Blood Composition and Function

Blood Composition & Function

Blood - The River of Life· connective tissue

formed elements - living blood cellsplasma - non-living fluid matrixdissolved fibrous proteins (responsible

for blood clotting)· blood sample

top - plasma (55%)middle - buffy coat (white blood cells and platelets)bottom - erythrocytes, or hematocrit (45%)

· metallic, salty taste· pH 7.35 to 7.45 (slightly alkaline)· 38 C or 100.4 F (slightly warmer than body temp)· accounts for 8% of our body weight· average volume

males - 5-6 L (about 1.5 gallons)females - 4-5 L

Blood Functions· DISTRIBUTION

1. deliver oxygen from lungs and nutrients from digestive tract to all body cells

2. transport metabolic waste products from cells to elimination sites (lungs, kidneys)

3. transport hormones from glands to target organs· REGULATION

4. maintain appropriate body temperature5. maintain normal pH in body tissues6. maintain adequate fluid volume in circulatory

system· PROTECTION

7. prevent blood loss (clotting)8. prevent infection (antibodies, complement

proteins, white blood cells)

Blood Plasma· straw-colored, sticky fluid· about 90% water· 8% plasma proteins

albumin (60%) - transports molecules, blood buffer, contributes to plasma osmotic pressure (keeping water in blood)

globulin (36%) - transports molecules (alpha and beta), antibodies (gamma)

fibrinogen (4%) - blood clotting· 2 % other

nutrients, electrolytes, respiratory gases, hormones

Formed Elements

erythrocytes

leukocytes

red blood cell (RBC)

white blood cell (WBC)

cell fragments

platelets· produced in red bone marrow

Erythrocytes - RBC· small, biconcave discs· mature RBCs lack a nucleus· contains hemoglobin (gas transport)

oxygen-rich - scarletoxygen-poor - dark red

· structure supports their function1. small size and biconcave shape increase

surface area2. 97% hemoglobin3. generate ATP through anaerobic

respiration, so they do not consume the oxygen they carry· live about 120 days before destroyed· 4.3-5.8 million per microliter

Blood Composition and Function

Erythrocyte Function· gas (O2 and CO2) transport· hemoglobin binds easily and reversibly with O2

globin - protein containing 4 polypeptide chainsheme - red pigment containing an iron atom

found in each polypeptide chain· each hemoglobin can carry 4 O2 atoms· each RBC contains 250 million hemoglobin molecules

can carry 1 BILLION oxygen atoms· hemoglobin

oxyhemoglobin - O2 attached to iron (bright red)

deoxyhemoglobin - O2 detaches from iron (dark red)

carbaminohemoglobin - CO2 combined with globin's amino acids

Hematopoiesis· blood cell formation· occurs in red bone marrow· hemocytoblasts (blood cell builders) - stem cells that differentiate into myeloid and lymphoid cells

myeloid - RBCs, platelets, basophils, eosinophils, monocytes, and neutrophils

lymphoid - lymphocytes

EPO & Negative Feedback· make 2 RBC million/sec· controlled by erythropoietin (EPO), a hormone· negative feedback

tissue O2 levels decrease kidneys release EPO stimulates red bone marrow to make RBCs

RBC count increases tissue O2 levels increase

Blood Doping

Leukocytes - WBC· 4,800-10,800 per microliter· NO hemoglobin (appear white)· live a few days to several years· defend body against foreign invaders· granulocytes

neutrophils - most numerous, polymorphonuclear, first to respond to infections, phagocytes

eosinophils - two-lobed nucleus, granules pick up red stain (eosin), attack parasitic worms

basophils - rarest, granules pick up blue (basic), stain, U-shaped nucleus, release histamine· agranulocytes lymphocytes - large, purple nucleus, B or T, involved in immunity

monocytes - largest leukocyte, U-shaped nucleus, macrophages

Platelets· aka thrombocytes· no nucleus· about half the size of RBC· live about 10 days· 150,000-400,000 per microliter· pieces of megakaryocytes· important in initiating the blood clotting process