Middle Fossa (fossa cranii media).—The middle fossa, deeper than the preceding, is narrow in the middle,
and wide at the sides of the skull. It is bounded in front by the
posterior margins of the small wings of the sphenoid, the anterior clinoid processes, and the ridge forming the anterior
margin of the chiasmatic groove; behind, by
the superior angles of the petrous portions of the temporals
and the dorsum sellæ; laterally by the
temporal squamæ, sphenoidal
angles of the parietals, and great wings of the sphenoid. It is traversed by
the squamosal, sphenoparietal, sphenosquamosal,
and sphenopetrosal sutures.
The middle part of the fossa presents, in front, the chiasmatic groove and tuberculum
sellæ; the chiasmatic
groove ends on either side at the optic foramen, which transmits the
optic nerve and ophthalmic artery to the orbital cavity. Behind the optic
foramen the anterior clinoid process is
directed backward and medialward and gives attachment
to the tentorium cerebelli. Behind the tuberculum sellæ is a deep
depression, the sella turcica,
containing the fossa hypophyseos, which lodges
the hypophysis, and presents on its anterior wall the
middle clinoid processes. The sella turcica is bounded
posteriorly by a quadrilateral plate of bone, the dorsum sellæ,
the upper angles of which are surmounted by the posterior clinoid processes: these afford attachment to the
tentorium cerebelli, and below each is a notch for
the abducent nerve. On either side of the sella turcica is the carotid
groove, which is broad, shallow, and curved somewhat like the italic letter
f. It begins behind at the foramen lacerum,
and ends on the medial side of the anterior clinoid
process, where it is sometimes converted into a foramen (carotico-clinoid)
by the union of the anterior with the middle clinoid
process; posteriorly, it is bounded laterally by the lingula.
This groove lodges the cavernous sinus and the internal carotid artery, the
latter being surrounded by a plexus of sympathetic nerves.
Base of the skull. Upper surface.
The lateral parts of the middle fossa are of considerable
depth, and support the temporal lobes of the brain. They are marked by depressions
for the brain convolutions and traversed by furrows for the anterior and
posterior branches of the middle meningeal vessels. These furrows begin near
the foramen spinosum, and the anterior runs forward
and upward to the sphenoidal angle of the parietal,
where it is sometimes converted into a bony canal; the posterior runs lateralward and backward across the temporal squama and passes on to the parietal near the middle of its
lower border. The following apertures are also to be seen. In front is the superior
orbital fissure, bounded above by the small wing, below, by the great wing,
and medially, by the body of the sphenoid; it is usually completed laterally by
the orbital plate of the frontal bone. It transmits to the orbital cavity the oculomotor, the trochlear, the ophthalmic division of the
trigeminal, and the abducent nerves, some filaments
from the cavernous plexus of the sympathetic, and the orbital branch of the
middle meningeal artery; and from the orbital cavity a recurrent branch from the
lacrimal artery to the dura mater, and the ophthalmic
veins. Behind the medial end of the superior orbital fissure is the foramen rotundum, for the passage of the maxillary nerve.
Behind and lateral to the foramen rotundum is the foramen
ovale, which transmits the mandibular nerve, the
accessory meningeal artery, and the lesser superficial petrosal
nerve. 50 Medial to the foramen ovale is the foramen
Vesalii, which varies in size in different
individuals, and is often absent; when present, it opens below at the lateral
side of the scaphoid fossa, and transmits a small vein. Lateral to the foramen ovale is the foramen spinosum,
for the passage of the middle meningeal vessels, and a recurrent branch from
the mandibular nerve. Medial to the foramen ovale is
the foramen lacerum; in the fresh state the
lower part of this aperture is filled up by a layer of fibrocartilage, while
its upper and inner parts transmit the internal carotid artery surrounded by a
plexus of sympathetic nerves. The nerve of the pterygoid
canal and a meningeal branch from the ascending pharyngeal artery pierce the
layer of fibrocartilage. On the anterior surface of the petrous portion of the
temporal bone are seen the eminence caused by the projection of the superior semicircular canal; in front of and a little lateral to
this a depression corresponding to the roof of the tympanic cavity; the groove
leading to the hiatus of the facial canal, for the transmission of the
greater superficial petrosal nerve and the petrosal branch of the middle meningeal artery; beneath it,
the smaller groove, for the passage of the lesser superficial petrosal nerve; and, near the apex of the bone, the
depression for the semilunar ganglion and the orifice of the carotid canal.
