Functions of Blood

1. Functions of Blood • Blood performs a number of functions: • Substance distribution • Regulation of blood levels of particular substances • Body protection

2. Blood Functions: Distribution • Blood transports: • Oxygen from the lungs and nutrients from the digestive tract • Metabolic wastes from cells to the lungs and kidneys for elimination • Hormones from endocrine glands to target organs

3. Blood Functions: Regulation • Blood maintains: • Appropriate body temperature by absorbing and distributing heat to other parts of the body • Normal pH in body tissues • Adequate fluid volume in the circulatory system

4. Blood Functions: Protection • Blood prevents blood loss by: • Activating plasma proteins and platelets • Initiating clot formation when a vessel is broken • Blood prevents infection by: • Synthesizing and utilizing antibodies • Activating complement proteins & WBCs to defend the body against foreign invaders

5. Physical Characteristics of Blood • Average volume: • 5–6 L for males; 4–5 L for females • The pH is 7.35–7.45 • Accounts for approximately 8% of body weight

6. Composition of Blood • Blood is the body’s only fluid tissue (a connective tissue) • 2 major components • Liquid = plasma (55%) • Formed elements (45%) • Erythrocytes, or red blood cells (RBCs) • Leukocytes, or white blood cells (WBCs) • Platelets – cell fragments

7. Components of Whole Blood Plasma(55% of whole blood) Buffy coat:leukocyctes and platelets(<1% of whole blood) Formed elements Erythrocytes(45% of whole blood) Withdraw blood and place in tube Centrifuge 1 2

8. Blood Plasma • Blood plasma components: • Water = 90-92% • Proteins = 6-8% • Albumins-maintain osmotic pressure of the blood • Globulins-used for transport purposes • Fibrinogen-a clotting protein • Organic nutrients – glucose, carbohydrates, amino acids • Electrolytes – sodium, potassium, calcium, chloride, bicarbonate • Non-protein nitrogenous substances – lactic acid, urea, creatine • Respiratory gases – oxygen and carbon dioxide

9. Formed Elements • Only WBCs are complete cells • RBCs have no nuclei or organelles, and platelets are just cell fragments • Most F.E. survive in the bloodstream for only a few days • Most do not divide but are renewed by cells in bone marrow

10. Erythrocytes (RBCs) • Biconcave disc • Folding increases surface area (30% more surface area) • Anucleate, no centrioles, no organelles • No cell division • No mitochondria means they generate ATP anaerobically • This prevents consumption of O2 being transported • Filled with hemoglobin (Hb) - 97% of cell contents • Hb functions in gas transport • Most numerous of the formed elements

11. Erythrocyte Function • Erythrocytes are dedicated to respiratory gas transport • Hb reversibly binds with oxygen and most oxygen in the blood is bound to Hb • Composition of Hb • A protein called globin • A heme molecule (a metal complex with iron as the central metal atom, that can bind or release molecular oxygen.) Heme groups are embedded in the hemoglobin protein,

12. Production of Erythrocytes • Hematopoiesis – blood cell formation • Occurs in the red bone marrow • Axial skeleton and girdles • Epiphyses of the humerus and femur

13. Erythrocyte Disorders • Anemia – blood has abnormally low oxygen-carrying capacity • There are many forms of anemia, each with its own cause. • Anemia can be temporary or long term, and it can range from mild to severe. • Blood oxygen levels cannot support normal metabolism • Signs/symptoms include fatigue, paleness, shortness of breath, and chills

14. Leukocytes (WBCs) • Protect the body from infectious microorganisms • Can leave capillaries • Move through tissue spaces • Many are phagocytic- that engulfs and absorbs waste material, harmful microorganisms, or other foreign bodies in the bloodstream and tissues. • Two major types of leukocytes • Granulocytes: Neutrophils, Eosinophils, Basophils • Agranulocytes: Monocytes, Lymphyocytes • Leukemia - a cancer of WBC

15. Granulocytes • Contain cytoplasmic granules that stain specifically with Wright’s stain • Are larger and usually shorter-lived than RBCs • Have lobed nuclei • Are all phagocytic cells

16. Granulocytes: Neutrophils • Account for 65-75% of total WBC’s • Neutrophils have two types of granules that: • Contain peroxidases, hydrolytic enzymes, and defensins (antibiotic-like proteins) • Neutrophils are our body’s bacteria slayers

17. Granulocytes: Eosinophils • Eosinophils account for 1–4% of WBCs • Function: • Lead the body’s counterattack against parasitic infections • Lessen the severity of allergies by phagocytizing immune complexes (ending allergic reactions)

18. Granulocytes: Basophils • Account for 0.5-1% of all WBCs • Have large, purplish-black granules that contain histamine • Histamine – inflammatory chemical that acts as a vasodilator and attracts other WBCs (antihistamines counter this effect)

19. Agranulocytes: Lymphocytes • Account for 20-25% or more of WBCs and: • Found mostly in lymphoid tissue (some circulate in the blood) • Most important cells of the immune system • Involved in graph rejection, fighting tumors and viruses • There are two types of lymphocytes: T cells and B cells • T cells - attack foreign cells directly • B cells give rise to plasma cells, which produce antibodies

20. Monocytes • Account for 3–7% of leukocytes • They are the largest leukocytes • They have purple-staining, U- or kidney-shaped nuclei • They leave the circulation, enter tissue, and differentiate into macrophages • Increase in # during chronic infections.

21. Platelets • Platelets are fragments of megakaryocytes • Platelets function in the clotting mechanism by forming a temporary plug that helps seal breaks in blood vessels. Platelet

22. Human Blood Groups • RBC membranes have glycoprotein antigens on their external surfaces • These antigens are: • Unique to the individual • Recognized as foreign if transfused into another individual • Promoters of agglutination and are referred to as agglutinogens • Presence or absence of these antigens is used to classify blood groups

23. ABO Blood Groups • The ABO blood groups consists of: • Two antigens (A and B) on the surface of the RBCs • Two antibodies in the plasma (anti-A and anti-B) • An individual with ABO blood may have various types of antigens and spontaneously preformed antibodies • Agglutinogens (antigens) and their corresponding antibodies cannot be mixed without serious reactions

24. Group A – has only the A antigen on red cells (and B antibody in the plasma) Group B – has only the B antigen on red cells (and A antibody in the plasma) Group AB – has both A and B antigens on red cells (but neither A nor B antibody in the plasma) Group O – has neither A nor B antigens on red cells (but both A and B antibody are in the plasma) • The universal red cell donor has Type O negative blood type. • The universal plasma donor has Type AB positive blood type.

25. Transfusion Reactions • Transfusion reactions occur when mismatched blood is infused • Donor’s cells are attacked by the recipient’s plasma agglutinins causing: • Diminished oxygen-carrying capacity • Clumped cells that impede blood flow • Ruptured RBCs that release free hemoglobin into the bloodstream • Circulating hemoglobin precipitates in the kidneys and causes renal failure