Blood

Functions of Blood Helps maintain homeostasis of all body organs and tissues Transportation/Distribution Oxygen from the lungs Nutrients - digestive tract  body cells Metabolic wastes  elimination sites Hormones

Functions of Blood (cont’d) Protection Prevents blood loss Clotting mechanism Prevents infection Phagocytic white blood cells (WBC) Antibodies – specialized proteins

Functions of Blood (cont’d) Regulation Body temperature by absorbing and distributing heat Acid-base balance of body fluids Buffers neutralize harmful effects of too much CO2, lactic acid, etc.

Functions of Blood (cont’d) Regulation(cont’d) Normal pH in body tissues Adequate fluid volume in the circulatory system

Blood Only fluid tissue - CT Color Slightly alkaline Temperature Varies from scarlet (oxygen rich) to dull red (oxygen poor) Slightly alkaline pH 7.35 – 7.45 Temperature 38oC or 100.4oF About 8% of body wt. Volume 5-6 L (11 pints) healthy males 4-5 L healthy females

Blood Composition Formed elements and plasma (matrix)

Plasma Liquid portion of blood 55% of blood 90% water Carry cells nutrients

Plasma (cont’d) Dissolved substances Plasma Proteins Albumin Regulates osmotic balance, pH buffering Fibrinogen Clotting of blood Globulin Defense (antibodies) and lipid transport

Plasma (cont’d) Dissolved substances(cont’d) Salts (electrolytes) - Na, K, Ca, Mg Regulates osmotic balance, pH buffering, and regulation of membrane permeability

Plasma (cont’d) Dissolved substances(cont’d) Transported substances Nutrients glucose, fatty acids, vitamins, amino acids Waste products of metabolism urea, uric acid Respiratory gases Oxygen and CO2 Hormones

Formed Elements 45% of blood Red blood cells (RBC), white blood cells (WBC), platelets

Erythrocytes RBC Most abundant formed element Transport oxygen to cells and small amounts of CO2 from cells Contain hemoglobin Iron-containing protein Actually transports oxygen Gives blood its color

Erythrocytes (cont’d) Anucleate (lack nucleus) Very few organelles Shaped like biconcave discs Flattened discs with depressed centers 4-6 million cells per mm3 of blood

Erythrocytes (cont’d) Life cycle Produced only in red marrow in bone Production regulated by special cells in kidneys (major role) and liver Release hormone erythropoietin Stimulates production of RBC

Erythrocytes (cont’d) Life cycle (cont’d) Live only about 120 days Approx. 10 billion cells die each hour Recycling Macrophages (WBC) Hemoglobin breaks down Biliverdin and bilirubin - bile pigments that color stools and urine Iron is recycled to form new hemoglobin

Leukocytes WBC Far less numerous (4,000 to 11,000 per mm3) Fight infections Only complete cells in blood May live for years Phagocytes - eat invading substances Antibodies - help destroy substances May leave the vessels – diapedesis

Types of Leukocytes Granulocytes Agranulocytes Contain granules in cytoplasm Polymorphonucleated Many shaped nuclei Agranulocytes Lack visible granules Nuclei closer to the norm

Granulocytes Neutrophils 40-70% of WBCs Phagocytic removal of foreign particles and damaged cells

Granulocyte (cont’d) Eosinophils 1-4% Phagocytic removal of allergens Kill parasitic worms

Granulocytes(cont’d) Basophils 1% or less Promotes inflammation by secreting histamine

Agranulocytes Lymphocytes 20-45% Produce antibodies for the removal of toxins and viruses

Agranulocytes (cont’d) Monocytes 4-8% Active phagocytic removal of large foreign particles and damaged cells Long-term “clean-up team”

Platelets Thrombocytes Form clots Fragments of cells Live 7 - 11 days About 300,000/mm3

Hemostasis The stoppage of bleeding following a blood vessel accident Three-step process occur in rapid sequence Blood vessel spasm Platelet plug formation Coagulation

Blood Vessel Spasm Smooth muscle in vessel cut or torn Muscle stimulated to contract Draws open ends of vessel wall together - minimizing loss This lasts less than 30 minutes Provides time for hemostatic mechanisms to take effect

Platelet Plug Formation Platelets arrive at the site of vessel breakage Increase in size; take on irregular shape with a sticky surface

Platelet Plug Formation (cont’d) Release chemicals that attract more platelets – form platelet plug Release serotonin causing vessels to constrict Normally followed by coagulation

Coagulation Conversion of fibrinogen into long threads of protein - fibrin

Coagulation (cont’d) Begins when injured vessel walls and platelets release thromboplastin which interacts with Ca ions to convert prothrombin (protein in plasma) into thrombin

Coagulation (cont’d) Thrombin works as an enzyme Combining fibrinogen elements together to form fibrin (fibers)

Coagulation (cont’d) A mass of fibrin form a netting - traps the formed elements Forms blood clot Process takes 3 to 6 minutes to complete

Coagulation (cont’d) Permanent repair begins Fibrinolysis begins - clot dissolves

Undesirable Clotting Thrombus – clot develops and persists in an unbroken blood vessel. May prevent blood flow Embolus – a thrombus breaks away and floats freely Anticoagulants – heparin, coumadin, aspirin, warfarin

Blood Groups Classified on the basis of genetically determined proteins (antigens) on RBC membranes. Complementary antibodies may or may not be present in blood. Antibodies act to agglutinate (clump) and rupture foreign RBCs. Over 30 common RBC antigens in humans.

ABO Blood Groups Blood type Antigen Antibodies Give to Receive from A A, AB O, A B Anti-A B, AB O, B AB A & B None A, B, AB, O O Anti-A & Anti-B

Rh System Antigen known as Rh - first discovered in Rhesus monkey If present = Rh-positive (85%) If not = Rh-negative (15%) Anti-Rh antibodies not naturally present in blood in Rh-neg people. Body can produce antibodies if exposed to +

Disorders Anemia - reduction in no. of RBCs or amount of hemoglobin per unit of blood Polycythemia - increase in RBCs (high blood pressure, clots, and hemorrhage)

Disorders (cont’d) Sickle cell anemia - RBCs are sickle shaped containing abnormal hemoglobin (Rarely live beyond 40). Hereditary disease.

Disorders (cont’d) Bacteremia - acute infection of the blood stream (fever, chills, skin rash) Thrombocytopenia – insufficient circulating platelets. Spontaneous bleeding. Hemophilia – several different hereditary bleeding disorders – lack of clotting factors. Partial or complete.

Disorders (cont’d) Leukocytosis - elevated number of WBCs. Indicates infection in body. Leukemia – Cancer of the blood. Bone marrow becomes cancerous. Huge no. of WBCs produced. Leukopenia – abnormally low WBC count

Disorders (cont’d) Malaria - infection of the bloodstream caused by Plasmodium (chills, fever, anemia, spleen enlargement, death). 2nd most common infectious disease in world.

Disorders (cont’d) Erythroblastosis fetalis – incompatibility between maternal (Rh-) and fetal (Rh+) blood. Baby cyanotic, anemic. Death possible, if not treated. Preventable with drug RHoGAM.

Disorders (cont’d) Hemorrhage - severe loss of blood due to injury - internal or external (Can result in shock)

Disorders (cont’d) Shock - disturbance of blood circulation reducing the blood to vital tissues Hypovolemic shock - decreased blood volume due to loss of formed elements and/or plasma Cardiogenic shock - failure of the heart Vascular shock - lowered ability of blood vessels to transport blood