The Posterior Fossa (fossa cranii posterior).—The posterior fossa is the largest and deepest of the three. It is
formed by the dorsum sellæ and clivus of the sphenoid, the occipital, the petrous and
mastoid portions of the temporals, and the mastoid
angles of the parietal bones; it is crossed by the occipitomastoid
and the parietomastoid sutures, and
lodges the cerebellum, pons, and medulla oblongata. It is separated from the
middle fossa in and near the median line by the dorsum sellæ
of the sphenoid and on either side by the superior angle of the petrous portion
of the temporal bone. This angle gives attachment to the tentorum
cerebelli, is grooved for the superior petrosal sinus, and presents at its medial end a notch upon
which the trigeminal nerve rests. The fossa is limited behind by the grooves
for the transverse sinuses. In its center is the foramen
magnum, on either side of which is a rough tubercle for the attachment of
the alar ligaments; a little above this tubercle is the canal, which transmits
the hypoglossal nerve and a meningeal branch from the ascending pharyngeal
artery. In front of the foramen magnum the basilar portion of the occipital and
the posterior part of the body of the sphenoid form a grooved surface which
supports the medulla oblongata and pons; in the young skull these bones are
joined by a synchondrosis. This grooved surface is
separated on either side from the petrous portion of the temporal by the petro-occipital
fissure, which is occupied in the fresh state by a plate of cartilage; the
fissure is continuous behind with the jugular foramen, and its margins are
grooved for the inferior petrosal sinus. The jugular
foramen is situated between the lateral part of the occipital and the
petrous part of the temporal. The anterior portion of this foramen transmits the
inferior petrosal sinus; the posterior portion, the
transverse sinus and some meningeal branches from the occipital and ascending
pharyngeal arteries; and the intermediate portion, the glossopharyngeal, vagus, and accessory nerves. Above the jugular foramen is
the internal acoustic meatus, for the facial and acoustic nerves and
internal auditory artery; behind and lateral to this is the slit-like opening
leading into the aquæductus vestibuli,
which lodges the ductus endolymphaticus;
while between these, and near the superior angle of the petrous portion, is a
small triangular depression, the remains of the fossa subarcuata,
which lodges a process of the dura mater and
occasionally transmits a small vein. Behind the foramen magnum are the inferior
occipital fossæ, which support the
hemispheres of the cerebellum, separated from one another by the internal
occipital crest, which serves for the attachment of the falx
cerebelli, and lodges the occipital sinus. The
posterior fossæ are surmounted by the deep grooves
for the transverse sinuses. Each of these channels, in its passage to
the jugular foramen, grooves the occipital, the mastoid angle of the parietal,
the mastoid portion of the temporal, and the jugular process of the occipital,
and ends at the back part of the jugular foramen. Where this sinus grooves the
mastoid portion of the temporal, the orifice of the mastoid foramen may
be seen; and, just previous to its termination, the condyloid
canal opens into it; neither opening is constant.
Theme 2.
Orbit. Nasal cavity
Orbit has a superior, inferior, lateral and medial
walls. Upper wall formed by frontal bone and sphenoid lesser alae. Lower wall composed by maxilla, zygomatic
and palatine bones. Lateral wall formed by zygomatic
bone and sphenoid greater alae. Medial wall consists
of frontal process of the maxilla, lacrimal bone, orbital plate of the ethmoidal bone and sphenoid body.
Orbit opens out that bordered supraorbital and infraorbital margins. Superior orbital fissure positioned
between upper and lateral walls, inferior orbital fissure - lower and lateral
walls.
Laterally one can find fossa for lacrimal gland. Infraorbital sulcus and canal are on the lower wall. Canal
opens by infraorbital foramen in canine fossa on
facial surface of the skull. Anterior and posterior ethmoid
foramen are on medial orbital wall. Orbit communicates with skull cavity by the
optic canals and nasal cavity - through nasolacrimal canal (on medial orbital
wall).
The Orbits (orbitæ)—The orbits are two quadrilateral pyramidal cavities, situated at the
upper and anterior part of the face, their bases being directed forward and lateralward, and their apices backward and medialward, so that their long axes, if continued backward,
would meet over the body of the sphenoid. Each presents for examination a roof,
a floor, a medial and a lateral wall, a base, and
an apex.
