TRANSPORT IN MAMMALS
Blood is a connective tissue and every connective tissue consists of cell, ground substance or matrix and fibres. For blood, it has cells, matrix in the form of plasma and fibres in the form of fibrin. In transportation, the surface area to the volume ratio of organisms contributes to the rate of movement of materials. For example in Hydra, and flat worms, the ratio is so high so simple diffusion can allow substances to reach all tissues easily. If the ratio is low, in mechanisms to carry materials to all parts of the body. This is the reason for special transport system such as blood circulatory system. The pH of blood is 7.
COMPOSITION OF BLOOD
The mammalian blood is composed of red blood cells, white blood cells, platelets, plasma and serum. RED BLOOD CELLS (ERYTHROCYTES)
They are biconcave discs, numbering on average between 4.5 to 5 million per millimeter of blood. They are produced in the marrow of all bones. In adults the sternum, scapulae, ribs and pelvic also produce the red blood cells. In the foetus, they are produced by the liver. The red blood cells are not true-cells because they lack nucleus. The red blood cell has an iron containing substance called haemoglobin. It readily combines with either oxygen or carbon dioxide. When it combines with carbon dioxide it is called carboxyhaemglobin. However the red blood cells of the foetus contain myoglobin which has higher affinity for oxygen than haemoglobin. The red blood cells transport carbon dioxide in the form of weak carbonic acid. The enzyme for the reaction is carbonic anhydrate. The life span of the red blood cells is about 120 days. When they die they are stored in the gall bladder of the liver as bile. WHITE BLOOD CELLS (LEUCOCYTES)
They are larger than red blood cells. They have nuclei but no haemoglobin in their cytoplasm. They are produced in the red bone marrow and the lymph. The ratio of the red blood cells is 600:1. There are 2 kinds of white blood cells:...
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