Page 28 - Anatomy and Physiology of Farm Animals, 8th Edition

Introduction to Anatomy and Physiology / 13

cartilage gives shape and rigidity to the granulocytes. Agranulocytes are of two
kinds: monocytes, large cells that engulf and
external ear. Fibrocartilage consists of a
VetBooks.ir mixture of cartilage and collagenous fibers, destroy foreign particles, and lymphocytes,
which usually are smaller and are associated
which forms a semielastic cushion of great
strength. The intervertebral disks between with immune responses. An excess of
the bodies of adjacent vertebrae are com- agranulocytes tends to be associated with
posed of fibrocartilage. chronic types of diseases.
Bone is produced by bone‐forming Granulocytes (polymorphonuclear
cells called osteoblasts. These cells pro- leukocytes) are of three types and are
duce osteoid tissue, which later becomes described according to their affinity for dif-
calcified to form bone. The bone may be ferent stains: granules in neutrophils stain
arranged in the form of spicules (small indifferently; basophils have dark‐staining
spikes) and flat plates, forming a sponge- granules when stained with common blood
like network called cancellous bone, or stains; and eosinophils have red‐staining
spongy bone. Alternatively, osteoid may granules. Blood platelets (thrombocytes)
be laid down in the form of laminated cyl- are small, irregularly shaped cellular frag-
inders (Haversian or osteonal systems), ments that are associated with the clotting
closely packed together to form compact of the blood. Mammalian platelets lack a
bone (Fig. 1‐8). nucleus.
Blood consists of a fluid matrix (liquid Plasma is the fluid part of unclotted
portion), the plasma, a variety of cells blood. Plasma is particularly useful as a
(Fig. 1‐9), proteins, monosaccharides substitute for blood in transfusions because
(simple sugars), products of fat degrada- the proteins in it give it the same osmotic
tion, and other circulating nutrients, pressure as blood. Plasma therefore will
wastes, electrolytes, and chemical inter- not escape from blood vessels as readily as
mediates of cellular metabolism. It is an electrolyte solution (e.g., saline).
sometimes considered to be a connective Serum is the supernatant fluid that
tissue because of the origin of some of its remains after a clot forms and incorporates
components. the cellular components of blood. It is
Red blood cells (RBCs) are also called similar to plasma, but lacks most of the
erythrocytes. In most domestic mammals clotting factors because they were used
they are nonnucleated biconcave disks that to make the clot. Serum is sometimes
contain the protein hemoglobin. The main administered for prevention and treat-
function of the RBCs is to carry hemo- ment of diseases because it contains the
globin. Hemoglobin in turn has the pri- antibody fractions of the blood.
mary function of carrying oxygen from
the lungs to all tissues of the animal. At
the tissue level, oxygen is released to the Muscle Tissue
cells, while carbon dioxide, which is pro-
duced by the cells, diffuses into the blood The three types of muscle tissue are skel-
to be carried back to the lungs, where it etal, smooth, and cardiac (Fig. 1‐10).
can be eliminated during breathing. Both skeletal and cardiac muscle cells
Anemia is a reduction in the concentra- consist of fibers that under the microscope
tion of functional RBCs in the blood. It show characteristic cross‐striations, so
can result from a loss of red cells (as in both are classified as striated muscle.
hemorrhage), insufficient RBC produc- Smooth muscle cells lack distinct cross‐
tion, or inappropriate or premature deg- striations.
radation of the red cells. Each skeletal muscle cell must have its
White cells (also called leukocytes) are own nerve supply, and when stimulated,
one of the body’s first lines of defense against the whole fiber contracts. This is the all‐or‐
infection. They include agranulocytes and none law of muscle contraction. However,