Medial wall of left orbit.
The roof is concave, directed downward, and slightly
forward, and formed in front by the orbital plate of the frontal; behind
by the small wing of the sphenoid. It presents medially the trochlear
fovea for the attachment of the cartilaginous pulley of the Obliquus oculi superior; laterally, the lacrimal
fossa for the lacrimal gland; and posteriorly, the suture between
the frontal bone and the small wing of the sphenoid.
The floor is directed upward and lateralward,
and is of less extent than the roof; it is formed chiefly by the orbital
surface of the maxilla; in front and laterally, by the orbital
process of the zygomatic bone, and behind and medially,
to a small extent, by the orbital process of the palatine. At its medial angle
is the upper opening of the nasolacrimal canal, immediately to the lateral side
of which is a depression for the origin of the Obliquus
oculi inferior. On its lateral part is the suture between the maxilla and zygomatic bone, and at its posterior part that between the
maxilla and the orbital process of the palatine. Running forward near the
middle of the floor is the infraorbital
groove, ending in front in the infraorbital canal
and transmitting the infraorbital nerve and vessels.
The medial wall
is nearly vertical, and is formed from before backward by the frontal
process of the maxilla, the lacrimal, the lamina papyracea
of the ethmoid, and a small part of the body of the
sphenoid in front of the optic foramen. Sometimes the sphenoidal
concha forms a small part of this wall.It exhibits
three vertical sutures, viz., the lacrimomaxillary, lacrimoethmoidal, and sphenoethmoidal.
In front is seen the lacrimal groove, which lodges the lacrimal sac, and
behind the groove is the posterior lacrimal crest, from which the
lacrimal part of the Orbicularis oculi arises. At the junction of the medial
wall and the roof are the frontomaxillary, frontolacrimal, frontoethmoidal,
and sphenofrontal sutures. The point of junction of
the anterior border of the lacrimal with the frontal is named the dacryon. In the frontoethmoidal
suture are the anterior and posterior ethmoidal
foramina, the former transmitting the nasociliary
nerve and anterior ethmoidal vessels, the latter the
posterior ethmoidal nerve and vessels.
The lateral wall, directed medialward
and forward, is formed by the orbital process of the zygomatic
and the orbital surface of the great wing of the sphenoid; these are united by
the sphenozygomatic suture which terminates below at
the front end of the inferior orbital fissure. On the orbital process of the zygomatic bone are the orbital tubercle (Whitnall) and the orifices of one or two canals which
transmit the branches of the zygomatic nerve. Between
the roof and the lateral wall, near the apex of the orbit, is the superior
orbital fissure. Through this fissure the oculomotor,
the trochlear, the ophthalmic division of the trigeminal, and the abducent nerves enter the orbital cavity, also some
filaments from the cavernous plexus of the sympathetic and the orbital branches
of the middle meningeal artery. Passing backward through the fissure are the
ophthalmic vein and the recurrent branch from the lacrimal artery to the dura mater. The lateral wall and the floor are separated
posteriorly by the inferior orbital fissure which transmits the
maxillary nerve and its zygomatic branch, the infraorbital vessels, and the ascending branches from the sphenopalatine ganglion.
The base of the orbit, quadrilateral in shape, is
formed above by the supraorbital arch of the frontal bone, in which is
the supraorbital notch or foramen for the passage of the
supraorbital vessels and nerve; below by the zygomatic
bone and maxilla, united by the zygomaticomaxillary
suture; laterally by the zygomatic bone and the zygomatic process of the frontal joined by the zygomaticofrontal suture; medially by the frontal bone and
the frontal process of the maxilla united by the frontomaxillary
suture.
The apex, situated at the back of the orbit,
corresponds to the optic foramen 49 a short, cylindrical canal, which transmits the optic nerve and
ophthalmic artery.
It will thus be seen that there are nine openings
communicating with each orbit, viz., the optic foramen, superior and inferior
orbital fissures, supraorbital foramen, infraorbital
canal, anterior and posterior ethmoidal foramina, zygomatic foramen, and the canal for the nasolacrimal duct.
Bony cavity of the nose opens forward by piriform aperture, backward connects nasopharynx
through choanae. Nasal cavity has a superior,
inferior and medial walls and it is separated by bony septum into right and
left halves.
