Anatomy Chapter 10 - Blood

Composition and Function of Blood Blood is the “river of life”, it transports everything that must be carried within the body – nutrients, wastes, gases. Blood is the only fluid tissue – a connective tissue in which living blood cells are suspended in a matrix called plasma. Erythrocytes Leucocytes Platelets Buffy coat Plasma

Physical Characteristics of Blood Blood is a sticky opaque fluid with a metallic taste; salty taste Color depends on the oxygen content – scarlet to dull red Blood is heavier than water; five times more viscous because of formed elements Slightly alkaline with a pH of 7.35 – 7.45 Temperature averages 38* C / 100* F Blood makes up 8% of your body weight; 5 to 6 liters (6 quarts) in males and 4 to 7 liter in females Blood Smear Photomicrograph of blood

Plasma – 90% water – liquid portion >100 dissolved substances (nutrients, salts, gases, plasma proteins, wastes) Plasma proteins are the most abundant solutes in plasma albumin – contributes to osmotic pressure of the blood, keeps water in the bloodstream clotting proteins help stem blood loss antibodies protect the body from pathogens The exact composition of blood varies continuously. Our body adds and removes substances, keeping the composition within homeostatic ranges. The liver, kidneys, and respiratory system maintain proper protein and pH ranges.

Formed Elements – Table 10.2 p. 333 Less numerous, bodies defense against disease: Erythropoiesis – erythrocyte production

Leukocytosis – high WBC count, indication of bacterial or viral infection. Leukopenia – abnormally low count, side effect of certain drugs.

Hematopoiesis - blood cell formation; red bone marrow Hemocytoblast stem cells – all formed elements arise from these stem cells. These cells reside in the bone marrow and form two types of descendents – lymphoid stem cells and myeloid stem cells. Myeloid stem cells – produce all the classes of formed elements except lymphocytes. The development of blood cells. Erythropoietin – a hormone that controls the rate of erythrocyte production. Colony stimulating factors (CSF) – stimulates the formation of leukocytes and platelets. Thrombopoietin – accelerates the production of platelets.

Hemostasis - the series of reactions set in motion to stop the flow of blood when the wall of a blood vessel breaks. These reactions are fast and localized. Platelet plug formation Vascular Spasms Coagulation Events occur Tissue factor PF3 Prothrombin Activator Fibrinogen Disorders of Hemostasis: Thrombus Embolus Thrombocytopenia Hemophilia

Human Blood Groups and Transfusions The loss of 15 - 30% of your blood leads to pallor and weakness. The loss of over 30% can cause severe shock and be fatal. Whole blood transfusions are given to replace substantial blood loss and treat severe anemia and thrombocytopenia. Blood can be stored at 39.2* for about 35 days if needed. Hospital Blood Usage: 18% Leukemia , bone marrow and cancer 15% Gastrointestinal blood loss 15% Hereditary, nutritional / other anemias 14% Orthopedic and Urologic Surgery 13% Other surgery 12% Trauma 11% Cardiac 4% Obstetrics/ Gynecological

Human Blood Groups AB blood type is the universal recipient. The plasma membrane of RBC’s have genetically determined proteins called antigens. Our bodies recognize these as foreign. If the wrong type of blood is introduced into the body, the immune system would be stimulated to release antibodies and mount a defense against the foreign blood. RBC’s would clump or agglutinate leading to clotting of small vessels throughout the body. This can be lethal. AB blood type is the universal recipient. O blood type is the universal donor.

Rh Blood Groups Rh blood groups are named because of 1 of 8 Rh antigens identified in Rhesus monkeys. Most Americans are Rh +, their RBC’s carry the Rh antigen. An Rh – person carries no antigens, but with exposure to Rh + blood, their immune system will become sensitized and begin to produce antibodies against the foreign blood type. Hemolysis – the rupturing of RBC’s with the second exposure to mismatched blood. In mothers who are Rh-, with fetuses that are Rh+, RhoGAM can be given to halt the reaction in the second pregnancy. Without RhoGAM the second fetus would most likely die of hemolytic disease of the newborn.

Blood type by ethnic group. Blood types by percentage population.