This is a highly specialized reddish tissue consisting of red blood cells, white blood cells and platelets suspended in a liquid inter cellular matrix called plasma. The main function of blood is to transport materials and gases, fight against diseases and the formation of dats. The many functions of blood are possible because of the various cells and fragments its contents.

1. Red blood cells or erythrocyte

• It transports respiratory gases to and forms the tissues. Their structure is greatly modified for these purpose
• The cytoplasm of a mature red blood has no nucleus and is depressed on each side giving it a biconcave shape
• The interior of the cell is filled with the red pigment hemoglobin which have a high affinity or oxygen
• The lack of nucleus and his biconcave shape enable more hemoglobin to be packed inside the cytoplasm
• Its thin elastic membrane makes it possible for oxygen to easily diffuse across and combine with hemoglobin for it to be transported.

1. White blood cells or leucocytes

• It defend the body against disease causing micro organisms the body actives defend mechanisms are carried out by two types of white blood cells
• Granulocytes have a granular cytoplasm and lobe-shape nucleus e.g. neutrophils which undergoes phagocytosis destroying bacterias
• A granulocyte have a non granular cytoplasm and a spherical nucleus e.g. lymphocytes which produce anti-bodies that neutralize the toxin produce by microbes.

1. Platelets (thrombocytes)

These are minutes cell fragments. They function in the mechanisms when a blood vessel is damage thus preventing excess lost of blood and also preventing the entering of pathogens into blood.