Page 311 - Anatomy and Physiology of Farm Animals, 8th Edition

296 / Anatomy and Physiology of Farm Animals

The γ‐globulins are synthesized by cells
the cells gradually settle to the bottom, of the immune system. Most of the known
leaving a straw‐colored fluid above. This
VetBooks.ir fluid portion of the blood is plasma. If circulating antibodies are included in the
γ‐globulin fraction. The γ‐globulin content
blood is allowed to clot, the cells are trapped
in a meshwork of clotting proteins, leaving a of the blood therefore increases following
yellow fluid, the serum. Essentially, serum is vaccination and during recovery from
plasma minus the plasma proteins responsi- disease. Immune serum or hyperimmune
ble for producing the clot. serum can be produced by repeatedly
Plasma is about 92% water and 8% other inoculating an animal with a specific anti-
substances. The kidneys are responsible gen. Serum from that animal can then be
for maintaining constant proportions of injected into an animal susceptible to the
water and other constituents of the plasma same disease to provide passive protection
by the selective filtration and reabsorption for as long as the antibodies remain in the
of water and other substances from the susceptible animal. This provides merely
blood plasma. The total osmolality of temporary immunity.
plasma at normal body temperature is
about 290 mOsm/kg. Osmolality is a meas-
ure of the number of osmotically active Blood pH
particles (not the mass of the particles)
per unit of solute. The two predominant A typical pH range for blood is 7.35 to 7.45,
particles in plasma are sodium and chlo- just slightly on the alkaline side of neutral.
ride ions (Table 15‐1), and these contribute The pH of blood is kept within rather nar-
the most to the total osmolality of plasma row limits by a variety of mechanisms that
or serum. include contributions by the kidneys (see
The plasma proteins consist of two major Chapter 23) and the respiratory system
types: albumin and globulins. Albumin is (see Chapter 19). Several chemical buffer
the most prevalent plasma protein and is systems in the plasma also contribute to
the predominant protein synthesized by the the control of blood pH. The most impor-
liver. Many small compounds and electro- tant of these is the bicarbonate buffer sys-
lytes (e.g., calcium ions) bind to albumin tem, and the bicarbonate ion is the base in
and circulate in plasma in this bound form. this system. The bicarbonate ion is the
This prevents their rapid loss in the urine. second most prevalent anion in plasma
Because albumin and other large proteins (Table 15‐1). In acidosis or acidemia the
do not readily pass through capillary walls, blood pH is abnormally low, and in alkalo-
they also provide an effective osmotic force, sis or alkalemia the pH is abnormally high.
termed oncotic pressure, that prevents
excessive fluid loss from capillaries into the
interstitium. Hemostasis and Coagulation
The globulins in serum or plasma may
be classified according to their migration Hemostasis, the stoppage of bleeding,
(separation) by electrophoresis. α‐ may involve three basic reactions: (1) con-
Globulins and β‐globulins are classes that striction by the smooth muscle of the
are synthesized in the liver. Members of injured vessel to decrease the size of the
these classes have a variety of functions, opening and increase the resistance to
including transport in a manner similar to flow out of the vessel; (2) formation of a
albumin, body defense (see Chapter 16), platelet plug to occlude the opening; and
and blood clotting. Many of the globulin (3) clot formation to complete occlusion
proteins are inactive precursors of enzymes of the opening. Injuries to vessels do not
or substrates for enzymes involved in require the formation of a clot (coagula­
blood clotting (discussed later in this tion) if hemostasis can be achieved by the
chapter). first two reactions.