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Chapter 19LectureSlideswith

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Chapter 19

Cardiovascular System: Blood

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19.1 Functions of Blood1. Transport of gases, nutrients and waste products;

e.g. oxygen2. Transport of processed molecules; e.g., precursor of

vitamin D from skin to liver then kidneys3. Transport of regulatory molecules; e.g., hormones4. Regulation of pH and osmosis (normal pH of most

body tissues between 7.35 and 7.45)5. Maintenance of body temperature; e.g., warm blood

shunted to the interior of the body6. Protection against foreign substances; e.g.,

antibodies7. Clot formation

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19.2 Composition of Blood

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19.3 Plasma• Liquid part of blood.

– Colloid: liquid containing suspended substances that don’t settle out of solution

– 91% water. Remainder proteins, ions, nutrients, waste products, gases, regulatory substances

• Proteins:– Albumins: viscosity, osmotic pressure, buffer,

transports fatty acids, free bilirubin, thyroid hormones

– Globulins: transports lipids, carbohydrates, hormones, ions, antibodies, and complement

– Fibrinogen: blood clotting

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Plasma• Ions: involved in osmosis, membrane potentials,

and acid-base balance• Nutrients: glucose, amino acids, triacylglycerol,

cholesterol, vitamins• Waste Products:

– Urea, uric acid, creatinine, ammonia salts. Breakdown products of protein metabolism

– Bilirubin. Breakdown product of RBCs– Lactic acid. End product of anaerobic

respiration• Gases: oxygen, carbon dioxide, and inert nitrogen• Regulatory substances: hormones, enzymes

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19.4 Formed Elements• Red blood cells (erythrocytes). Biconcave discs,

anucleate, contain hemoglobin; transports oxygen and carbon dioxide.

• White blood cells (leukocytes)– Granulocytes: cytoplasm contains large

granules; have multi-lobed nuclei. Three distinctive types: neutrophils, eosinophils, basophils

– Agranulocytes: cytoplasm contains small granules and nuclei that are not lobed. Two distinctive types: lymphocytes and monocytes

• Platelets (thrombocytes). Cell fragment. Form platelet plugs, release chemicals necessary for blood clotting.

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Production of Formed Elements

• Hematopoiesis or hemopoiesis: Process of blood cell production

• Stem cells: All formed elements derived from single population– Proerythroblasts: Develop into red blood cells– Myeloblasts: Develop into basophils,

neutrophils, eosinophils– Lymphoblasts: Develop into lymphocytes– Monoblasts: Develop into monocytes– Megakaryoblasts: Develop into platelets

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Hematopoiesis

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Red Blood Cells

• Found in higher concentration in male than in female plasma

• Components– 1/3 Hemoglobin– 2/3 Lipids, ATP,

carbonic anhydrase

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RBC Function: Transport

• Oxygen from lungs to tissues: 98.5% attached to hemoglobin; 1.5% dissolved in plasma

• Carbon dioxide from tissues to lungs. – 7% dissolved in plasma– 23% in combination with hemoglobin– 70% transported as bicarbonate ions

produced as a result of combination of H2O and CO2 because of enzyme carbonic anhydrase found within RBCs

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Hemoglobin• Types of hemoglobin

– Embryonic and fetal: have greater attraction for oxygen than adult. Fetal production stops after birth.

– Adult • Oxyhemoglobin:

transporting oxygen• Deoxyhemoglobin• Carbaminohemoglobin:

transporting carbon dioxide

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Hemoglobin Composition

• Four globin molecules (polypeptide chains): Transport carbon dioxide (carbonic anhydrase involved), nitric oxide. NO brought from lungs to tissues, induces smooth muscles to relax, lowering BP.

• Four heme molecules, each containing one iron atom: transport oxygen

• Iron required for oxygen transport. Iron absorbed in upper small intestine; absorption increased by stomach acid and vitamin C. Iron lost in urine, feces, menstrual fluid.

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Erythropoiesis

• RBCs last 120 days in circulation (enucleated)

• Production of red blood cells– Stem cells → proerythroblasts → early erythroblasts →

intermediate erythroblasts → late erythroblasts → reticulocytes

• Erythropoietin: hormone stimulates RBC production; produced by kidneys in response to low blood O2 levels.

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Erythropoiesis

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Hemoglobin Breakdown

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White Blood Cells

• Protect body against microorganisms and remove dead cells and debris

• Movements– Ameboid: pseudopods

– Diapedesis: cells become thin, elongate and move either between or through endothelial cells of capillaries

– Chemotaxis: attraction to and movement toward foreign materials or damaged cells. Accumulation of dead white cells and bacteria is pus.

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Formed Elements/WBC

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• Neutrophils: after leaving bone marrow, stay in circulation 10-12 hours then move into other tissues. Become motile, phagocytize bacteria, antigen-antibody complexes and other foreign matter. Secrete lysozyme. Last 1-2 days. Account for 60-70% of the WBC.

• Eosinophils. Leave circulation and enter tissues during inflammatory response. Prevalent in allergic reactions. Destroy inflammatory chemicals like histamine. Release chemicals that help destroy tapeworms, flukes, pinworms, and hookworms. Account for 2-4% of the WBC.

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•Basophils: least common. Leave circulation and migrate through tissues, play a role in both inflammatory response and allergic reactions. Produce histamine and heparin. Account for less than 1% of the WBC.

