Leukocytes Protect against infection –phagocytize bacteria –produce proteins that destroy foreign particles Diapedesis: leukocytes can squeeze between cells and leave the circulation Figure 14.14

Figure 14.15

Leukocytes Positive chemotaxis: damaged cells release chemicals that attract leukocytes Inflammation delays spread of microorganisms

Blood Platelets Thrombocytes Arise from megakaryocytes in the red bone marrow Platelets are small and lack a nucleus Help repair broken blood vessels Release serotonin

Blood Plasma 92% water Plasma proteins Gases and nutrients Nonprotein nitrogen substances –amino acids, urea, uric acid, creatine, creatinine Plasma electrolytes –sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, sulfate

Plasma Proteins Albumins –60% of plasma proteins –maintain osmotic pressure, bind and transport molecules

Plasma Proteins Globulins –36% of plasma proteins –alpha, beta, gamma globulins Fibrinogen –4% of plasma proteins –primary role in blood clotting

Figure 14.16

Blood Gases and Nutrients Blood gases –oxygen and carbon dioxide Nutrients –amino acids, simple sugars, nucleotides, lipids –Lipids include triglycerides, phospholipids, cholesterol transported as lipoproteins chylomicrons, VLDL, LDL, HDL

Hemostasis Stoppage of bleeding to prevent blood loss Blood vessel spasm –vasospasm due to smooth muscle contraction –direct stimulation of vessel wall and pain reflexes

Hemostasis Platelet plug formation –platelets become spiny and sticky and plug the vascular break Figure 14.17

Blood Coagulation Complex cascade of events Utilizes clotting factors Vitamin K is necessary for clotting factors Major event is conversion of soluble plasma protein fibrinogen to insoluble treads of fibrin

Extrinsic Clotting Mechanism Triggered when blood contacts damaged blood vessel wall or tissue outside blood vessels Damaged tissue releases thromboplastin Thromboplastin activates clotting cascade These reactions with calcium release prothrombin Prothrombin is converted into thrombin Thrombin converts fibrinogen to fibrin

Extrinsic Clotting Mechanism Fibrin threads stick to exposed damaged blood vessels. Meshwork traps blood cells and platelets. This produced a blood clot. The amount of prothrombin activator is proportional to the degree of tissue damage. Blood clotting is self-initiating, a positive feedback system.

Clot Limitation Blood flow keeps thrombin concentration low Antithrombin limits thrombin formation Thrombus: a clot abnormally forming in a vessel Embolus: a dislodged clot carried by the bloodstream Embolism: embolus blocking blood flow

Intrinsic Clotting Mechanism All components found in the blood Activation of Hageman Factor initiates intrinsic clotting Cascade of activation in the presence of calcium produces prothrombin activator Prothrombin and fibrin are formed as in the extrinsic pathway

Figure 14.19

Fate of Blood Clots Blood clot retraction occurs pulling torn vessel ends together. Serum is squeezed out. Platelet-derived growth factor repairs wall. Plasminogen is absorbed by fibrin. Plasminogen activator converts plasminogen to plasmin. Plasmin digests the clot.

Prevention of Coagulation Endothelial cells produce prostacyclin which inhibits platelet adherence. Antithrombin inactivates thrombin. Basophils and mast cells release heparin which interferes with the formation of prothrombin activator.

Antigens and Antibodies Blood cell compatibility is based on clumping or agglutination Transfusion reaction: a reaction between red blood cell antigens or agglutinogens and protein antibodies or agglutinins in the plasma Antigens include those of the ABO group and the Rh group

Figure 14.22

ABO Blood Group Based on red blood cell membrane antigen A and antigen B

ABO Blood Group Four possible combinations –Type A contains antigen A –Type B contains antigen B –Type AB contains antigens A and B –Type O contains no antigens Figure 14.21

ABO Blood Group Anti-A and anti-B antibodies are produced when an antigen is absent from the cell membrane –Type A plasma contains anti-B antibodies –Type B plasma contains anti-A antibodies –Type AB plasma contains anti-A and anti-B antibodies, universal recipient –Type O plasma contains no antibodies, universal donor

Rh Blood Group Rh positive indicates presence of antigen D, one of the Rh antigens Rh negative indicates absence of Antigen D Figure 14.23

Rh Blood Group Rh antigens, like A and B antigens are inherited and present from birth Anti-D antibodies and not produced until after an individual is sensitized to D antigen