Page 308 - Anatomy and Physiology of Farm Animals, 8th Edition

Blood and Other Body Fluids / 293

teins that act as antigens, and agglutination
results if erythrocytes with specific anti-
VetBooks.ir gens are added to a solution containing

appropriate antibodies. Blood typing is a
general term describing the procedures
used to identify the antigen or antigens in a Plasma
given blood sample. Clumping may occur (~55%)
during transfusions of blood within the
same species, such as between humans, if
blood of the wrong type (i.e., containing the Leukocytes and platelets
wrong combination of antigens) is used. At (buffy coat)
least seven blood types have been identified
in horses, and it is desirable to ensure that
there is adequate matching of types before Erythrocytes (hematocrit)
attempting transfusions between horses. (~45%)
Blood typing has also been done in cattle
and dogs, but usually a single transfusion
can be done between two cattle or between
two dogs with little difficulty. However, Figure 15-3. Layering of blood components in
repeated transfusions can be problematic, an anticoagulated and centrifuged blood sample.
because the initial transfusion may provide
unmatched antigens that stimulate the Hemoconcentration is a decrease in the
formation of antibodies. Blood types are fluid component of blood with a resulting
inherited in all species, and they are often increase in the ratio of cells to fluid. It is
used to establish and monitor pedigrees. indicated by an excessively high erythro-
Anemia (from the Greek an‐, without;
‐emia, blood) results if either the number cyte count (polycythemia) or a high hema-
tocrit. Reductions in plasma volume may
of functional erythrocytes or the quantity result from inadequate water intake or
of hemoglobin per unit of blood is below excessive loss of fluids from the body, such
normal. Anemia may be due to deficient as with vomiting or diarrhea.
blood formation, as with diseases of the
bone marrow, kidney disease with inade-
quate production of erythropoietin, or Platelets
poor nutrition, including dietary deficiency
of iron, copper, vitamins, or amino acids. Blood platelets, also called thrombocytes,
Anemia may also be caused by accelerated are fragments of megakaryocytes, large
loss or destruction of erythrocytes, such as cells formed and residing in the bone
with hemorrhage or parasites. marrow. Thrombocytes are the smallest of
The hematocrit (packed cell volume) the formed elements in the blood at 2 to
is the percentage by volume of whole 4 μm. They are surrounded by a plasma
blood that is erythrocytes. Routine hem- membrane and contain some organelles,
atocrit determinations require a glass but not nuclei. Thrombocytes range from
tube treated to inhibit blood clotting 150,000 to 500,000 per microliter of blood
(hematocrit tubes). Hematocrit tubes in most mammalian species (Table 15‐2).
containing blood are centrifuged until The appearance of platelets in a stained
the blood cells are packed in the lower smear may be considerably different from
end of the tube (Fig. 15‐3). Hematocrits their actual appearance in circulating
typically range from from 35-45% of total blood, where they are oval disks. In smears
blood volume for most mammalian spe- they may appear as circular disks, star‐
cies and are generally considered to be an shaped fragments, or clumps of irregular
indicator of the total erythrocyte count. shape (see Fig. 1‐9).