process.
Maxillary
ttiberosity.
Nasal and lacrymal bones in situ. (Gray.)
The Lacrymal Bones. These bones are paired.
They are very small and thin, found at the anterior
and internal part of the orbit. The outer surface of
this bone forms with the lacrymal notch of the superior
maxilla the orifice of the nasal duct. (The latter is
the entrance of the canal for the passage of the tears
from the eye to the nasal cavity.)
The Maxillae Bones. They are paired, irregular in
shape, and the principal bones of the face, each sup-
porting the upper teeth of one side, helping to form
68 OSTEOLOGY
the floor and outer walls of the nasal fossae and the
hard palate or roof of the mouth, in conjunction with
the palate bone, also a part of the floor of the orbit.
It contains the hollow space just above the canine
tooth, called the antrum of Highmore. The latter
communicates with the nasal chamber and is frequently
the seat of inflammation. This bone articulates with
its fellow of the opposite side, the nasal, lacrymal,
frontal, ethmoid, palate, malar, vomer, inferior tur-
binate, and sometimes the sphenoid.
The Palate Bones. They are two in number situated
at the back part of the nasal fossae; they are lodged
between the maxilla and the pterygoid processes of
the sphenoid. Each bone assists in the formation of
the floor and outer wall of the nasal cavity, roof of the
mouth, and floor of the orbit.
The Turbinated Bones. They are situated one on
each side of the outer wall of the nasal fossae. Each
consists of a layer of thin, spongy bone, curled upon
itself like a scroll hence its name, turbinated
The Malar Bone. This bone is quadrangular, and is
situated at the upper and outer part of the face. It
forms the prominence of the cheek, part of the outer
wall and floor of the orbit, and part of the temporal
and zygomatic fossae. It articulates with the frontal,
sphenoid, temporal, and the maxilla.
The Mandible or Lower Jaw. This is the largest and
strongest bone of the face. It consists of a horizontal
portion called the body, which forms the chin, and
two perpendicular rami, which join the body to form
the angle of the jaw. It articulates by its condyles
with the glenoid cavity of the tympanic portion of the
temporal bone. The horizontal portion serves for
the lodgement of the lower teeth.
The Hyoid Bone. This is a bony arch, shaped like
a horseshoe, and consisting of five segments a body,
two great cornua, and two lesser cornua. It is situated
in the neck in the receding angle below the chin. It is
BONES OF THE HEAD
69
supported by the stylohyoid ligaments attached to the
lesser cornua of each side.. The attachment of muscles
help to hold this bone in position and acts as a fixed
point for the muscles of swallowing and articulating.
Below it is attached to the larynx by the thyrohyoid
membrane. The hyoid bone can be felt just above
the Adam's apple (pomum Adami). It also affords
attachment to the muscles which lower the jaw,
depress the tongue, and aid as accessory muscles of
respiration.
Orbital surface
Infraorbital groove " - ,
Inferiortetnporal
surfi
Post, dental canals^
Maxillary tubcrusity
Mi c process -
Fron t at process
' f .Zacri/nal margin
Jnfraoroital margin
Anterior surface
Jnfraorbital foramen
^,.- Canine fossa
- ' ' 'Palatine pro cess
. . - .Ant. nasal spine
Alveolar process
Right upper jaw bone, maxilla, from without.
The Skull as a Whole. At birth the skull is large
in comparison with the other parts of the skeleton.
The face is small and equals only about one-eighth
of the bulk of the cranium, as compared to the size of
the face in the adult which equals about one-half of
the size of the skull. Ossification of the bones of the
skull in the infant is not complete; they are held together
by membranous tissue and these intervals between the
bones are termed fontanelles. There are six: Two,
70
OSTEOLOGY
anterior and posterior, and four, an anterolateral and
posterolateral on either side.
FIG. 33
Skull at birth, showing the anterior and posterior fontanelles. (Gray.)
FIG. 34
The lateral fontanelles. (Gray.)
The anterior fontanelle is the largest and is situated
at the junction of the sagittal, coronal, and inter-
frontal sutures; it is lozenge-shaped and measures
PLATE I
Anterior Aspect of the Skull.
PLATE II
Lateral Aspect of the Skull,
BONES OF THE HEAD 71
about 1-J inches from before backward and 1 inch
from side to side. Pulsation can be felt over this
fontanelle up until the twelfth to twenty-fourth
month. It usually disappears by ossification after the
second year, but cases have been reported when it
persists throughout life.
