Blood

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Lecture Outline

The Composition and Functions of Blood

o Functions of Blood• Transport

Carries oxygen to tissues Carries carbon dioxide and other wastes away

from tissues Hormones

• Defense Defends body against pathogens Removes dead and dying cells

• Regulation Body temperature Water-salt balance Body pH

Components of Blood

o Plasma• Liquid portion of blood• About 92% is water• About 8% is composed various salts

and organic molecules• Plasma proteins

Albumins Globulins

Alpha and beta – produced by the liver Gamma - antibodies

Fibrinogen – functions in blood clotting Help maintain homeostasis

Formed Elements

o Produced continuously in the red bone marrow of the:

• Skull• Ribs• Vertebrae• Iliac crests• Ends of long bones

Formed Elements

o Hematopoiesis• Multipotent stem cells – red bone

marrow cells• Multipotent cells replicate• Each daughter cell then differentiates

Myeloid stem cells further differentiates Red blood cells Granular leukocytes Monocytes Megakaryocytes

Lymphatic stem cells differentiate to produce the lymphocytes

Formed Elements

o Red Blood Cells (erythrocytes)• Small, biconcave disks• Anucleate• 4 to 6 million per mm3

• Transport oxygen• Contain hemoglobin

Respiratory pigment Oxyhemoglobin is formed when oxygen

binds with hemoglobin Hemoglobin that is not combined with

oxygen is called deoxyhemoglobin

Formed Elements

• Production of red blood cells Myeloid stem cells give rise to

erythroblasts Erythroblasts divide many times As they mature, erythroblasts gain many

molecules of hemoglobin and lose their nucleus and most of their organelles

Mature RBCs live about 120 days About 2 million RBCs are produced per

second to keep RBC count in balance Erythropoietin stimulates production and

maturation of RBCs

Formed Elements

• Destruction of red blood cells Destroyed in the liver and spleen Hemoglobin is released

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 and is excreted as bile pigments by the liver Bilirubin Biliverdin

Formed Elements

• Anemia Illness characterized by tiredness Cells are not getting enough oxygen due

to decreased hemoglobin or decreased number of red blood cells

Hemolysis can also cause anemia

Formed Elements

o White Blood Cells (leukocytes)• Usually larger than RBCs• Nucleated• Do not contain hemoglobin• About 5,000-11,000 per mm3

• 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

Formed Elements

• Types of White Blood Cells Granular leukocytes

Neutrophils Most abundant of the WBCs First type of WBC to respond to an infection Engulf pathogens during phagocytosis

Eosinophils Increase in number during parasitic worm

infections Lessen an allergic reaction during an allergic

attack Basophils

Release histamines – dilates blood vessels and causes contraction of smooth muscle

Release heparin – prevents clotting and promotes blood flow

Formed Elements

Agranular leukocytes Lymphocytes

Specific immunity Recognize and destroy cancer cells B lymphocytes produce antibodies T lymphocytes attack and destroy any cell

with a foreign antigen Monocytes

Largest of the WBCs Differentiate into macrophages that

phagocytize pathogens, old cells, and cellular debris

Stimulate other WBCs to defend the body

Platelets and Hemostasis

o Platelets• Fragments of megakaryocytes• 150,000-300,000 per mm3 of blood• Lifespan about 10 days

o Hemostasis• Cessation of bleeding• 3 events:

Vascular spasm – constriction of a broken blood vessel

Platelet plug formation In a broken blood vessel, collagen fibers are exposed Platelets adhere to collagen and aggregation of

platelets result in a platelet plug

Platelets and Hemostasis

Coagulation – blood clotting Requires many protein clotting factors Two mechanisms for activation of clotting

Intrinsic mechanism – clotting factors intrinsic to the blood – exposed collagen

Extrinsic mechanism – clotting factors extrinsic to the blood - thromboplastin

Clotting process is self-limiting and confined to the area of injury

Platelets and Hemostasis

Four steps: Prothrombin activator is

formed Prothrombin activator

converts prothrombin to thrombin

Thrombin converts fibrinogen to fibrin

Fibrin threads wind around platelet plug and trap RBCs

Platelets and Hemostasis

• Disorders of hemostasis Thrombocytopenia – low platelet count Hemophelias – inherited clotting disorders

caused by deficiencies of clotting factors Thrombus – stationary blood clot Embolus – dislodged blood clot Thromboembolism – dislodged clot blocks

a blood vessel Pulmonary thromboembolism Cerebrovascular accident or stroke

Capillary Exchange

• Lymph has the same composition as tissue fluid

• Edema Localized swelling Accumulation of tissue fluid Caused by:

Increase in capillary permeability Decrease in the uptake of water at the venous

end of blood capillaries Increase in venous pressure Insufficient uptake of tissue fluid by the

lymphatic capillaries Blocked lymphatic vessels

Blood Typing and Transfusions

o Blood transfusion• Transfer of blood from one individual

into the blood of another• Blood must be typed so that

agglutination does not occur

Blood Typing and Transfusions

o ABO Blood Groups• Based on the presence or absence of

inherited antigens• 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 antigens and

neither antibodies• Type O blood has no AB antigens and

both antibodies

Blood Typing and Transfusions

• Agglutination occurs if antibodies in the plasma combine with the antigens on the surface of the RBC

• Type O blood is the universal donor

• Type AB blood is the universal recipient

• Autotransfusion technology and blood substitutes are alternatives to matching blood types

Blood Typing and Transfusions

o Rh Blood Groups• Rh- individuals do not have antibodies to the Rh factor until

they are exposed to it• Hemolytic disease of the newborn

May occur in subsequent pregnancies with an Rh+ baby and an Rh- mother

Bilirubin in the blood of the newborn can lead to brain damage or death

Prevented by giving Rh- women an Rh immunoglobulin injection

Effects of Aging

o Anemia• Iron deficiency anemia• Pernicious anemia

o Leukemiao Clotting disorders, such as

thromboembolism• Associated with arteriosclerosis• May be controlled by diet and

exercise