The Cardiovascular System: Blood

I. Overview of the Composition of Blood: The Hematocrit Blood = vehicle for transport Average blood volume Women = 5.0 L Men = 5.5 L Components of blood Plasma Erythrocytes Leukocytes Platelets Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Hematocrit Figure 15.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

II. Plasma 90% water 6–8% proteins Electrolytes Relatively high concentrations of Na+ and Cl- Relatively low concentrations of H+, HCO3-, K+, and Ca2+ Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Components of Plasma Table 15.1 (1 of 2) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Components of Plasma Table 15.1 (2 of 2) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

III. Erythrocytes Oxygen and carbon dioxide transport Life cycle of erythrocytes Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Hemoglobin Molecule Figure 15.3 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Hemoglobin Molecule Molecule = globin + 4 heme groups Globin = 4 chains of polypeptides Heme = an iron containing group Greatly increases O2 transport 98.5% of transported O2 is bound to Hb 1.5% of transported O2 is dissolved in plasma Also binds to CO2, H+, and CO Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Life Cycle of Erythrocyte No DNA, RNA, or organelles No division of mature RBCs Short life span = 120 days Replace 2–3 million RBCs/second = 200 billion/day Synthesized in red bone marrow Erythropoiesis Filtered by spleen (and liver) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Erythrocyte Production Erythrocytes and leukocytes develop from same stem cells in bone marrow Hematopoietic stem cells Erythrocyte synthesis stimulated by erythropoietin Secreted from kidneys under conditions of low oxygen levels in blood flowing to kidneys Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Cell and Platelet Production Figure 15.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Erythrocyte Lifecycle Figure 15.4 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Table 15.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Classification of Leukocytes Granulocytes—cytoplasmic granules Neutrophils—red and blue staining granules Eosinophils—red staining granules Basophils—blue staining granules Agranulocytes—no cytoplasmic granules Monocytes Lymphocytes Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Neutrophil 50–80% of leukocytes in blood Phagocyte Circulate in blood 7–10 hours Migrate to tissues for a few days Numbers increase during infections Table 15.3 (1 of 5) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Eosinophil 1–4% of leukocytes Phagocytes (but not main mechanism of action) Defend against parasitic invaders (e.g., parasitic worms) Granules contain toxic molecules that attack parasites Table 15.3 (2 of 5) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Basophil <1% of leukocytes Non-phagocytic May defend against large parasites by releasing toxic substances Contribute to allergic reactions Histamine Heparin Table 15.3 (3 of 5) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Monocyte 5% of leukocytes Phagocytes New monocytes circulate in blood few hours Migrate to tissues and become macrophages Wandering macrophages Fixed macrophages Table 15.3 (4 of 5) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Lymphocyte 30% of leukocytes 99% of interstitial fluid cells Three types B lymphocytes (B cells) T lymphocytes (T cells) Null cells Table 15.3 (5 of 5) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

B Cells B cells associated with antibodies B cell contacts antigen  plasma cell Plasma cell secretes antibodies (immunoglobulins) Antibodies mark invaders for destruction Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

T Cells Directly damage foreign cells T cells contact infected, mutant or transplanted cells Develop into cytotoxic T cells that destroy target cell Takes several days Secretory products form pores in target cell membrane Lysis Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Null Cells Most are natural killer cells Important against viral infections Attack virus-infected cells—cause lysis Fast acting—early immune response Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Cell and Platelet Production Figure 15.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Platelets Cytoplasmic fragments derived from megakaryocytes, also called thrombocytes Figure 15.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Platelet Components Colorless Cell fragments No nucleus Has organelles and granules 100,000 – 500,000 / mL blood Important in blood clotting Granules containing secretory products Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Platelet Secretory Products ADP Serotonin Epinephrine Chemicals for blood coagulation Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Platelets Are Sometimes Sticky Platelets can adhere to surfaces under certain circumstances Adhere to damaged blood vessel walls Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Formation of a Platelet Plug Figure 15.6a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Preventing the Spread of a Platelet Plug Chemicals that prevent platelet aggregation Prostacyclin (PGI2) Produced in healthy endothelial cells Nitric oxide Released by healthy endothelial cells Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Preventing a Platelet Plug Figure 15.6b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Formation of a Blood Clot Figure 15.8 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Coagulation Pathways Figure 15.9 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Clotting Factors Clotting factors produced by liver Secreted into blood in inactive form Activated during cascade Plasma without clotting factors = serum Hemophilia = genetic disorder, deficiency in clotting factor, usually Factor VIII Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Also Necessary for Clot Formation Calcium (factor IV) Platelet factor 3 (PF3) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Factors Limiting Clot Formation Anticoagulants Proteins in plasma and surface of endothelial cells Tissue factor pathway inhibitor Secreted by healthy endothelial cells Inhibits extrinsic pathway Thrombomodulin Binds to thrombin, forming complex that activates protein C Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Requires another cascade initiated by exposure of collagen Dissolving Clot Requires another cascade initiated by exposure of collagen Plasminogen Plasmin Dissolves Clot plasminogen activators Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Plasminogen Activators Convert plasminogen to plasmin Example: Tissue plasminogen activator Secreted by endothelial cells during clot formation Activated by fibrin Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Role of Coagulation Factors in Clot Formation Disorders Hemophilia Genetic disorder caused by deficiency of gene for specific coagulation factor Von Willebrand’s disease Reduced levels of vWf Decreases platelet plug formation Vitamin K deficiencies Decreased synthesis of clotting factors Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Aspirin as an Anticoagulant Low doses—anticoagulant Inhibits formation of thromboxane A2 High doses Inhibits formation of prostacyclin Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.