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Erythrocytes are more commonly known as red blood cells. They contain no nuclei or organelles and have a biconcave discoid shape to increase its surface area for gas exchange. They are used in oxygen transportation from lungs to tissues, and carbon dioxide transportation from tissues to lungs. Erythrocytes contain haemoglobin, which is an oxygen-carrying pigment that gives blood its red colour.
	Neutrophils are the most abundant blood leucocyte. 50% of neutrophils in blood are attatched to the walls of blood vessels. They circulate in blood for about 10 hours before migrating to tissues, where they have a lifespan of about 2 days. They are the first cells to arrive at a point of inflammation, they are transported to the site of tissue damage by chemotaxis. The cell consumes the bacteria by phagocytosis and then the bacteria is destroyed by oxygen-independent and oxygen-dependent degradation.
Basophils are the least abundant blood leucocyte and play an important role in allergic responses and also play a role in immunity against parasites. The granule contents include histamine and heparin.
	Eosinophils contain a distinct bi-lobed nucleus and are important in the response to parasitic and allergic diseases. They release their cell contents onto larger pathogens and can also undergo phagocytosis. Their products are anti-inflammatory and can inactivate mast cell products.
Monocytes circulate in the blood for approximately 8 hours before migrating into the tissues, where they differentiate into macrophages. They undergo phagocytosis and remove antigens.
	Platelets are disc-shaped, granule-containing cells that contain no nucleus. They are required for normal haemostasis by participating in blood clotting. They have a life span of up to 10 days before being destroyed in the spleen or the pulmonary vascular bed.
Lymphocytes circulate in both the blood and the lymph, they can migrate into tissue spaces and lymphoid organs. They have the longest lifespan of any of the leucocytes, up to many years and are essential in immune response where they release haemopietic substances.