Composition and Function

Blood is the fluid which circulates through the heart, arteries, and veins.  It is mixed with lymph, its corpuscles being suspended in a fluid called blood-plasm (or plasma). The arterial blood is of a lighter red than the venous, which is more purple blood.

Blood composition

Blood shows the following composition:-
1.  Red blood corpuscles or cells, oval, flat disks, with rounded-off margins and a central nucleus which forms a slight swelling: they contain a substance known as haemoglobin, which, combining with the oxygen of the blood, causes the latter's red colour. These red corpuscles are present even in a small drop of blood in innumerable numbers. In birds, red corpuscles are largest in the Cassowary, smallest in Humming-bird, their smallest axis measuring about 1/110 or 1/175 mm,  their largest axis from 1/59 to 1/105 mm.

2.  White blood or lymph corpusclesby far less numerous, colourless and of very variable size (from 1/500 mm to 1/100 mm) showing lively amoeboid motions.  These aid in the body's defence against infection and diseases.

3.  The blood plasm or plasma, consisting of fibrin and serum. The blood plasma is the liquid transportation for the corpuscles or cells. Serum is a fluid, freequently yellowish, and is composed of water, albumen, and various salts.

4.  Platelets, which are fragments of blood cells and essential for repairing wounds by the process of clotting.

Function of Blood

The function of the blood is this: The arterial blood in the capillaries of the body gives off its oxygen to the tissues of the body; the lymph, charged with the nutritive elements derived through the process of digestion, bathes the same tissues, by leaving the capillaries, and is collected again into lymphatic vessels, being ultimately emptied into the big veins of the body, to be mixed again with the deoxydized blood returning likewise through the veins from the capillaries of the whole body. All this exhausted blood is, together with the lymph, received into the right auricle of the heart, thence pumped through the right ventricle and the pulmonary arteries into the capillaries of the lungs, there to give up its carbonic acid, and to be charged again with oxygen. Returning through the pulmonary veins into the left auricle, and thence into the left ventricle, it is forced by the contraction of the latter into the arteries of the body to commence its circulation anew.

The lymph is a fluid like the blood-plasm, slightly yellowish or colourless and containing only white, but no red, blood-corpuscles.


Home to discover more interesting bird facts and information at The Wonder of Birds

This page ©