The posterior fontanelle is triangular in form and
is situated at the junction of the superior angles of the
parietal bones with the occipital bone. The lateral
fontanelles are irregular in shape, and are located at
the antero-inferior and postero-inferior angles of the
parietal bones respectively. The posterior and lateral
fontanelles close shortly after birth. The lack of
ossification in the bones of the skull favors the over-
lapping of the bones or moulding of the infant's head
during parturition, thus facilitating delivery and pre-
venting injury to the mother and child; of course,
barring some abnormal condition at the time of birth.
In adults the skull bones are closely fitted by uneven
edges, there being interposed a little fibrous tissue
continuous with the periosteum, the dentations are
confined to the external table, the edges of the inner
table lying in apposition. The lower jaw has a mov-
able articulation differing from the others.
The bones forming the vertex or superior surfaces
of the skull are: frontal, two parietal, two temporal
(squamous and mastoid portions), and great wing of
the sphenoid.
The Orbital Fossae or Orbits. These are pyramidal
in shape, with their bases turned forward and outward.
They are just below the supraorbital arches; their
inner walls are nearly parallel and the outer walls
diverge at slight right angles to each other. Each
is formed by seven bones or eleven for the two orbits
the frontal, sphenoid, ethmoid, lacrymal, palate,
malar, maxilla. The roof of each is formed by the
orbital plate of the frontal and small wing of the
sphenoid; the floor, by the malar, maxilla, and orbital
72 OSTEOLOGY
plate of the palate; inner wall, by the nasal process
of the maxilla, lacrymal, ethmoid, and body of the
sphenoid; outer wall, by the malar and frontal and
great wing of the sphenoid.
The Nasal Fossa or Cavities. These are placed one
on each side of a median vertical wall. They open in
front by the anterior nasal aperture (nares) and behind
by the posterior nares. They communicate with the
sinuses (air spaces) of the frontal, sphenoid, and antruin
of Highmore, the latter is in the body of the maxilla,
and the ethmoidal cells. Thus the danger from infec-
tion entering these air spaces following an abscess for-
mation, influenza, etc., may readily be understood.
THE VERTEBRAL COLUMN AS A WHOLE
The vertebral or spinal column is a central axis upon
which other parts are arranged, situated in the median
line at the posterior part of the trunk; above it sup-
ports the head, by having the first vertebra receive
the condyles of the occipital bone; laterally, the ribs,
and it rests on the sacrum. It is made up of thirty-
three separate vertebrae, imposed one upon the other
with an intervertebral layers of cartilages between
each one, and held in firm relationship by means of
ligaments.
The vertebrae are divisible into seven cervical,
twelve thoracic, five lumbar, five sacral, and four
coccygeal. The cervical, thoracic, and lumbar verte-
brae remain separate throughout life, and are known
as true or movable vertebrae; but the sacral and coccy-
geal vertebrae are firmly united in the adult, so as to
form two bones five entering into the formation of
the sacrum and four into the terminal bone of the
spine or the coccyx. The sacral and coccygeal verte-
bras are called the immovable vertebrae.
The average length of the vertebral column is about
FIG. 35
1st cervical
or Atlas.
Sacrum
Coccyx.
Lateral view of the vertebral column. (Gray.)
74 OSTEOLOGY
twenty-six to twenty-seven inches measured along the
curved anterior surface of the column. The cervical
part measures about five, the thoracic about eleven or
twelve, the lumbar about seven inches, and the sacrum
and coccyx the remainder.
Viewed from the side it presents several curves.
The cervical curve commences at the odontoid process
of the second vertebra, and ends at the middle of the
second thoracic ; it is convex in front, but not as marked
as the other curves. The thoracic curve is concave
forward, commences at the middle of the second thor-
acic, and ends at the middle of the twelfth thoracic.
The lumbar curve, commences at the middle of the
twelfth thoracic and ends at the sacrovertebral angle
(about the junction of the sacrum with the fifth lum-
bar vertebra). It is convex in front; the convexity
being more marked in the lower three lumbar verte-
brae. These curves and convexities are formed by the
bodies of the vertebrae. While the posterior aspect is
formed by the extending spinous processes which usually
can be felt underneath the skin and fascia, no matter
how stout the individual. Laterally the column
presents the transverse processes. The spinal cord,
membranes, origin of spinal nerves, and blood-supply
are within the spinal canal formed by the inter-
vertebral fibrocartilage, body, and arched lamina of
the vertebrae; the latter fusing posteriorly, complete
its boundaries. Posteriorly, the spinous processes
occupy the median line, in a depression known as the
vertebral groove running along the middle of the
back. In the cervical region the processes are short
and bifid, sloping backward and a little downward.
