Cardiovascular system - Blood Anatomy - Chapter20

1. Cardiovascular system - Blood Anatomy - Chapter20

2. The Cardiovascular system is comprised of the heart, blood vessels, & blood The heart acts as a “pump”, creating pressure which causes blood to move through the blood vessels of the body, allowing O2 & nutrients to be distributed to, & wastes removed from, body tissues

3. Physical characteristics of blood • Fluid connective tissue • matrix – “plasma” with dissolved proteins • cells & cell fragments – “formed elements” • temperature – 38o C • 5x more viscous than H2O • pH – 7.35-7.45

4. Functions of Blood • Transportation • O2/CO2 • nutrients/wastes • enzymes • hormones • Regulation • body temperature • pH & ion composition of interstitial fluid • intracellular fluid volume • Protection • defense against pathogens • restriction of fluid loss at injury sites

5. Composition of Blood 55% Plasma – liquid component of blood 45% Formed elements – cells/cellular fragments Erythrocytes – red blood cells (RBCs) Leukocytes – white blood cells (WBCs) Platelets – (thrombocytes)

6. Plasma

7. Formed Elements granular (B & T) agranular

8. (pluripotent stem cell) Hemopoiesis Megakaryoblast

9. Erythrocytes (RBCs) • Biconcave shape, flexible cells • around 5 million RBCs per mm3 blood • average “life span” of 120 days • Cells contains cytosol, no nucleus/organelles; filled with Hemoglobin (Hb)

10. Hemoglobin Hemoglobin allows for transport of O2 & CO2

11. As RBCs get damaged/worn out, they must be removed from circulation & replaced • About 1% of the circulating RBCs are replaced each day, at at rate of about 3 million RBCs per second • Worn out RBCs are removed by phagocytic cells in the liver, spleen & bone marrow • Most of the RBC’s hemoglobin is recycled, the pigmented part (heme) gets converted to bile pigments

12. Erythropoiesis • New RBCs are made in red bone marrow (myeloid tissue) by process of erythropoiesis • stimulus for erythropoiesis is hypoxia detected by cells of kidney

13. Leukocytes (WBCs) • More like “typical” cells with single nucleus, organelles • 5 types of WBCs characterized as granular or agranular • all function in defense • average 6000-9000 WBCs/mm3 of blood • variable “life” span depending on type of WBC- days (neutrophils) to decades (lymphocytes); in sick person, some WBCs live minutes to hours

14. Differential Count & Functions of WBCs • “WBC differential count” – normal range (in percentage) of WBCs in the peripheral circulation • differential count will vary during specific types of disorders, depending on which type of WBC responds • WBC response based on functions of specific type

15. Differential Count & Functions of WBCs • Neutrophils - 50-70% • Lymphocytes – 20-30% • Monocytes – 4-8% • Eosinophils – 2-4% • Basophils - <1% function in acute bacterial infections; phagocytic function in chronic bacterial infections; migrate into tissues to become “wandering macrophages” active against parasites & elevated in allergic reactions; destroy antibody-coated antigens by phagocytosis release chemicals (histamine, heparin) during tissue inflammation

16. Differential Count & Functions of WBCs • Lymphocytes – 20-30% Function in “immunity” – specific resistance to disease T cells- involved in “cell-mediated (aka cellular) immunity”; defense against abnormal cells & intracellular pathogens B cells- involved in “antibody-mediated (aka humoral) immunity”; defense against pathogens (Ag’s) in body fluids (blood/lymph)

17. Platelets (Thrombocytes) • Cellular fragments (cell membrane “packet” filled with cytoplasm) from large Megakaryocytes found within bone marrow • around 350,000 platelets/mm3 • platelets circulate for 9-12 days before being removed from circulation • platelets function in hemostasis– the processes that stop bleeding from damaged blood vessels – including “platelet plug formation” and “coagulation”