Chapter 17 – Blood

1. Chapter 17 – Blood

2. Functions of blood • Transportation/distribution • Oxygen, carbon dioxide, nutrients, waste products, hormones • Regulation/homeostasis • Body temperature, pH, fluid volume • Protection • Clotting • Fights infection

3. Blood • Classified as connective tissue • Large extracellular matrix (plasma) approx 55% • Formed elements approx 45% • Color • Due to hemoglobin in red blood cells • Bright red = oxygen-rich; dark brick red = oxygen-poor • pH • Slightly alkaline 7.35 – 7.45 • Volume • Approx 8% of body weight • Males – 5-6 L • Females – 4-5 L

4. Whole blood composition

5. Formed elements • Are created in red bone marrow (hematopoiesis or hemopoiesis) from stem cells • Erythrocytes (red blood cells) • Leukocytes (white blood cells) • Only type that are true cells • Thrombocytes (platelets)

6. Erythrocyte structure • Biconcave discs • Allows for rapid gas diffusion • Anucleate and no organelles • Packed with hemoglobin

7. Hemoglobin structure • 4 polypeptide chains (2 alpha and 2 beta chains) • Each chain has an associated heme group • Each heme group has a central iron atom • Serves as the binding site for oxygen molecule

8. Gas exchange • In lungs • Oxygen diffuses from air sacs in lungs into blood and binds with iron in hemoglobin • Oxyhemoglobin – bright red • In body tissues • Oxygen detaches from iron to diffuse out of bloodstream • Deoxyhemoglobin – dark red • Hemoglobin also carries about 20% of carbon dioxide • Carbaminohemoglobin • CO2 binds to amino acids of globin chains

9. Erythrocyte production • Red bone marrow • Large capillaries (blood sinusoids) • Cells • Immature blood cells • Marcophages – consume debris/foreign cells • Hemocytoblast • Ability to become any bloodcell type • Once ‘committed’ it can not change pathway • Pathway • Color of cell changes from blue to pink as hemoglobin accumulates • Reticulocytes • Speckled appearance due to clumped ribosomes • In circulation approx 2 days before forming mature RBC • 1 – 2% of RBC count; indicates rate of RBC production

10. Regulation of RBC production • Erythropoietin (EPO) • Hormone produced by (mainly) kidneys and liver • Stimulates RBC production in response to low blood oxygen levels • Also in response to testosterone • Commerically available for kidney failure patients • EPO increases hematocrit (measure of % of RBCs in whole blood) • Has been abused by athletes

11. Blood Typing • Antigens or agglutinogens • Glycoproteins on the surface of RBCs that serve as identification • Antibodies or agglutinins • Will attack foreign antigens • Causes agglutination, or clumping • Small vessels can become blocked • Leads to cell destruction • Free hemoglobin in kidneys can result in acute renal failure • ABO and Rh can cause severe reactions if mismatched during a blood transfusion

12. ABO blood types

13. Rh factor • + has the Rh antigen; - does not • Rh – individuals do not have preformed antibodies against the Rh factor • Must have an exposure to the antigen in order to form antibodies against it • Rh- woman • Risk of erythroblastosisfetalis • Given Rogam during pregnancy

14. Erythroblastosisfetalis

15. Leukocytes • Involved with immunity • Diapedesis – WBCs can leave bloodstream and enter the lymphatic system and loose connective tissue • Amoeboid movement • Types • Granulocytes – cytoplasm contains obvious granules • Neutrophil • Eosinophil • Basophil • Angranulocytes – cytoplasm does not contain granules • Monocyte • Lymphocyte

16. Granulocytes • Neutrophil • Nucleus is multilobed • Also called polymorphonuclear leukocytes (PMNs) • Phagocytize bacteria • Eosinophil • Fight parasites that are too large for phagocytosis • Release enzymes that digest parasite • Basophil • Histamine – allergic reactions • Vasodilator; attracts other WBCs • Heparin – antocoagulant

17. Agranulocytes • Monocytes • Enters tissues to become macrophages • Fight viral infections, chronic infections, bacterial-infected cells • Lymphocytes • Most are located within the lymphatic system • T cells • Destroy infected cells and tumor cells • B cells • Plasma cells produce antibodies • Fight ‘free’ infectious agents (haven’t entered a cell yet)

18. Leukocyte production • Relative amount of WBCS • “Never Let Mom Eat Beans” • Lifespan = less than 10 days • Stem cell lines • Hemocytoblast differentiates into either: • Lymphoid stem cell line • Develops into lymphocytes • Myeloid stem cell line • Develops into all formed elements of blood except lymphocytes

19. Thrombocyte (platelet) production • Stimulated by thrombopoietin (produced by kidneys) • Megakaryocyte is formed by mitosis without cytokinesis • Megakaryocyte presses against sinusoid wall and extends cytoplasmic branches through walls into bloodstream • Break off to form platelets

20. Hemostasis • Hemostasis – stopping of bleeding • 3 stages • Vascular • Vascular spasm • Endothelial damage exposes underlying collagen • Smooth muscle contraction; endothelium becomes sticky • Platelet • Platelets adhere to endothelium and each other to form a plug • Coagulation • Clotting cascade ultimately forms fibers • Clot retraction • Platelets contract – brings damaged regions closer together for repair

22. Fibrinolysis • Clot dissolution • Plasminogen converts to plasmin • Plasminogen trapped in clot • Slow conversion • Digests fibrin strands

23. Abnormal values • Red blood cells • Anemia - low • Iron insufficiency, blood loss, kidney disease, bone marrow disorder • Polycythemia – elevated • Bone marrow disorder, dehydration • White blood cells • Leukopenia – low • Bone marrow disorder • Leukocytosis – elevated • Infection, inflammation, bone marrow disorder • Platelets • Thrombocytopenia – low • Excessive destruction or inadequate production • Thrombocytosis – elevated • Infection, inflammation, cancer