Lateral wall formed by:
·
nasal bone
·
frontal process of the maxilla
·
lacrimal bone
·
ethmoidal
labyrinth
·
perpendicular plate of the palatine
bone
·
medial plate of the pterygoid process (sphenoid bone)
Upper wall (roof) formed by frontal bone and
cribriform plate (ethmoid bone). Lower wall composed
by bony palatine (alveolar process of the maxilla and horizontal plate of the
palatine bone).
Bony nasal septum consists of perpendicular plate (ethmoid bone) and vomer.
Superior nasal meatus
passes between upper and middle nasal conchae and communicates with sphenoid
sinus through sphenoethmoid recess. Posterior ethmoid cells open into superior nasal meatus
Middle nasal
meatus runs between middle and lower nasal conchae and communicates with frontal (through ethmoid infundibulum) and maxillary (Haimory) sinus (through semilunar
hiatus), and with anterior and middle ethmoid
cells.
Inferior
nasal meatus passes between lower nasal concha and bony
palate; nasolacrimal canal and incisive canal open in it.
Horizontal section of nasal and orbital cavities.)
Sagittal section of skull.
The nasal cavities are two irregular spaces, situated one on either side
of the middle line of the face, extending from the base of the cranium to the
roof of the mouth, and separated from each other by a thin vertical septum.
They open on the face through the pear-shaped anterior nasal aperture,
and their posterior openings or choanæ
communicate, in the fresh state, with the nasal part of the pharynx. They are
much narrower above than below, and in the middle than at their anterior or
posterior openings: their depth, which is considerable, is greatest in the middle.
They communicate with the frontal, ethmoidal, sphenoidal, and maxillary sinuses. Each cavity is bounded
by a roof, a floor, a medial and a lateral wall.
The roof is horizontal in its central part, but
slopes downward in front and behind; it is formed in front by the nasal
bone and the spine of the frontal; in the middle, by the cribriform
plate of the ethmoid; and behind, by the body
of the sphenoid, the sphenoidal concha, the ala of the vomer and the sphenoidal process of the palatine bone. In the cribriform
plate of the ethmoid are the foramina for the
olfactory nerves, and on the posterior part of the roof is the opening into the
sphenoidal sinus.
Medial wall of left nasal fossa.
The floor is flattened from before backward and
concave from side to side. It is formed by the palatine process of the maxilla
and the horizontal part of the palatine bone; near its anterior end is the
opening of the incisive canal.
Roof, floor, and lateral wall of left nasal cavity.
The medial wall (septum nasi)
is frequently deflected to one or other side, more often to the left than to
the right. It is formed, in front, by the crest of the nasal bones and
frontal spine; in the middle, by the perpendicular plate of the ethmoid; behind, by the vomer
and the rostrum of the sphenoid; below, by the crest of the maxillæ and palatine bones. It presents, in front, a
large, triangular notch, which receives the cartilage of the septum; and
behind, the free edge of the vomer. Its surface is
marked by numerous furrows for vessels and nerves and by the grooves for the nasopalatine nerve, and is traversed by sutures connecting
the bones of which it is formed.
The lateral wall is formed, in front, by the frontal
process of the maxilla and by the lacrimal bone; in the middle, by the ethmoid, maxilla, and inferior nasal concha; behind, by the
vertical plate of the palatine bone, and the medial pterygoid
plate of the sphenoid. On this wall are three irregular anteroposterior
passages, termed the superior, middle, and inferior meatuses of the nose. The superior
meatus, the smallest of the three, occupies the middle third of the lateral
wall. It lies between the superior and middle nasal conchæ;
the sphenopalatine foramen opens into
it behind, and the posterior ethmoidal cells
in front. The sphenoidal sinus opens into a recess,
the sphenoethmoidal recess, which is
placed above and behind the superior concha. The middle meatus is
situated between the middle and inferior conchæ,
and extends from the anterior to the posterior end of the latter. The lateral
wall of this meatus can be satisfactorily studied only after the removal of the
middle concha. On it is a curved fissure, the hiatus semilunaris,
limited below by the edge of the uncinate process of
the ethmoid and above by an elevation named the bulla
ethmoidalis; the middle ethmoidal
cells are contained within this bulla and open on or near to it. Through the
hiatus semilunaris the meatus communicates with a
curved passage termed the infundibulum, which communicates in front with
the anterior ethmoidal cells and in rather more than
fifty per cent. of skulls is continued upward as the frontonasal
duct into the frontal air-sinus; when this continuity fails, the frontonasal duct opens directly into the anterior part of
the meatus. Below the bulla ethmoidalis and hidden by
the uncinate process of the ethmoid
is the opening of the maxillary sinus (ostium
maxillare); an accessory opening is frequently
present above the posterior part of the inferior nasal concha. The inferior
meatus, the largest of the three, is the space between the inferior concha
and the floor of the nasal cavity. It extends almost the entire length of the
lateral wall of the nose, is broader in front than behind, and presents
anteriorly the lower orifice of the nasolacrimal canal.
