Page 66 - Headlines Histology2024_Neat

BLOOD

• Blood is one of the body fluid that is formed of a variety of cells suspended in
a fluid medium, the plasma.

BLOOD CELLS

• The blood cells are grouped into three main categories: red blood cells
(erythrocytes), white blood cells (leukocytes) and blood platelets
(thrombocytes).

Red blood cells (Erythrocytes)

• The mature red cells of domestic mammals are non-nucleated, biconcave discs.
• In pig and goat, red blood cells have no biconcavity and therefore appear as

flattened discs.
• In tylopoda (camels and ilama), they are elliptical, biconcave and non-

nucleated. In birds, reptiles, fishes and amphibian, they are oval, biconvex and
nucleated.
• The size of RBCs range from 4-7 ?m, the largest erythrocyte is found in the
dog (7?m) and the smallest in the goat (4 ?m).
• The number of the RBCs varies among species, in dog is about 7 million/mm3,
cattle 6.3 million, goat 14 million and horse 9.5 million.
• With LM, the erythrocytes in a stained blood smear are stained pink due to
their high content of hemoglobin. They have a central pale staining region due
to their biconcave disc shape.
• The erythrocytes sometimes adhere to each other via their broad surface and
become arranged in long chains similar to a stack of coins. This arrangement is
called rouleaux.
• With EM, the shape of the erythrocytes depends on the plane of section
through the cell. The cytoplasmic content of erythrocytes appears electron
dense due to the iron atoms of hemoglobin.

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