Red Blood Cells

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Animal Cells Red Blood Cells Red Blood Cells (RBCs) are also known as erythrocytes. There are up to 4.2 - 6.2 million RBCs in a cubic millimetre of blood. They specialize in transporting oxygen around the body. As a result of this RBCs are small and have a biconcave shape to increase their surface are to optimize the amount of oxygen that diffuses across their cell membrane. As well as this RBCs have no organelles other than a cell membrane and cytoskeleton (in mammalian RBCs). After oxygen diffuses from the alveoli of the lung into the RBC, it attaches itself to the main protein in RBCs, haemoglobin, forming bright red oxyhaemoglobin. The RBCs then travel around the body in the blood and gives oxygen to the other cells of the body. While this occurs, carbon dioxide attaches itself to the haemoglobin in the RBCs, forming blue deoxyhaemogobin. The RBCs consequently release the carbon dioxide into the lungs, which release into the air, and repeat this process. RBCs are formed in a process known as erythropoiesis. This process occurs in the red bone marrow and is constantly producing new RBCs. Erythropoiesis involves the differentiation of hemocytoblasts into erythroblasts which is stimulated by a hormone produced in the kidney known as erythropoietin. This hormone is only released when the kidney detects that there is an insufficient amount of oxygen in the blood. Erythroblasts then fill themselves with haemoglobin and then extrude their nucleus to form reticulocytes. Even though they do not have a nucleus, reticulocytes still have some endoplasmic reticulum (ER). These cells loose the ER when they are in circulation and become RBCs. The RBCs are needed to replace old RBCs that have a lifespan of 120 days. Their membranes... ... middle of paper ...
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