The Anterior Nasal Aperture is a heart-shaped or pyriform opening, whose long axis is vertical, and narrow
end upward; in the recent state it is much contracted by the lateral and alar
cartilages of the nose. It is bounded above by the inferior borders of
the nasal bones; laterally by the thin, sharp margins which separate the
anterior from the nasal surfaces of the maxillæ;
and below by the same borders, where they curve medialward
to join each other at the anterior nasal spine.
The choanæ are each
bounded above by the under surface of the body of the sphenoid and ala of the vomer; below,
by the posterior border of the horizontal part of the palatine bone; laterally,
by the medial pterygoid plate; they are separated
from each other by the posterior border of the vomer.
Peculiarities of foetal skull
Anterior fontanelle
positioned between unfused halves of the frontal
bones. It is overgrown until 1 year old age. Posterior fontanelle
located between parietal and occipital bones. It is overgrown till 2-3 months
age. Mastoid fontanelle (paired) located between
parietal, occipital and temporal bones. It is overgrown in last days before
birth or during first 2-3 months. Sphenoid fontanelle
(paired) located between frontal, parietal, sphenoid and temporal bones. It is
overgrown in last week before birth or during first 2-3 months of life.
Differences in the Skull Due to AgeAt birth the skull is large in proportion to the other parts of the skeleton,
but its facial portion is small, and equals only about one-eighth of the bulk
of the cranium as compared with one-half in the adult. The frontal and parietal
eminences are prominent, and the greatest width of the skull is at the level of
the latter; on the other hand, the glabella, superciliary
arches, and mastoid processes are not developed. Ossification of the skull
bones is not completed, and many of them, e. g., the occipital, temporals, sphenoid, frontal, and mandible, consist of more
than one piece. Unossified membranous intervals,
termed fontanelles, are seen at the
angles of the parietal bones; these fontanelles are
six in number: two, an anterior and a posterior, are situated in the middle
line, and two, an antero-lateral and a postero-lateral, on either side.
The anterior or bregmatic
fontanelle is the largest, and is placed at the
junction of the sagittal, coronal, and frontal sutures; it is lozenge-shaped,
and measures about
extension of the bones which surround them, but sometimes they are the
sites of separate ossific centers
which develop into sutural bones. The posterior and
lateral fontanelles are obliterated within a month or
two after birth, but the anterior is not completely closed until about the
middle of the second year.
Skull at birth, showing frontal and occipital fonticuli.
The smallness of the face at birth is mainly accounted for
by the rudimentary condition of the maxillæ and
mandible, the non-eruption of the teeth, and the small size of the maxillary
air sinuses and nasal cavities. At birth the nasal cavities lie almost entirely
between the orbits, and the lower border of the anterior nasal aperture is only
a little below the level of the orbital floor. With the eruption of the
deciduous teeth there is an enlargement of the face and jaws, and these changes
are still more marked after the second dentition.
The skull grows rapidly from birth to the seventh year, by
which time the foramen magnum and petrous parts of the temporals
have reached their full size and the orbital cavities are only a little smaller
than those of the adult. Growth is slow from the seventh year until the
approach of puberty, when a second period of activity occurs: this results in
an increase in all directions, but it is especially marked in the frontal and
facial regions, where it is associated with the development of the air sinuses.
Obliteration of the sutures of the vault of the skull takes
place as age advances. This process may commence between the ages of thirty and
forty, and is first seen on the inner surface, and some ten years later on the
outer surface of the skull. The dates given are, however, only approximate, as
it is impossible to state with anything like accuracy the time at which the sutures
are closed. Obliteration usually occurs first in the posterior part of the
sagittal suture, next in the coronal, and then in the lambdoidal.
