FORMED ELEMENTS OF BLOOD (cont.)  Functions of platelets  Important role in hemostasis and blood coagulation; secondary role in defending against bacterial attacks  Hemostasis: refers to stoppage of blood flow; however, if injury is extensive, the blood-clotting mechanism is activated to assist

FORMED ELEMENTS OF BLOOD (cont.)  Platelet plug formation  One to five 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, both of which have a negative charge  “Sticky platelets” form physical plug and secrete several chemicals involved in the coagulation process  Formation and life span of platelets (7 to 10 days): formed in red bone marrow, lungs, and spleen by fragmentation of megakaryocytes

© 2012 Pearson Education, Inc Platelets Platelet Counts 150,000 to 500,000 per microliter Thrombocytopenia Abnormally low platelet count Thrombocytosis Abnormally high platelet count

© 2012 Pearson Education, Inc White Blood Cells - nomenclature WBC Disorders Leukopenia Abnormally low WBC count Leukocytosis Abnormally high WBC count Leukemia A malignancy of the bone marrow, often with an extremely high WBC count, (and the WBC’s are cancerous- it is not just the # which is abnormal)

© 2012 Pearson Education, Inc Physical Characteristics of Blood Important Functions of Blood Transportation of dissolved substances Regulation of pH and ions Restriction of fluid losses at injury sites Defense against toxins and pathogens Stabilization of body temperature

© 2012 Pearson Education, Inc Physical Characteristics of Blood Three Types of Formed Elements 1. Red blood cells (RBCs) or erythrocytes Transport oxygen 2. White blood cells (WBCs) or leukocytes Part of the immune system 3. Platelets Cell fragments involved in clotting

© 2012 Pearson Education, Inc Physical Characteristics of Blood Three General Characteristics of Blood 1.38  C (100.4  F) is normal temperature (1 0 higher than body) 2. High viscosity 3. Slightly alkaline pH (7.35–7.45)

© 2012 Pearson Education, Inc Blood Typing Surface Antigens Are cell surface proteins that identify cells to immune system Normal cells are ignored and foreign cells attacked Blood Types Are genetically determined By presence or absence of RBC surface antigens A, B, Rh (or D)

BLOOD TYPES: BLOOD GROUPS  The ABO system  Every person’s blood belongs to one of four ABO blood groups  Named for antigens on RBC membranes  Type A: antigen A on RBCs  Type B: antigen B on RBCs  Type AB: both antigens A and B on RBCs; known as universal recipient  Type O: neither antigen A nor B on RBCs; known as universal donor

© 2012 Pearson Education, Inc. Figure 19-7a Blood Types and Cross-Reactions Type A Type B Type A blood has RBCs with surface antigen A only. Type B blood has RBCs with surface antigen B only. Surface antigen A Surface antigen B If you have Type A blood, your plasma contains anti-B antibodies, which will attack Type B surface antigens. If you have Type B blood, your plasma contains anti-A antibodies, which will attack Type A surface antigens.

© 2012 Pearson Education, Inc. Figure 19-7a Blood Types and Cross-Reactions Type AB Type O Type AB blood has RBCs with both A and B surface antigens. Type O blood has RBCs lacking both A and B surface antigens. If you have Type AB blood, your plasma has neither anti-A nor anti-B antibodies. If you have Type O blood, your plasma contains both anti-A and anti-B antibodies.

So,  A person with Type A blood will carry anti B antibodies A person with Type B blood will carry anti A antibodies A person with Type AB blood will carry NEITHER anti A NOR anti B antibodies !!! A person with Type O blood will carry BOTH anti A AND anti B antibodies

Agglutination - it means ‘clumping’ A donor A recipient B recipient A donor

BLOOD TYPES The Rh system  Rh: the RHESUS ANTIGEN  the Rh antigen is either present or absent on the RBCs  Rh-negative: RBCs have no Rh antigen present  Anti-Rh antibodies are not normally present in blood; even on Rh negative blood  BUT, anti-Rh antibodies can appear in Rh-negative blood if it has come in contact with Rh-positive RBCs, such as when an Rh- mother gives birth to an Rh + baby. Usually it only becomes a problem in a future pregnancy with another Rh positive baby.

