1. Chapter 17 Blood

2. Composition of Blood Introduction –Blood – 8% of total body weight 55% plasma 45% formed elements (Table 17-1) Complex transport medium –Picks up food and oxygen, delivers to cells –Picks up waste, delivers to excretory organs –Hormones, enzymes, buffers Keystone of body’s heat-regulating mechanism –Blood volume 4-6 liters in adults Blood volume varies according to age, body type, sex, and method of measurement

6. Formed Elements of Blood Red blood cells (erythrocytes) –No nucleus –Biconcave disks –Do not contain ribosomes, mitochondria, and other organelles typical of most body cells –Primary component is hemoglobin –Most numerous of the formed elements 5,500,000 per mm 3 in men 4,800,000 per mm 3 in women

7. Formed Elements of Blood Function of RBCs –Transport of oxygen and carbon dioxide Depends on hemoglobin and carbonic anhydrase –Joins carbon dioxide and water to form carbonic acid –Carbonic acid dissociates to form bicarbonate ions –Ions are transported in blood plasma until excreted –Bicarbonate ions also maintain blood pH levels –Total surface area of RBCs is greater than a football field

8. Formed Elements of Blood Red blood cells (erythrocytes) (cont.) –Hemoglobin Approximately 200 to 300 million molecules of hemoglobin per RBC Made up of four globin chains, each attached to a heme molecule Hemoglobin is able to unite with four oxygen molecules to form oxyhemoglobin to allow RBCs to transport oxygen where it is needed A male has a greater amount of hemoglobin than a female –12-16 g of hemoglobin per 100 ml of blood Anemia—a decrease in number or volume of functional RBCs in a given unit of whole blood

11. Formed Elements of Blood Red blood cells (erythrocytes) (cont.) –Erythropoiesis—entire process of RBC formation (Figure 17-6) Begins in the red bone marrow with hematopoietic stem cells –Several stages of development –Process takes ~4 days 100 million RBCs are created and destroyed per minute in an adult RBC production increases if oxygen deficiency occurs

13. Formed Elements of Blood Red blood cells (erythrocytes) (cont.) –Destruction of RBCs (Figure 17-8) Life span of a circulating RBC averages 105 to 120 days Macrophage cells phagocytose the aged, abnormal, or fragmented RBCs…often in the lining of blood vessels of the liver and spleen Hemoglobin is broken down and amino acids, iron, and bilirubin are released –Iron is returned to bone –Amino acids are used in protein synthesis –Bilirubin is transported to the liver and excreted as part of bile »Gives feces its characteristic color

14. Formed Elements of Blood White blood cells (leukocytes, WBCs) –Granulocytes Neutrophils –Approximately 65% of total WBCs –Highly mobile and very active phagocytic cells –Capable of diapedesis –Cytoplasmic granules contain lysosomes Eosinophils –2% to 5% of circulating WBCs –Numerous in lining of respiratory and digestive tracts –Weak phagocytes –Capable of ingesting inflammatory chemicals and proteins associated with antigen- antibody reaction complexes –Provide protection against infections caused by parasitic worms and allergic reactions Basophils –Only 0.5% to 1% of circulating WBCs –Motile and capable of diapedesis –Cytoplasmic granules contain histamine and heparin

15. Formed Elements of Blood White blood cells (cont.) –Agranulocytes Lymphocytes –Smallest of the WBCs –Second most numerous type of WBC –Approximately 25% of circulating WBCs –T lymphocytes and B lymphocytes have an important role in immunity »T lymphocytes directly attack an infected or cancerous cell »B lymphocytes produce antibodies against specific antigens Monocytes –Largest type of leukocyte –Mobile and highly phagocytic cells

16. Formed Elements of Blood White blood cells (cont.) –WBC numbers 5,000-9,000 per mm 3 Change with certain abnormal conditions –Formation of WBCs Granular and agranular leukocytes mature from the undifferentiated hemopoietic stem cell Neutrophils, eosinophils, basophils, and a few lymphocytes and monocytes originate in red bone marrow Most lymphocytes and monocytes develop from hemopoietic stem cells in lymphatic tissue

17. Formed Elements of Blood Platelets –Structure Small, pale bodies that appear as irregular spindles or oval disks Three important properties –Agglutination –Adhesiveness –Aggregation 250,000 per mm 3 of blood 150,000 to 400,000 per mm 3 is normal –Functions of platelets Hemostasis Blood clotting/coagulation

18. Formed Elements of Blood Platelets (cont.) –Platelet plug formation 1 to 5 seconds after injury to vessel wall, platelets adhere to damaged endothelial lining and to each other, forming a platelet plug Temporary platelet plug is an important step in hemostasis Normal platelets (positive charge) adhere to damaged capillary wall and underlying collagen fibers, which both have a negative charge “Sticky platelets” form physical plug and secrete several chemicals involved in the coagulation process –Formed in red bone marrow, lungs, and spleen by fragmentation of megakaryocytes –Life span of 7 to 10 days