The seventh cervical is the most prominent and can
always be seen and felt beneath the skin, therefore its
name vertebra prominens. The thoracic processes are
oblique above, more oblique in the middle, and below
are nearly horizontal; in the lumbar region they are
horizontal. The transverse processes of the atlas are
THE VERTEBRAL COLUMN AS A WHOLE 75
long; of the axis, short; then extending in size until
the first thoracic is reached, thence diminishing to the
last dorsal, and becoming suddenly much longer in the
lumbar region.
The intervertebral foramina are always in front
of the articular processes excepting those of the atlas
and the upper ones of the axis. They are named from
the upper of the two vertebrae which go to form them,
excepting in the cervical region, where there are eight,
the fissure between the skull and atlas being called
the first. The spinal canal is narrowest in those por-
tions having the least motion, viz., the dorsal and sacral
regions. It is round and f- of an inch in diameter
in the dorsal region; it is triangular, with the apex
behind, in the cervical and lumbar regions; and
largest of all in the cervical region. The cervical
vertebrae each have a foramen (costotransverse) in
their two transverse processes for the vertebral artery.
FIG. 36
Anterior
tubercle of trans-
verse process.
Foramen for vertebral
artery.
Posterior tubercle q
transverse process.
'ransverse
process.
Superior
articular
process.
Inferior
rticular
process.
A cervical vertebra. (Gray.)
General Characteristics of a Vertebra. A typical
vertebra is made up of two parts, an anterior solid
76
OSTEOLOGY
portion, and a posterior portion, the arch or neural
canal. The arch is formed by two pedicles, and two
laminae, supporting seven processes viz., four articular,
two transverse, and one spinous. Taking a typical
vertebra the tenth thoracic, for example. The body
is cylindric; the upper and lower surfaces are flat,
with a rim around the circumference. The front
Superior articular process.
Demi-facet for head of rib.
Facet for tubercle of rib.
Demi-facet for head of rib.
Inferior articular process.
A dorsal vertebra. (Gray.)
and sides are convex from side to side and concave
from above downward. The back is slightly concave
from side to side. The neural arch is completed
laterally by two processes of bone arising from the
postero-external aspect of the body, called pedicles,
and the latter continue as lamina behind, where
they meet to complete the posterior aspect of the neural
arch. The upper and lower borders of the pedicles
THE VERTEBRAL COLUMN AS A WHOLE 77
form intervertebral notches, which complete, with the
neighboring pedicle of the vertebra, intervertebral
foramina. The spinous process projects backward
from the junction of the two laminae. The transverse
processes, one on either side, project outward from
the arch at the junction of the pedicle with the lamina.
The articular processes, two superior and two inferior,
extend upward and downward respectively at the point
of origin of the transverse processes.
FIG. 38
Transverse
process
fiiagrahi of section of odontoid,
process.
Diagram of section of
transverse liyainent.
Foramen fur
vertebral ttrten,
Groove for vertebral artery
and 1st cervical nerve.
Rudimentary spinous process..
First cervical vertebra or atlas. (Gray.)
The Atlas (First Cervical Vertebra). This, sometimes
called rotation vertebra, has no body or spinous
process, but is a large ring with articular and transverse
processes. The posterior part of the ring or arch
corresponds to the neural canal of the other vertebrse;
the anterior part is occupied by the odontoid process
of the axis (second cervical vertebra). This first
vertebra and its relation with the odontoid process
of the axis, below, and its superior articular surface
receiving the condyles of the occipital bone, held in
position by ligaments, permits the head to rotate and
bend forward and backward, as in turning the head
from side to side, and in nodding. The odontoid
process of the axis is held in position by a transverse
78
OSTEOLOGY
ligament passing posterior to it and attached to the
tubercle on the the inner surface of the lateral mass
on either side of the arch, and by check ligaments
extending from the apex of the odontoid process to the
occipital bone. The atlas has a foramen (the costo-
transverse) for the vertebral artery in its transverse
process.
FIG. 39
Odontoid process.
Rough surface for check ligaments.*
Articular surface for transverse ligament. .
Spi nous process.
Articular surface foi
Body.
T Transverse process.
Inferior articular process.
(Gray.)
Second cervical vertebra or axis.