 U.S. Blood-type Distribution  O+ 38 percent of population  A+ 34 percent of population  B+ 9 percent of population  O- 7 percent of population * Universal donor  A- 6 percent of population  AB+ 3 percent of population * Universal recipient  B- 2 percent of population  AB- 1 percent of population  * refers to Packed RBC’s, not whole blood

So, let’s practice some ‘type and cross matches:  BP, who has blood type B+, is involved in an auto accident and has been bleeding. BP’s Hemoglobin (Hgb) is down to 7.4 and is dropping. The call goes out for blood donors. BP’s classmates respond, but of the following, who will make suitable donor/s: A. AN : Type A – D. OP Type O+ G. ABN AB- B. ON: Type O- E. BP Type BP H. ABP AB+ C. BN: Type B- F. AP A+

Answer  B+ recipient: Possible donors: B+ O+ B- O- B- recipient: only poss. Donors B- O-

 Months later OP, who has blood type O+and had donated blood for BP, is now severely anemic due to a hemolytic reaction to a new medication, and her Hemoglobin (Hgb) is 6.5. BP, now healthy again, and so grateful, insists on donating his blood for OP. Can his blood be used? Of the classmates below, who would be suitable donors? A. AN : Type A – D. OP Type O+ G. ABN AB- B. ON: Type O- E. BP Type BP H. ABP AB+ C. BN: Type B- F. BN Type B- I. AP A+

Answer  O+ recipient:  only possible donor s O+ O- (because the O recipient will have ANTIBODIES to A and B antigens, Which would agglutinate types A, B, and AB red blood cells )

BLOOD PLASMA  Plasma: liquid part of blood; clear, straw-colored fluid; composed of 90% water and 10% solutes)  Solutes: most of the plasma solutes are PROTEINS, consisting of three main compounds  Albumins: help maintain osmotic balance of the blood  Globulins: essential component of the immunity mechanism  Fibrinogen: key role in blood clotting (and other ‘clotting factors’)  Plasma proteins have an essential role in maintaining normal blood circulation

BLOOD CLOTTING: COAGULATION  Mechanism of blood clotting:  goal of coagulation is to stop bleeding and prevent loss of vital body fluid in a swift and sure method  Classic theory of coagulation advanced 1905  Identified four components critical to coagulation  Prothrombin  Thrombin  Fibrinogen  Fibrin

BLOOD CLOTTING: COAGULATION  Current explanation of coagulation involves three stages  Stage 1: production of thromboplastin activator by either of the following:  Chemicals released from damaged tissues (extrinsic pathway)  Chemicals present in the blood (intrinsic pathway)  Stage 2: conversion of prothrombin to thrombin  Stage 3: conversion of fibrinogen to fibrin and production of fibrin clot

COMMON PATHWAY

THE BOTTOM LINE TO REMEMBER: (the common coaglation pathway)  Prothrombin (factor II), >>>>>> THROMBIN which activates fibrinogen ( factor I) Fibrin Network, clot

BLOOD CLOTTING: COAGULATION (cont.)  Conditions that oppose clotting  Clot formation in intact vessels is opposed  Several factors oppose clotting  Perfectly smooth surface of the normal endothelial lining of blood vessels does not allow platelets to adhere  Antithrombins: substances in the blood that oppose or inactivate thrombin; prevent thrombin from converting fibrinogen to fibrin (e.g., heparin)

BLOOD CLOTTING: COAGULATION (cont.)  Conditions that hasten clotting  Rough spot in the endothelium  Abnormally slow blood flow  Clot dissolution Fibrinolysis: physiological mechanism that dissolves clots  Fibrinolysin: enzyme in the blood that catalyzes the hydrolysis of fibrin, causing it to dissolve  Additional factors are presumed to aid clot dissolution (e.g., substances that activate profibrinolysin)

© 2012 Pearson Education, Inc. Fibrinolysis Slow process of dissolving clot Thrombin and tissue plasminogen activator (t-PA) Activate plasminogen Plasminogen produces plasmin Which digests fibrin strands

THE BIG PICTURE: BLOOD AND THE WHOLE BODY  Blood plasma transports substances, including heat, around the body, linking all body tissues together  Substances can be transported between almost any two points in the body  Blood tissue contains formed elements—blood cells and platelets  RBCs assist in the transport of oxygen and carbon dioxide  WBCs assist in the defense mechanisms of the whole body  Platelets prevent loss of the fluid that constitutes the internal environment  No organ or system of the body can maintain proper levels of nutrients, gases, or water without direct or indirect help from blood  Other systems assist the blood  Blood is useless unless it continues to transport, defend, and maintain balance