Hematopoiesis and Blood Clotting Anatomy and Physiology

Hematopoiesis Blood cell formation Occurs in red marrow (myeliod tissue) Skull and pelvis Ribs Sternum Proximal epiphyses humerus and femur One ounce/day (1 billion cells)

Cell Formation All arise from hemocytoblast Once it starts type is committed Second generation Lymphoid stem cell (lymphocytes) Myeloid stem cell (all other formed elements)

RBC Formation Anucleate so they don’t grow or divide Last between 100-120 days Remains removed in spleen, liver, etc Cell division in red marrow replaces them When mature nucleus & organelles ejected Creates reticulocyte (immature) 2 days to mature 3-5 total

RBC Homeostasis Controlled by hormone erythropoietin Produced mainly in the kidney O2 levels determine levels not number of cells!

Formation of WBC’s and Platelets Also hormonally controlled WBC’s Colony stimulating factors (CSF’s) Interleukins Platelets thrombopoietin

Hemostasis Blood standing still Fast and localized Uses many substances normally in the blood and a few others Vascular spasms Platelet plug formation Coagulation Fibrous tissue seal

Hemostasis 1. Vascular Spasm Vasoconstriction Decreases blood flow Direct injury Pain receptors Serotonin release 2. Platelet Plug Formation Stick to collagen Release serotonin

Continued Coagulation Injured tissue release TF PF3 reacts with TF, vitamin K and clotting factors and Ca2+ Triggers cascade Clot retracts bringing edges together

Clotting Information 3-6 minutes Cascade deactivated rapidly to keep the clotting localized Clot is broken down when tissue heals How do we help clotting along? Pressure Gauze

Homeostatic Imbalance Thrombus (stationary clot) Embolus (moving clot) Caused by rough endothelium Fatty deposits Slow blood flow Prevented by Aspirin Heparin Dicumarol (Coumadin)

Bleeding Disorders Thrombocytopenia Liver problems Hemophilia Low platelets May cause petichiae (small purple blotches) Liver problems Low vitamin K Hepatitis/Cirrhosis Hemophilia Hereditary lack of clotting factors Fresh plasma or pure clotting factors AIDS linked to blood products in past