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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
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