The Axis (Second Vertebra) .This possesses a strong,
prominent process, tooth-like in form, which arises
perpendicularly from the upper surface of the body.
The body in front overlaps the vertebra below. The
tip of the odontoid process affords attachment to the
check ligaments (see Fig. 52, page 109) and has an
articular surface anteriorly, which articulates with the
atlas, and an articular facet behind for the transverse
ligament, which holds it firmly in position. The pedi-
cles and laminae form the neural arch in the same
manner as the atlas and other vertebrae. The spinous
process is larger than the one of the atlas. The trans-
verse processes are small, and are perforated by the
foramen for the vertebral artery.
THE THORAX AS A WHOLE 79
The Sacrum and Coccyx. The sacrum and coccyx
are the result of the fusing of the lower nine vertebrae
into two bones, five to form the sacrum and four the
coccyx.
The sacrum is much larger than the coccyx, is
located between the two iliac bones, articulating
above with the fifth lumbar vertebra, below with the
coccyx, and is perforated with foramina which transmit
the spinal nerves.
The coccyx is pyramidal. Its vertebrae are very
rudimentary, and it possesses a trace of the neural
arch and transverse processes of the typical vertebra.
THE THORAX AS A WHOLE
The thorax is an osseocartilaginous cage, conical and
flattened from before backward. The short antero-
posterior diameter is characteristic of man, but in the
lower mammals and human fetus it is longer than the
transverse diameter. The posterior surface is convex
forward, formed by the twelve thoracic vertebrae and
back part of ribs; on either side the sulcus pulmonalis
is formed by the ribs as they project backward, so
that the weight of the body is more equally distrib-
uted around the vertebral column. The anterior
surface is flattened and slightly convex, is formed by
the sternum and costal cartilages, and lies at an angle
of 20 or 25 degrees with the posterior. A horizontal
anteroposterior diameter taken from the base of the
ensiform is 8 inches (20 cm.); the transverse at the
eighth or ninth ribs is 11 inches (28 cm.); the vertical
anteriorly is 6 inches (15.5 cm.); and posteriorly is
12 inches (31.5 cm.). The lateral surfaces are convex;
formed by the ribs, separated from each other by the
spaces (intercostal).
The superior or upper opening of the thorax, the inlet,
is reniform in shape, being broader from side to side
80
OSTEOLOGY
than before backward. It is bounded behind by the
first thoracic vertebra; in front, by the upper border
of the sternum, and on either side by the first rib.
FIG. 40
First thoracic
The thorax. Ventral view. (Gray.)
It slopes downward and forward so that the anterfor
boundary is on a lower level than the posterior. The
anteroposterior diameter is about 2 inches (5 cm.),
THE THORAX AS A WHOLE 81
and the, transverse about 4 inches (10 cm.). The
parts which pass through the upper opening are,
from before backward in or near the middle line the
sternohyoid and sternothyroid muscles, the remains
of the thymus gland, the trachea (windpipe), the
esophagus (gullet), thoracic duct, inferior thyroid
veins, longus colli muscle of each side, bloodvessels
and nerves.
The inferior or lower opening is formed by the twelfth
thoracic vertebra behind, by the twelfth ribs at the
sides, and in front by the eleventh, tenth, ninth,
eighth, and seventh costal cartilages, which ascend
on either side to form the subcostal angle, from the
apex of which the ensiform cartilage projects. The
lower opening is wider transversely than from before
backward. It slopes obliquely downward and back-
ward, so that the cavity of the thorax is much deeper
behind than in front. The diaphragm closes in the
opening forming the floor of the thorax, and has passing
through it the inferior vena cava, the esophagus,
and vagi nerves, the aorta, thoracic duct, vena azygos
major, and sometimes splanchnic nerves.
The thorax contains the lungs and their pleurae,
the heart and its pericardium, the aorta and branches,
and the structures mentioned under the upper opening,
which pass through it.
The female thorax differs from the male as follows:
general capacity is less, sternum is shorter, the upper
margin of the sternum is on a level with the lower
part of the body of the third thoracic vertebra (in the
male it is the body of the second thoracic vertebra),
the upper ribs are more movable, and thus allow a
greater expansion of the upper part of the thorax than
in the male (Gray) .
The Sternum or Breast Bone. This is a flat, narrow
bone, situated in the median line of the front of the
chest, and in the adult consists of three portions. It
is likened to an ancient sword; the upper piece,
6
82
OSTEOLOGY
representing the handle, is called the manubrium;
the middle and larger portion, which resembles the
blade, is the gladiolus; and the inferior piece, which
resembles the point of the sword, is called the ensiform.