In old age the skull generally becomes thinner and lighter,
but in a small proportion of cases it increases in thickness and weight, owing
to an hypertrophy of the inner table. The most striking feature of the old
skull is the diminution in the size of the maxillæ
and mandible consequent on the loss of the teeth and the absorption of the
alveolar processes. This is associated with a marked reduction in the vertical
measurement of the face and with an alteration in the angles of the mandible.
Skull at birth, showing sphenoidal and mastoid
fonticuli.
Sexual Differences in the Skull Until
the age of puberty there is little difference between the skull of the female
and that of the male. The skull of an adult female is, as a rule, lighter and
smaller, and its cranial capacity about 10 per cent. less, than that of the
male. Its walls are thinner and its muscular ridges less strongly marked; the
glabella, superciliary arches, and mastoid processes
are less prominent, and the corresponding air sinuses are small or rudimentary.
The upper margin of the orbit is sharp, the forehead vertical, the frontal and
parietal eminences prominent, and the vault somewhat flattened. The contour of
the face is more rounded, the facial bones are smoother, and the maxillæ and mandible and their contained teeth
smaller. From what has been said it will be seen that more of the infantile
characteristics are retained in the skull of the adult female than in that of
the adult male. A well-marked male or female skull can easily be recognized as
such, but in some cases the respective characteristics are so indistinct that
the determination of the sex may be difficult or impossible.
Age changes in the face
Deciduous teeth usually begin to erupt in infants of approximately 6
months of age. The body of the mandible elongates particularly posterior to the
mental foramen, to accommodate the development and
then the bearing of eight secondary (permanent) teeth, which begin to erupt during
the 6th year of life. Eruption of these permanent teeth is not
complete until early adulthood. Rapid growth of the face during infancy and
early childhood coincides with the eruption of primary teeth. Vertical growth
of the upper face results mainly from dentoalveolar
development. These changes are more marked after the secondary teeth erupt.
Following complete loss of teeth in old age (or younger if care is neglected),
the alveoli begin to fill in with bone and the alveolar processes begin to
resorb. Concurrent enlargement of the frontal and facial regions is associated
with the increase in the size of the paranasal
sinuses – air-filled extensions of the nasal cavities in certain cranial bones.
Most paranasal sinuses are rudimentary or absent at
birth and develop during 1 – 2 year. Growth of the paranasal
sinuses is important in altering the shape of the face and in adding resonance
to the voice.
Obliteration of the
cranial sutures
The obliteration of sutures between the bones of the calvaria
usually begins between the ages of 30 and 40 on the internal surface and
approximately 10 years later on the external surface. Obliteration of sutures
usually begins at the bregma and continues seguentially in the sagittal,
coronal, and lambdoid sutures.
Age changes in the skull
As people age the skull bones normally become progressivey
thinner and lighter, and the diploe gradually become filled with a gray gelatinous material. In these individuals the bone
marrow has lost its blood cells and fat, giving it a gelatinous appearance.
Craniology
Skulls vary in size and
shape, and the term craniology is applied to the study of these variations. The
capacity of the cranial cavity constitutes a good index of the size of the
brain which it contained, and is most conveniently arrived at by filling the
cavity with shot and measuring the contents in a graduated vessel. Skulls may
be classified according to their capacities as follows:
1.
Microcephalic, with a capacity of less then 1350 c. cm. ,
those of native Australians and Andaman Islanders.
2.
Mesocephalic, with a capacity of less then 1350 c. cm. to
1450 c. cm. , those of African and Chinese.
3.
Megacefalic, with a capacity of over 1450 cm2 – e.g. , those of
Europeans, Japanese and Eskimos.
References:
1.Gray`s
Anatomy. Lawrence H. Bannister, Martin M. Berry, Patricia Collins and others. Churchhill Livingstone, - 1999. 2092 p.
2.
W. Kahle, H. Leonhardt, W. Platzer. Colour atlas and
Textbook of Human Anatomy. –
3.
R.D. Lockhart, G.F. Hamilton, F.W. Fyfe. Anatomy of the human body. –
5. Synelnіkov R.D. The atlas of anatomy of the man. Іn the 4-th volumes. -: Medіcіna, 1991.
6. Lecture.
7. Colіn H. Wheatley, B.Kolz. Human
anatomy and physіology. 1995.
8. Reminetskyy B.Y., Fedonyuk Y.I. Human anatomy. Locomotory
apparatus. notes. ‘Ukrmedknyha’, - 2002, - 136 p.