The total body fluid is distributed mainly between two compartments: the extracellular fluid and the intracellular fluid . The extracellular fluid is divided into the interstitial fluid and the blood plasma.


Blood composition:

Blood is composed of a fluid part termed plasma and corpuscles or cells which float in the plasma. Three classes of blood cells are ‘:~,recognized: erythrocytes or red cells, leukocytes or white cells, and thrombocytes or platelets.

Blood color: The red color of blood is imparted by the hemoglobin contained within the erythrocytes. Plasma is yellow to colorless .The color of plasma results principally from the presence of bilirubin, a degradation product of
hemoglobin. In cats, dogs, sheep, and goats, it is colorless or only slightly yellow. It is a darker yellow in the cow and  even darker in the horse, which has a relatively high bilirubin concentration.

Functions of Blood:

The functions of blood are generally related to transport (e.g.,nutrients, oxygen, carbon dioxide, waste products,hormones,heat, and immune bodies).There are additional functions of blood relating to its role in maintaining fluid balance and pH equilibrium in the body.

(I) It carries nutrient substances from the alimentary canal to the tissues.

(2) It transports oxygen from the lungs to the tissues.

(3) It removes the waste products of metabolism from the tissues to the organs of excretion.

(4) It transports the secretions of the endocrine glands.

(5) It aids in the equalization of the water content of the body.

(6) Because of its high specific heat it is an important aid in equalizing body temperature.

(7) It is concerned·. in the regulation of the hydrogen ion concentration in the organism.

(8) It assists in the body defenses against microorganisms.

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