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78 Tasks for the Veterinary Assistant

anchor point for the skull, thoracic cage, and the appen- extend, contract, or retract to move a body part, and
dicular skeleton. The vertebral column is divided into then relax so the body part can return to “normal.”
five sections (Figure 5.7). Think about walking. It may not seem like a voluntary
The cervical vertebrae make up the neck and have movement, you just walk, right? Wrong, even if you are
seven individual bones including the atlas which con- not aware of it, when your leg starts the movement of a
nects to the skull and the axis which connects to the atlas step you have either consciously or subconsciously com-
cranially and the third cervical vertebrae caudally manded it to do so. Skeletal muscles are attached to
(Figure 5.7). There are 13 thoracic vertebrae that span bones by tendons.
the length of the thoracic cage. Seven lumbar vertebrae Smooth muscles are involuntary muscles that contract
connect to the thoracic vertebrae at the thoracic–lumbar and rest without conscious thought. This is stimulated by
junction. This is often referred to as the TLJ when veter- the autonomic nervous system. Smooth muscle lines
inarians are asking for radiographs of that area. The organs such as the gastrointestinal tract, to move food or
next three vertebrae are fused together and make up the waste through the digestive system. Muscles in the uterus
sacral vertebrae or the sacrum. The last section is the contract to expel a baby. There are muscles in the ure-
coccygeal vertebrae; the number of these can vary thra and bladder for the expulsion of urine. Blood ves-
depending on whether the animal has a natural or sur- sels are lined with muscles to help move the blood
gical dock of the tail. through them and bronchi have muscles to pull air in
The thoracic cage is made up of 13 pairs of ribs; one and push it out of the lungs with the help of the
attaches to each side of the thoracic vertebrae. Ribs 1–12 diaphragm.
are held in place by the sternum, the last rib is called a Cardiac muscle is also involuntary and is autorhyth-
“floating” rib and only attaches at the vertebra. The mic, which means it generates its own action potential.
caudal end of the sternum is called the xiphoid process. Once the muscle contraction starts it moves through the
It is usually palpable and is a landmark for various proce- organ without stopping. It is fueled by blood vessels that
dures in surgery and radiography. bring in oxygen and nutrients and carry away waste prod-
Diseases that can affect the skeletal system include ucts generated by the contraction and relaxation of the
arthritis, an inflammation of the joints which involves muscle tissue. We will spend more time on the cardiac
swelling and pain. Osteoarthritis is the degeneration of muscle when we discuss the cardiovascular system.
joint cartilage causing pain, stiffness, and sometimes the Veterinary assistants need to know the names and
growth of bone spurs. Vertebral disk disease can happen locations of the skeletal muscles. These are the muscles
at any time but like arthritis is often associated with age that are used for locomotion and some of these are used
deterioration. Cancer of the bone, or osteosarcoma, is for injections because of their size. It is interesting to
seen frequently in older, large breed dogs. Bones can note that the names of muscles on four‐legged and two‐
have congenital abnormalities, which include hip and legged animals are very similar, and that includes peo-
elbow dysplasia, which are poorly formed hips and ple! The size and length may be a bit different based
elbows. A young animal may experience panosteitis, upon how the animal developed. Figure 5.9 shows a dog
which is inflammation of the bones. Osteochondritis and Figure 5.10 a horse with the underlying muscles
and osteochondritis dissecans (OCD) are developmental outlined.
diseases that occurs in large and giant breed puppies if Muscles can be affected by disease and trauma. Myopathy
not fed properly. is a general term for muscle disease. Polymyositis is an
inflammation of many muscles. Degenerative myopathy
causes weakness in the affected muscles. More common
Muscular System occurrences of muscle trauma are strains where the muscle
is overstretched. Sprains occur when the ligament is over-
Muscles are made up of bundles of fibers that are covered stretched. Sometime these ligaments tear because a leg
with a thin sheet of fibrous material called fascia. The twists or bends wrongly. A common torn ligament seen in
physiology of muscles is that they contract and relax animals is the anterior cruciate ligament. Tendonitis is when
from nerve impulses. This contraction and relaxation the tendons have become inflamed from repetitive overuse.
mechanism provides locomotion of the body itself.
Muscles also work in other body functions; moving
blood, food, air, and waste products through the body. Cardiovascular System
There are three types of muscles to assist in making these
functions happen. Analogy:
Skeletal muscles are those attached to bones. They Think of the cardiovascular system as a highway system that
are voluntary muscles which means an animal has to serves a major city. The “heart” of any town is the downtown
“command” the muscle to contract and relax via the area, it is connected to the suburbs by high speed roads called
central nervous system. Skeletal muscles contract to lift, “arteries” and slower, smaller “veins” called streets. Arteries are