•Lymphocytes: produced in red bone marrow but then migrate to lymphatic tissues and proliferate. Responsible for antibody production. Studied extensively with the immune system. Account for 20-25% of the WBC.

•Monocytes: remain in circulation for 3 days, leave circulation and become macrophages. Phagocytic cells. Can break down antigens and present them to lymphocytes for recognition. Account for 3-8% of the WBC.

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Platelets

• Cell fragments pinched off from megakaryocytes in red bone marrow

• Surface glycoproteins and proteins allow adhesion to other molecules; i.e., collagen

• Important in preventing blood loss– Platelet plugs

– Promoting formation and contraction of clots

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19.5 Hemostasis

• Arrest of bleeding

• Events preventing excessive blood loss– Vascular spasm: Vasoconstriction of damaged

blood vessels. Can occlude small vessels. Caused by thromboxanes from platelets and endothelin from damaged endothelial cells.

– Platelet plug formation – Coagulation or blood clotting

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Platelet Plug Formation

* Also expression of coagulation factor V and phospholipid (platelet factor III). Important for coagulation

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Coagulation• Stages

– Activation of prothrombinase– Conversion of prothrombin to

thrombin– Conversion of fibrinogen to

fibrin• Coagulation factors.

– Proteins found in plasma. – Circulate in inactive state until

tissues are injured. – Damaged tissues and platelets

produce chemicals that begin activation of the factors.

• Pathways– Extrinsic– Intrinsic

• Result: blood clot. A network of threadlike fibrin fibers, trapped blood cells, platelets and fluid

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Clot Formation

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Extrinsic Clotting Pathway

• Begins with chemicals outside of blood• Stage 1

– Damaged tissues release tissue factor (TF; factor III)– When Ca2+ is present, forms complex with factor VII,

activating factor X– Prothrombinase is formed

• Stage 2: prothrombinase converts prothrombin into thrombin

• Stage 3– Thrombin converts fibrinogen to fibrin– Thrombin activates factor XIII, which stabilizes clot

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Intrinsic Clotting Pathway

• Begins with chemicals that are part of the blood• Stage 1

– In damaged blood vessels, factor XII comes in contact with exposed collagen, activating factor XII

– Stimulates factor XI, activates factor IX

– Activated factor IX joins with factor VIII, platelet phospholipids and Ca2+ to activate factor X

– Prothrombinase is formed

• Stages 2 and 3 progress to clot formation

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Control of Clot Formation• Anticoagulants: prevent coagulation factors from

initiating clot formation. • Coagulation occurs when coagulation factor

concentration exceeds a given threshold. At site of injury, threshold is exceeded.

• Anticoagulants– Antithrombin: produced by liver, slowly inactivates

thrombin– Heparin: produced by basophils and endothelial cells.

Increases effectiveness of antithrombin– Prostacyclin: prostaglandin derivate from endothelial

cells. Causes vasodilation and inhibits release of coagulating factors from platelets

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Fibrinolysis

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19.6 Blood Grouping

• Transfusion: transfer of blood or blood components from one individual to another

• Infusion: introduction of fluid other than blood

• Determined by antigens (agglutinogens) on surface of RBCs

• Antibodies (agglutinins) can bind to RBC antigens, resulting in agglutination (clumping) or hemolysis (rupture) of RBCs

• Groups: ABO and Rh

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ABO Blood Group

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Agglutination Reaction

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Transfusion

• Type A blood has anti-B antibodies; Type B blood has anti-A antibodies

• Suggested that these antibodies are present because of exposure to A and B antigens on bacteria and food

• Donor: gives blood. Recipient: receives blood• Type O as “universal donor”. Can actually cause

transfusion reactions because of antibodies in O blood plasma

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Rh Blood Group

• First studied in rhesus monkeys• Types

– Rh positive: Have these antigens present on surface of RBCs– Rh negative: Do not have these antigens present

• Hemolytic disease of the newborn (HDN)– Rh positive fetus, Rh negative mother.– Late in pregnancy, Rh antigens of fetus cross placenta (through a

tear in placenta or during delivery); mother creates antiRh antibodies (primary response)

– Second Rh positive pregnancy might initiate secondary response and HDN (potentially fatal to fetus since antibodies to its RBCs would cross the placenta from the mother to the fetus, destroying fetal RBCs).

– Injection of RhoGAM. Contains antibodies against Rh antigens. Antibodies attach to any fetal RBCs and they are destroyed.

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Erythroblastosis Fetalis

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19.7 Diagnostic Blood Tests• Type and Crossmatch: determination of ABO and

Rh blood types. Red cells tested against antibodies• Complete Blood Count

– Red Blood Count: number of RBCs/ microliter of blood– Hemoglobin Measurement: grams of hemoglobin/100

mL of blood. For a male, 14-18, female 12-16 g/100 mL– Hematocrit Measurement: percent of blood that is RBCs– White Blood Cell Count: 5,000-10,000 /microliter of

blood

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Hematocrit

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• Differential White Blood Count: determines percentage of each of the five types of WBC– Neutrophils: 60-70%– Lymphocytes: 20-30%– Monocytes: 2-8%– Eosinophils: 1-4%– Basophils: 0.5-1%

• Clotting– Platelet Count: 250,000- 400,000/microliter– Prothrombin Time Measurement: measures how long it

takes for blood to start clotting. 9-12 seconds. To test, thromboplastin is added to whole plasma

• Blood Chemistry: composition of materials dissolved or suspended in the plasma. Used to assess functioning of many body systems