I. Introduction

A. Composition: plasma (fluid: 55%) and formed elements (blood cells (45%).

B. Blood Volume: 5 L/ 70 kg man.

C. Functions

1. picks up food, oxygen.

2. picks up waste from cells.

3. picks up hormones from endocrine glands.

4. transports enzymes and buffers.

5. heat regulation.

II. Blood Cells

A. Erythrocytes: red blood cells.

1. Structure

a. biconcave disks.

b. filled with hemoglobin.

2. Function: transport and exchange of oxygen and carbon dioxide.

3. Life span: 105-120 days.

4. Hemoglobin, a pigment with 4 iron molecules that picks up 4 oxygen molecules.

5. Erythropoiesis:

a. initially in yolk sac, liver, spleen; then tissue in red bone marrow.

b. erythropoeitin: hormone released from kidneys and liver to stimulate increased production of RBCs.

c. influenced by presence of vitamin B12, folic acid, used in DNA synthesis; iron for hemoglobin.

6. Anemia: low hemoglobin count or low number of volume of RBCs.

B. Leukocytes

1. Cell types

a. Granulocytes

1. neutrophils (54-62%): two or more lobed nuclei. stain pink or purple (neutral dyes). fine grains.

2. eosinophils (1-5%): two oval lobes on nuclei. stain deep red or orange. coarse granules.

3. basophils (<1%): S shaped nucleus. stain deep blue or dark purple. irregularly shaped granules.

b. Agranulocytes

1. lymphocytes (25-33%): large spherical nucleus surrounded by thin layer of cytoplasm. granules contain histamine, heparin. play role in immunity.

2. monocytes (3-9%): kidney shaped nucleus. blue gray cytoplasm.

2. Function: defense.

a. neutrophils and monocytes contain lysosomes to break down proteins and lipids. phagocytize microbes, foreign particles. neutrophils attracted to infections by inflammatory response. monocytes are mobile cells that phagocytize viral infected cells.

b. lymphocytes defend against bacteria, fungi, viruses. form antibodies.

c. eosinophils thought to function in detoxification of proteins, harmful products.

d. basophils: prevention of intravascular coagulation by releasing heparin.

3. Formation

a. Red bone marrow: neutrophils, basophils, and eosinophils, as well as RBCs and a few lymphocytes and monocytes.

b. Lymphatic tissue: lymphocytes and monocytes.

C. Thrombocytes: platelets. not complete cells.

1. Physical properties

a. agglutination: clumping

b. adhesiveness: stick to themselves and every surface contacted.

c. aggregation: group together in large masses.

2. Function

a. hemostasis: stop blood flow. platelets stick to damaged lining of injured capillary and to each other to form a plug, stopping blood flow.

b. coagulation: blood clotting. 1-5 seconds after injury to a capillary, platelets adhere to the damaged lining of the vessel and to each other. this forms a hemostatic platelet plug, which helps stop blood flow into tissues.

3. Formed in red bone marrow, lungs, spleen, by fragmentation of megakaryocytes, multilobar nuclei with bizarre shapes.

4. Life-span: 10 days

III. Blood Groups

A. Agglutination: clumping of red blood cells due to presence of agglutinogens (antigens) on RBC membranes and of agglutinins (antibodies) dissolved in plasma.

B. A, B, Rh antigens most important. "Blood type" refers to the type of antigens present on the RBC membrane.

1. Blood Types: A, B, AB, O. O is universal donor, AB is universal recipient. cross-matching is necessary, though, due to other antigens present.

2. Rh factor: + if antigen present; - if antigen not present.

C. Plasma contains antibodies to react with antigens other than own (A antigens with B antibodies).

D. Anti-Rh antibodies

1. only present if Rh- blood has come in contact with Rh+ blood. by transfusion or by pregnancy (Rh- mother carrying Rh+ baby).

2. Erythroblastosis fetalis: mother’s body forms antibodies which attack and destroy RBCs of baby. RhoGAM is a protein that stops the mother’s blood forming anti-Rh antibodies.

IV. Plasma

A. Composition: 90% water, 10% solutes. whole blood minus formed elements. solutes mostly proteins

1. albumins (6%): maintains osmotic pressure of blood. prothrombin works with fibrinogen in clotting. (55% total protein)

2. globulins (3%): transport lipids, fat soluble vitamins. gamma globulins circulate as antibodies. (38% total protein)

3. fibrinogen (1%): function in clotting. 7% total protein)

B. Functions in transporting nutrients, gases, vitamins, regulating fluid, electrolyte balances, maintaining pH.

C. Synthesis occurs in liver. diet must contain vitamin K for plasma protein synthesis.

V. Blood Coagulation

A. Plugs ruptured vessels to stop bleeding to prevent loss of vital body fluid.

B. Mechanism of Clotting

1. When blood vessel is cut or broken, muscle stimulated to contract to decrease bleeding. lasts only a few minutes, but platelets release serotonin to maintain spasm.

a. Step I

1. Thromboplastin released

a. Intrinsic system: thromboplastin is released by platelets, involving plasma factors IV, V, VII, IX, X, XI, XII.

b. Extrinsic system: thromboplastin is released by the damaged tissues, involving plasma factors IV, V, VII, X.

2. Prothrombin, a plasma protein, is converted to thrombin, a plasma enzyme, by the action of thromboplastin and calcium.

b. Step II: Fibrinogen, a soluble plasma protein, is converted to strands of fibrin, which is insoluble, by thrombin.

1. Platelets clump, adhere to injured area. disintegrate, releasing thromboplastin, triggering step one.

2. Fibrin appears as tiny, tangled threads which catch blood cells. yellowish liquid remaining: blood serum (plasma contains clotting factors)

C. To clot or not to clot

1. Conditions that hasten clotting: cuts or cholesterol plaques: clot forms on rough spot in endothelium. abnormally slow blood flow allows thromboplastin to accumulate.

2. Conditions that oppose clotting: clots do not form on smooth surface of vessel lining. presence of antithrombins, which oppose the action of thrombin, prevents clotting. Heparin acts as an antithrombin.

D. Thrombus: clot formed in vessel abnormally.

E. Embolus: dislodged or fragmented thrombus in bloodstream. can block blood flow in narrow vessels. associated with atherosclerosis.

F. Clinical Methods of Clotting

1. apply rough surface, heat; squeeze tissues gently. causes more platelets to disintegrate and release factors.

2. apply purified thrombin

3. apply fibrin foams

anatomy page