The Ribs (Costse). There are twelve pairs, one on
each side. They are obliquely placed, running forward
and downward. The obliquity increases from above
downward to the ninth rib, when it reaches the
maximum; from this point downward it decreases.
The first seven pairs, attached by costal cartilages
to the sternum, are called sternal, true, or vertebro-
sternal ribs, the remaining lower five pairs are asternal
or false ribs; each of the upper three pairs of false
ribs has its cartilage attached to the cartilage above
it, and are called vertebrochondral ribs; the last two
pairs are attached to the vertebra behind and their
anterior extremity is free; they are called floating or
vertebrarribs.
FIG. 41
For posterior costotransverse ligament.
For anterior costotransverse ligament.
Facet for body of
upper thoracic vertebra.
Ridge for inter-
articular ligament.
Facet for body of
lower thoracic vertebra.
For transverse process of
lower dorsal vertebra.
Vertebral extremity of a rib; external surface. (Gray.)
A Typical Rib. Each rib has an anterior and pos-
terior extremity. The anterior extremity is hollowed
into a pit for union with the costal cartilage. The
posterior extremity is divided into a head, a neck, and
a tuberosity. The head has an upper and lower artic-
ular facet for articulation with the two vertebrae,
above and below; and between the two facets a ridge
for the attachment of the interarticular ligament.
THE THORAX AS A WHOLE 83
The first rib is the shortest, most curved, and the
broadest, the eighth the longest, after which they
decrease in length to the twelfth; the twelfth is the
narrowest.
The Peculiar Ribs. The first rib is short, curved,
and not twisted. Its surfaces look upward and down-
ward. Head is small; neck is slender and rounded;
angle coincides with the tuberosity, which is strong
and placed on the outer margin of the rib. The upper
surface presents close in front of the tuberosity a
rough impression for the scalenus medius muscle, and
in front of the latter two smooth impressions with
an intervening ridge; the posterior impression lodges
the third portion of the subclavian artery, the ridge
affords attachment to the scalenus anticus muscle, and
the anterior impression receives the subclavian vein.
The second rib is not twisted and has no angle; it
presents near its middle an impression for the scalenus
posticus muscle and two serrations of the serratus
magnus.
The tenth rib has but one articular facet, usually.
The eleventh and twelfth ribs are short, have single
articular facets, and only slight elevations to mark
the tuberosities which do not articulate with the trans-
verse processes of the vertebra?. They are pointed
anteriorly. The eleventh has a slight subcostal groove;
the twelfth has no angle.
There may be thirteen ribs. The twelfth rib measures
from 1 to 8 inches.
The Costal Cartilages. These prolong the ribs to
the sternum and increase the elasticity of the thorax.
They consist of white hyaline cartilage. The first
seven pair connect the ribs and sternum, the next
three pair with the lower border of the cartilage of the
preceding rib. The cartilages of the last two ribs
(floating) have pointed extremities which terminate
in free ends. They increase in length from the first
to the seventh, then gradually diminish to the last.
84 OSTEOLOGY
They have an anterior and posterior surface, and a
superior and inferior border. Their articulations with
the sternum and ribs are fixed by attached ligaments.
THE BONES OF THE UPPER EXTREMITY
. ,, /Clavicle (collar bone).
Shoulder girdle ( Scapula (shoulder blade) .
Upper limb'
Arm (brachium, humerus (arm bone).
Forearm (antebrachium, radius, ulna (forearm bones).
(Carpus (wrist bones).
Hand (manus) i Metacarpus (bones of palm).
[Phalanges or bones of digits (fingers).
The Clavicle. This bone forms the anterior por-
tion of the shoulder girdle. It is a long, thin bone,
curved somewhat like the letter /, and placed nearly
horizontally at the upper and anterior part of the
chest, immediately over the first rib. Its inner or
sternal end articulates with the upper border of the
sternum, and its outer or acromial end unites with
the acromion process of the scapula^ the two together
connect the upper limb with the trunk by means of
ligaments.
The Scapula (Shoulder-blade). This is a large, flat
bone, situated at the back and outer aspect of the chest,
between the second and seventh ribs. Its posterior
border is about 1 inch from and parallel with the
vertebral spines. It is attached to the trunk by the
clavicle, fascia, and muscles; and from it is suspended
the humerus by means of the capsular ligament of the
shoulder-joint, which is attached to the margins of