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Blood 11.1 The Composition and Functions of Blood

Introduction Composition of blood; layers after centrifuging: Plasma Makes up 55% of whole blood by volume Formed elements Upper – buffy coat – white blood cells and platelets Lower – red blood cells

Composition of Blood

Composition of Blood, cont.

Introduction, cont. Hematocrit – percent of blood volume consisting of red blood cells Normally 45% Males usually have a higher hematocrit than females

Functions of Blood 1. Transportation 2. Defense 3. Regulation

Blood 11.2 Components of Blood

Plasma Liquid portion of blood 92% is water, 8% is various salts and organic molecules Plasma proteins – help maintain homeostasis in various ways

Plasma, cont. 4 Plasma proteins: Albumins Contribute to osmotic pressure Globulins Alpha and beta – produced by the liver; transport metals and vitamins Bind to lipids, forming lipoproteins Gamma – type of antibodies Fibrinogen – function in blood clotting Prothrombin – function in blood clotting

Plasma

Formed Elements Produced continuously in the red bone marrow of the: Skull Ribs Vertebrae Iliac crests Ends of long bones

Formed Elements

Formed Elements, cont. Hematopoiesis – Multipotent stem cells – red bone marrow cells that become other blood cells Replicate by mitosis Each daughter cell then differentiates into myeloid stem cells or lymphoid stem cells

Hematopoiesis

Formed Elements, cont. Hematopoiesis, cont. Myeloid stem cells further differentiate into: Red blood cells Granular leukocytes Monocytes Megakaryocytes Lymphoid stem cells differentiate into lymphocytes

Red Blood Cells (Erythrocytes) Small, biconcave disks Anucleate Very numerous: 4 to 6 million per mm3 of whole blood Function to transport oxygen

Red Blood Cells (Erythrocytes), cont. RBC’s contain proteins called hemoglobin – 200 million per RBC Respiratory pigment Oxyhemoglobin is formed when oxygen binds with hemoglobin – bright red Hemoglobin that is not combined with oxygen is called deoxyhemoglobin – dark maroon

Red Blood Cells (Erythrocytes), cont. Hemoglobin Contains four globin subunits that each contain a heme group In the lungs, the relatively higher oxygen concentration, cooler temperature and higher pH causes hemoglobin to readily bind oxygen In tissues, the relatively lower oxygen concentration, warmer temperature and lower pH causes it to give up oxygen

Red Blood Cell Production Myeloid stem cells give rise to erythroblasts, which divide many times As they mature, erythroblasts gain many molecules of hemoglobin and lose their nucleus and most of their organelles Reticulocytes are released into circulation, where they mature Mature RBCs live about 120 days About 2 million RBCs are produced per second to keep RBC count in balance Erythropoietin:

Regulation of Red Blood Cell Production

Red Blood Cell Destruction Destroyed in the liver and spleen by macrophages Hemoglobin is separated into its components Globin portion is broken down into amino acids that are recycled by the body Iron is recovered and returned to the bone marrow for reuse Heme portion is degraded into bile pigments (bilirubin and biliverdin), which are excreted by the liver

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Hemoglobin Breakdown

Abnormal RBC counts Anemia: Types of anemia: Hemolytic – inc. rate of RBC destruction Sickle-cell – genetic; abnormal hemoglobin Iron deficiency – low iron intake Pernicious – lack of vitamin B12 Aplastic – bone marrow damage Hemorrhagic – blood loss

White Blood Cells (Leukocytes) Usually larger than RBCs Nucleated Translucent unless stained Not as numerous as RBC’s; about 5,000-11,000 per mm3

White Blood Cells (Leukocytes), cont. Functions include: Fighting infection Destroying dead or dying body cells Recognizing and killing cancerous cells Derived from stem cells in the red bone marrow Able to leave the blood stream

Mobility of White Blood Cells

White Blood Cells (Leukocytes), cont. Types of white blood cells Granular leukocytes Neutrophils Most abundant First to respond to an infection Phagocytic Eosinophils Increase in number during parasitic worm infections Lessen an allergic reaction during an allergic attack

White Blood Cells (Leukocytes), cont. Basophils Release histamines – dilates blood vessels and causes contraction of smooth muscle Release heparin – prevents clotting and promotes blood flow

