T HE B LOOD

B LOOD type of connective tissue 45% is formed elements: cells and cell fragments 55% is plasma: liquid pH: 7.35 to 7.45 plasma pale yellow 91% water 7% protein 2% ions, nutrients, gases, waste fairly constant volume

F ORMED E LEMENTS OF B LOOD 95% erythrocytes (red blood cells – RBCs) 5% leukocytes (white blood cells – WBCs) and platelets hemocytoblasts = stem cells differentiate to form different types of blood cells

T YPES OF B LOOD C ELLS red blood cells composed of hemoglobin carry oxygen and CO 2 white blood cells fight infections, reduce inflammation, other immune responses platelets form platelet plugs to repair small vessels form clots to seal off wounds

W HITE B LOOD C ELLS neutrophils phagocytes increase with infections basophils release histamines to promote inflammation release heparin to prevent blood clots eosinophils reduce inflammation fight allergies and parasitic worms

W HITE B LOOD C ELLS lymphocytes produce antibodies cause allergic reactions, graft rejections, tumor control monocytes largest WBCs phagocytes increase during infections

P REVENTING B LOOD L OSS vasoconstriction – close off small vessels to reduce blood loss platelet plug – seal small break in a vessel 1. platelet adhesion to collagen in vessel wall 2. activation of other platelets 3. platelet aggregation (page 309 in book) coagulation – required for larger tears results in clot – network of fibrin that trap blood cells, platelets and fluid vitamin K – required for synthesis of clotting factors

B LOOD T ESTS blood typing A, B, AB, O, Rh+ or Rh- RBC – red blood count males: million per microliter female – 4.2 – 5.4 million per microliter hemoglobin measurement male grams per 100 mL of blood female – grams per 100 mL of blood anemia – low hemoglobin erythrocytosis – high hemoglobin

B LOOD T ESTS WBC count – white blood cell count per microliter leukocytosis – high WBC leukemia – low WBC Differential WBC neutrophils (60-70%) lymphocytes (20-25%) monocytes (3-8%) eosinophils (2-4%) basophils (0.5-1%)

B LOOD T ESTS Platelet count 250, ,000 per microliter thrombocytopenia – low platelet count

B LOOD V ESSELS arteries carry blood away from heart elastic branch into progressively smaller vessels (arterioles) capillaries where gas exchange occurs between blood and tissue fluid thinner walls than arteries and veins blood flows more slowly

B LOOD V ESSELS veins carry blood to heart thinner than arteries less elastic increase in diameter as they go toward heart increase in thickness Larger veins have valves to prevent back flow. 2 flaps like semilunar more in lower limbs varicose veins Veins dilate and cusps no longer overlap. allows backflow of blood causes edema due to increased venous pressure