Normal structure and function

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Normal structure and function:

Blood accounts for about 8% of body weight. Function is to transport oxygen from lungs to all body tissues; transport nutrients from digestive tract; transport waste products to elimination sites (lungs, kidneys); transport hormones to target organs; help maintain body temperature; help maintain body pH; prevent infection

Plasma:
Straw coloured liquid – 90% is water – rest is >100 dissolved substances. Plasma proteins account for 8% of weight – albumin accounts for 60% of these

Cells:
Erythrocytes/red blood cells:
• shaped like flattened/biconcave disc with depressed centre – shape is maintained by net of fibrous proteins (spectrin) – flexible enough to allow for cell to changes shape (eg to pass through capillaries)
• consists mostly of haemoglobin – globin (protein) bound to haeme
• bound by plasma membrane, but have no nucleus
• function is transport of oxygen and carbon dioxide

Erythropoiesis:
• process of formation of erythrocytes in red bone marrow
• takes 5-7 days
• begin as haemoblasts  proerythroblast  erythroblast  normoblast  reticulocyte
• enhances by erythropoietin and testosterone

Life span of 100-120 days  removed by macrophages of liver and spleen. The released iron from the haemoglobin is reused

Thrombocytes/platelets:
Not strictly cells – they are cytoplasmic fragments of megakaryocytes
Formation s regulated by thrombopoietin

Leuckocytes/White blood cells:
Granulocytes:
• Neutrophils (multilobed nucleated cell  often called polymorphonuclear leuckocytes (PMNs); >50% of leuckocytes; phagocytose bacteria after being chemically attracted to site of inflammation)
• Eosinophils (nucleated bilobed cell with red cytoplasmic granules (filled with lysosome); 1-4% of leukocytes; function to destroy antigen-antibody complexes and act against parasitic worms)
• Basophils (nucleated cell with large blue-purple cytoplasmic granules; 0.5% of leuckocytes; function to release histamine and other inflammatory mediators)

Agranulocytes:
• Monocytes (‘U’ or kidney shaped cell with grey-blue cytoplasm; develop into macrophages in tissues  phagocytosis)
• Lymphocytes (nucleated spherical cells with pale blue cytoplasm; immune function)

Bone marrow:

Spleen:

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