White Blood Cells (Leukocytes), cont. Agranular leukocytes Lymphocytes Specific immunity against particular pathogens and their toxins Recognize and destroy cancer cells B lymphocytes produce antibodies that will bind to antigens T lymphocytes attack and destroy any cell with a foreign antigen

White Blood Cells (Leukocytes), cont. Monocytes Largest of the WBCs Differentiate into macrophages Stimulate other WBCs to defend the body

Hematopoiesis

White Blood Cells (Leukocytes), cont. Abnormal white cell counts Leukopenia – Leukocytosis – Differential white blood cell count – Mononucleosis – viral infection; large number of abnormal lymphocytes Leukemia –

11.3 Platelets and Hemostasis Blood 11.3 Platelets and Hemostasis

Platelets (Thrombocytes) Not cellular - they are fragments of megakaryocytes 150,000-300,000 per mm3 of blood Lifespan about 10 days

Hemostasis Cessation of bleeding; self-limiting and confined to area of damage Three events: Vascular spasm – constriction of a broken blood vessel; platelets also release serotonin Platelet plug formation In a broken blood vessel, collagen fibers are exposed Platelets adhere to collagen and aggregation of platelets results in a platelet plug

Hemostasis, cont. 3. Coagulation – blood clotting Requires many protein clotting factors Two mechanisms for activation of clotting Intrinsic mechanism – clotting factors are intrinsic to the blood Slower than extrinsic mechanism Initiated when exposed to broken collagen in broken blood vessel wall

Hemostasis, cont. Extrinsic mechanism – clotting factors are extrinsic to the blood (from damaged tissue) Activated when damaged tissues release tissue thromboplastin Both intrinsic and extrinsic mechanisms are activated simultaneously; their common endpoint is the production of prothrombin activator

Hemostasis, cont. Four steps of coagulation: Prothrombin activator is formed Prothrombin activator converts prothrombin to thrombin Thrombin converts fibrinogen to fibrin Fibrin threads wind around platelet plug and trap RBCs

Process of Hemostasis

Hemostasis, cont. Clot retraction Clot gets smaller as platelets contract Serum is squeezed from the clot Serum is plasma minus fibrinogen and prothrombin Enzyme, plasmin, then breaks down the fibrin network after vessel repair begins

Hemostasis, cont. Conditions that prevent unwanted clot formation: Undamaged tissue Smooth endothelial lining of blood vessels Anticoagulants in the blood, e.g. heparin

Disorders of Hemostasis Thrombocytopenia – Hemophilia – Thrombus – Embolus – Thromboembolism – dislodged clot blocks a blood vessel Pulmonary thromboembolism Cerebrovascular accident or stroke

11.4 Blood Typing and Transfusions

Blood Typing and Transfusions Blood Transfusion Transfer of blood from one individual into another Blood must be typed so that agglutination does not occur Agglutination – clumping of red blood cells

ABO Blood Groups Blood groups are based on the presence or absence of inherited antigens on the surface of RBC’s Type A blood has type A antigen and anti-B antibodies Type B blood has type B antigen and anti-A antibodies Type AB blood has both A and B antigens and neither antibody Type O blood has neither A nor B antigens and both antibodies

Types of Blood

ABO Blood Groups, cont. Agglutination occurs if antibodies in the plasma combine with the antigens on the surface of the RBC Universal donor = Universal recipient = Autotransfusion technology and blood substitutes are alternatives to matching blood types

Cross-matching Before a Blood Transfusion

Transfusions

Rh Blood Groups If the Rh factor is present on the surface of RBC’s, the individual is Rh+; if not, they are Rh- Rh- individuals do not make antibodies against the Rh factor until they are exposed to it either through a transfusion or by carrying an Rh+ baby

Rh Blood Groups, cont. Hemolytic disease of the newborn (HDN) First pregnancy in an Rh- mother with an Rh+ fetus is safe; but in subsequent pregnancies with an Rh+ baby, HDN may occur Severe anemia may occur, and bilirubin can lead to brain damage or death Prevented by giving Rh- women an Rh immunoglobulin injection (RhoGAM), which has anti-Rh antibodies that attack fetal RBC’s that entered mother’s blood (before production of anti-Rh antibodies)

Hemolytic Disease of the Newborn

Blood 11.5 Effects of Aging

Effects of Aging Anemias increase Iron deficiency anemia Pernicious anemia Leukemia increases Clotting disorders, such as thromboembolism increase Associated with arteriosclerosis May be controlled by diet and exercise