Agriculture Reference
In-Depth Information
T
HE
R
IBS
The ribs are paired structures, and the numbers of them
correspond to the numbers of thoracic vertebrae (× 2). Each
rib has a bony part and a cartilage at the distal end. The
bony part articulates proximally with two adjacent thoracic
vertebrae and the intervertebral discs, and the cartilage
articulates with the sternum. Depending upon the direct
or indirect attachment to the sternum, the ribs are divided
into two categories: sternal and asternal. The sternal ribs
are eight pairs, whereas the asternal ribs are only fi ve
pairs. The cartilages of the latter form together a cartilagi-
nous arch called costal arch. One rib is illustrated in Figure
6.10 .
The functional anatomy of the thoracic vertebrae,
sternum, and ribs is important for the normal activity of
the respiratory and cardiovascular systems. They build up
the thoracic cavity for the protection of the lungs and the
heart with the major vessels and nerves, lymph nodes, and
the thoracic thymus, and facilitate the act of respiration.
support the body weight; are related to each other by joints;
are the levers that mobilize the body and produce displace-
ment by the contraction of muscles; and some of the
prominences are landmarks for clinical purposes. The
prominences and depressions of the surface of the bones
were modeled during thousands of years of evolution by
pulling the ligaments and contraction of the muscles, to
respond to a species-specifi c life.
THE ARTICULAR SYSTEM (THE JOINTS)
There are three types of joints: mobile, semimobile, and
immobile. The mobile joints (the joints of the limbs) allow
the entire spectrum of movements, while the semimobile
joints (the intervertebral joints) allow very reduced move-
ments. The immobile joints immobilize the bones of the
skull, for example, in the adult life after the brain devel-
opes fully.
The joints of the vertebral column provide for the bodies
and arches of the vertebrae. Intervertebral discs are inter-
posed between two adjacent vertebral bodies. The joints of
the ribs include ligaments between the heads of the ribs
and the bodies of vertebrae and the intervertebral discs
(dorsally), and the cartilages and the sternum (ventrally).
The joints of the sternum provide for the sternebrae.
The joints of the limbs consist of joint capsules and liga-
ments. The joint capsules are fi brous externally, and syno-
vial internally. The fi brous joint capsule is the continuation
of the periosteum from one bone to another. The synovial
membrane, a thin and delicate structure, contains synovial
fl uid, which allows a smooth gliding of the bones against
each other.
Most of the joints of the skull are sutures, with the
exception of the temporomandibular joint (symmetrical),
which is mobile. From the functional point of view, it
allows the movements of the mandible against the rest
of the skull, during the prehension of food and the
mastication process. The movements of the mandible
open or close the mouth, and move laterally during the
mastication (the latter is a species-specifi c feature for
all ruminants).
The Appendicular Skeleton
T
HE
T
HORACIC
L
IMB
The thoracic (fore) limb consists in a proximo-distal
direction of the scapula (the bone of the shoulder), the
humerus (the bone of the arm, or brachium), the radius and
ulna (the bones of the forearm, or antebrachium), the
carpal bones (the bones of the knee), the metacarpal bones
(the bones of the metacarpus), and the phalanges with the
sesamoid bones (the bones of the digits). They are illus-
trated in Figure 6.12. Similar to the skull, the structures
marked with an “L” are landmarks for clinical purposes.
T
HE
P
ELVIC
L
IMB
The pelvic (rear) limb consists in a proximo-distal direc-
tion of the coxal (the bone of the rump), the femur and
patella (the bones of the thigh), the tibia (the bone of the
crus, or leg), the tarsal (the bones of the hock), the meta-
tarsal (the bones of the metatarsus), and the phalanges with
the sesamoid bones (the bones of the digits). A specifi c
note for the coxal bone: it is formed by the fusion of three
bones—the ilium, the pubis, and the ischium. By the pubis
and ischium, the symmetrical bones are articulated with
each other. The bones of the pelvic limb are illustrated in
Figure 6.13. Similar to the skull and the thoracic limb, the
structures marked with an “L” are landmarks for clinical
purposes.
The functional anatomy of the appendicular skeleton
refers to the following roles: they connect with the body;
THE MUSCULAR SYSTEM (THE
SKELETAL MUSCLES)
There are three types of muscles in the body: skeletal,
visceral, and cardiac. Functionally, the skeletal muscles
produce the movement of bones, and contribute to the
standing position and to the displacement of the body.
They are called striated muscles because of a specifi c inti-
mate structure. The visceral muscles mobilize the viscera
