_Sternum._—One of the bones of the thorax; is situated in the middle
line in the front of the chest, and is oblique in direction, the
superior end lying within a few inches of the vertebral column, the
inferior being projected forward so as to be placed at a considerable
distance from the spine. The bone is flat or slightly concave in
front, and marked by five transverse lines, which indicate its
original sub-division into six pieces. It is convex behind, broad
and thick above, where it presents a concave border, and narrow at
its junction with the middle piece. It is divided into the superior
piece or manubrium, the middle piece or body, and the inferior piece,
which is the smallest of the three, and varies in appearance, being
sometimes pointed, at other times broad and thin, and again, at other
times, perforated by a round hole. The seven true ribs are attached
at each side of the sternum by means of the costal cartilage.
_Abdominal Region._—The abdomen is the inferior cavity of the trunk
of the body; it is bounded in front and at the sides by the lower
ribs and abdominal muscles, above by the diaphragm, and below by the
pelvis, and contains the alimentary canal, the organs subservient to
digestion, viz.: the liver, pancreas and spleen, and the organs of
excretion, the kidneys and the supra-renal capsules.
The abdomen may be divided into three regions; in the upper region
will be seen the liver, extending across from the right to the left
side, the stomach and spleen on the left, and the pancreas and
duodenum behind; in the middle region is the transverse part of the
colon, with the upper part of the ascending and descending colon,
omentum, small intestines, mesentery, and behind, the kidneys and
supra-renal capsules; in the inferior region is the lower part of the
omentum and small intestines, ascending and descending colon, and
ureters.
_Fascia_ (from fascia, a bandage) is the name assigned to laminæ
of various extent and thickness, which are distributed through
different regions of the body for the purpose of investing or
protecting the softer or more delicate organs. From a consideration
of their structure, these fasciæ may be arranged into two groups:
areolo-fibrous fascia, and aponeurotic fascia.
The areolo-fibrous fascia is best illustrated by the common
subcutaneous investment of the entire body, the superficial fascia.
This structure is situated immediately beneath the integument over
every part of the frame, and is the medium of connexion between that
layer and the deeper parts; it is composed of areolar and elastic
tissues, and contains an abundance of adipose cells. The fat, being
a bad conductor of caloric, serves to retain the warmth of the body,
while it forms at the same time a yielding tissue, through which
minute vessels and nerves pass to the skin without incurring the risk
of obstruction from injury or pressure.
The aponeurotic fascia is the strongest kind of investing membrane;
it is composed of tendinous fibres running parallel with each other
and connected by other fibres of the same kind passing in different
directions, together with areolar tissue and fine elastic fibres.
In the limbs, it constitutes the deep fascia, inclosing and forming
distinct sheaths to all the muscles and tendons. It is thick on the
outer and least protected side of the limb, and thinner at its inner
side.
The _Skin_ is the exterior investment of the body, which it serves
to cover and protect. It is continuous at the aperture of the
internal cavities with the lining membrane of those cavities, the
internal skin or mucous membrane, and is composed essentially of two
layers—derma and epidermis. The derma or cutis is chiefly composed
of areola-fibrous tissues, besides which it has entering in its
structure elastic tissues and smooth muscular fibre, together with
blood vessels and nerves. The epidermis or cuticle (scarf-skin)
is a product of the derma, which it serves to envelop and defend.
That surface of the epidermis which is exposed to the influence of
the atmosphere and exterior sources of injury is hard and horny in
texture, while that which lies in contact with the under layer is
soft and cellular.
_Viscera._—The viscera of the human body are situated in the three
great cavities—cranio-spinal, thorax and abdomen. The viscera of
the cranio-spinal cavity are the brain, with the spinal cord, and
the principal organs of sense. The viscera of the chest are, the
central organs of circulation, the heart, the organs of respiration,
the lungs. The abdominal viscera admit of a sub-division into those
which properly belong to that cavity, viz.: the alimentary canal, the
liver, pancreas, spleen and kidneys; and those of the pelvis, the
bladder and the internal organs of generation.
_Cartilage._—In the structure of joints, cartilages serve the double
purpose of a connecting and separating medium; in the former capacity
possessing great strength; in the latter, smoothness and elasticity.
For instance, the costal cartilages unite the ribs with the sternum
and form the point of separation by the knife, when it is desired to
raise the sternum, as in the preceding process of embalming.
_Gall Bladder_ is the reservoir of the bile; it is a sac situated in
a fosse on the under surface of the right lobe of the liver.
_Pancreas._—It is a long, flattened, conglomerate gland; it is
about six inches in length, and is situated transversely across the
posterior wall of the abdomen and behind the stomach.
_Supra-Renal Capsules_ are two small, yellowish and flattened bodies
surmounting the kidneys, and inclining inwards and towards the
vertebral column.
_Kidneys_ are the secreting organs of the urine; they are situated in
the lumbar region, and at each side of the vertebral column.
_Pelvis._—The cavity of the pelvis is that portion of the great
abdominal cavity which is included between the bones of the pelvis.
The viscera of the pelvis in the male are the urinary bladder,
prostrate gland and rectum.
_Bladder._—It is a hollow, membranous viscus, triangular and
flattened against the pubes when empty, ovoid when distended, and in
front of and upon the rectum.
_Circle of Willis._—The communications established between the
anterior cerebral arteries in front and the internal cavities and
posterior cerebral arteries behind, by the communicating arteries,
constitute the remarkable vascular communication at the base of the
brain called the circle of Willis.