Fifth lecture
2-White blood cells Nucleated cells. larger than RBC’s. Approx. 1 x 1010 per liter. Involved in defense against pathogens. Can move through capillary wall to act locally at site of infection. Attracted to trauma site by chemotaxis.
2-White blood cells Agranulocytes Granuloyctes Lymphocytes Monocytes Neutrophils Basophils T Cells B Cells Eosinophils Killer T Cells Helper T Cells
2-Leukocytes (WBCs) Part of defense system: Protect against bacteria, viruses, parasites Attracted to sites of infection. Diapedesis & chemotaxis: leave capillary by squeezing between endothelial cells. Ameboid movement: Travel toward infection Originate in bone marrow. They are classified into: A-Granulocytes B-A granulocytes
Diapedesis
Granulocytes WBCs with granules in cytoplasm Neutrophils Eosinophils Visible with LM Neutrophils Eosinophils Basophils Phagocytic Larger than RBCs Lobed nuclei
Formation of granulocytes Promyelocytes Eosinophilc myelocytes Neutrophilic myelocytes Basophilic myelocytes basophils eosinophils neutrophils It takes about 10 days for the mature WBC’s to from the precursor cells at which they are released into the circulation. Colony Stimulating Factors govern the rate of WBC synthesis.
Neutrophils 60% of WBCs. half-life of 6 hours so need to produce 100 billion per day for normal function! Lobed nucleus. Light staining granules. Digestive enzymes. Function Phagocytize & destroy bacteria. First cells to respond to infection. Secrete antibacterial chemicals. Phagocytize & digest bacteria.
Eosinophils 1-4% of WBCs. Lobed nucleus. Eosin-staining granules. Phagocytize allergen-Ab complexes. increased following allergic response. Attack parasites.
Basophils 0.5% of WBCs. Lobed nucleus. Large granules stained dark purple. Release histamine and heparin. Trigger inflammation.
Lymphocytes A granulocyte 20-45% of WBCs Spherical, dark-staining nucleus Thin rim of blue staining cytoplasm Each lymphocyte recognizes and acts against a specific antigen
Lymphocytes Derived from lymphoblasts which divide a number of times to form pro-lymphocytes. Pro-lymphocytes mature into B or T lymphocytes in lymphoid tissue i.e. thymus, spleen T lymphocytes can attack foreign cells directly. B lymphocytes transform into plasma cells and secrete antibodies.
Monocytes A granulocyte 4-8% of WBCs Horseshoe shaped nucleus. originate from monoblasts. Life span 72 hours, after which they migrate to connective tissue where they remain for up to 3 months. Migrate to spleen, liver, lungs and lymph nodes where they phagocytose invading pathogens and are termed macrophages.
3-Platelets (thrombocytes) Not strictly speaking cells. Really membrane bound cell fragments budded off of bone marrow cells and released in to circulation. Rarely nucleated and only 2-4m in diameter. Life span 10 days.
3-Platelets (thrombocytes) Adhere to damaged vessel walls and exposed connective tissue to mediate blood clotting. DO NOT adhere to healthy intact endothelium. Fragments of megakaryocytes in bone marrow. Attracted to damaged places.