University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2019
Views:

219

Pages:

10
Author:

Donavan Williams

Leukocytes (WBCs) • 4,500-10,000 white blood cells/mcl (cells per microliter) • Granulocytes contain specific granules – eosinophils - pink-orange granules and bilobed nucleus (2-4%) – basophils - abundant, dark violet granules (<1%) • large U or S-shaped nucleus hidden by granules – neutrophils - multilobed nucleus (60-70%) • Very lightly stained reddish to violet granules in cytoplasm • Agranulocytes contain no noticeable granules – lymphocytes - round, uniform dark violet nucleus (2533%) • variable amounts of bluish cytoplasm (scanty to abundant) – monocytes – indented nucleus (3-8%) • large cell with abundant cytoplasm Granulocytes • Neutrophils ( in bacterial infections) – phagocytosis of bacteria – releases antimicrobial chemicals • Eosinophils ( in parasitic infections or allergies) – phagocytosis of antigen-antibody complexes, allergens and inflammatory chemicals – release enzymes that destroy parasites such as worms • Basophils ( in inflammation or infection) – secrete histamine (vasodilator) – secrete heparin (anticoagulant) Agranulocytes • Lymphocytes ( in diverse infections and immune responses) – destroy cancer cells, foreign cells, virally infected cells – coordinate actions of other immune cells – secrete antibodies and provide immune memory – two groups: T-lymphocytes and Blymphocytes • Monocytes ( in viral infections and inflammation) – mature into macrophages that consume (phagocytosis) pathogens and debris – “present” antigens to activate other immune cells Abnormalities of Leukocyte Count • Leukopenia = low WBC count (<5000/L) – causes: radiation, poisons, infectious disease • Leukocytosis = high WBC count (>10,000/L) – causes: infection, allergy and disease • Leukemia = cancer of hemopoietic tissue – myeloid (granulocyte) or lymphoid (lymphocyte) – effects: patient subject to opportunistic infection, anemia and impaired clotting Normal and Leukemia Blood Smears Megakaryocytes and Platelets • Megakaryocytes are bone marrow cells that repeatedly replicate their DNA without dividing – megakaryocytes are gigantic cells (100 m diameter) with a huge nucleus – megakaryocytes remain in the bone marrow • Megakaryocytes release fragments that enter the bloodstream as platelets – platelets live for about 10 days – some platelets are stored in the spleen and can be released as needed Megakaryocytes & Platelets Science volume 317 21 September 2007 p. 1689 Platelets • Platelets are small fragments of megakaryocytes – platelets are only 2-4 m diameter – platelets contain granules used in clot formation – platelets have pseudopods used for phagocytosis and clot retraction • Normal Count: 130,000 to 400,000 platelets/L • Functions – secrete clotting factors, growth factors for endothelial repair, and vasoconstrictors in broken vessels – form temporary platelet plugs – attract WBCs to sites of inflammation – retract and eventually dissolve old blood clots