Anatomy

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Blood Objectives • List the components of the cardiovascular • Describe the important components and major functions of blood. • List the characteristics and functions of red blood cells. • Describe the structure of hemoglobin and indicate its functions. • Discuss red blood cell production and maturation. • Explain blood typing and the basis for ABO and Rh incompatibilities. • Categorize the various white blood cells on the basis of structure and function. • Describe the structure, function, and production of platelets. • Describe the reaction sequences responsible for blood clotting.

The cardiovascular system • A mechanism for rapid transport of nutrients, waste products, gases, and cells

Blood • Fluid connective tissue • Functions include

• Transporting dissolved gases, nutrients, hormones, and metabolic wastes • Regulating pH and ion composition of interstitial fluids • Restricting fluid loss at injury sites • Defending the body against toxins and pathogens • Regulating body temperature by absorbing and redistributing heat

• Physical Characteristics of Blood • Thicker & heavier than H2O • Temp. = 100.4°F (38°C) • Volume = 5-6 liters for males, 4-5 liters for females • Blood = 8% of total body weight

The composition of blood • Plasma (45%) and formed elements (55%) comprise whole blood

• Red blood cells (RBC) • White blood cells (WBC) • Platelets

• Can fractionate whole blood for analytical or clinical purposes

Hemopoiesis • Process of blood cell formation • Hemocytoblasts are circulating stem cells that divide to form all types of blood cells

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Plasma • 92 percent of plasma is water • Higher concentration of dissolved oxygen and proteins than interstitial fluid

Plasma proteins • More than 90 percent are synthesized in the liver • Albumins

• 60 percent of plasma proteins • Responsible for viscosity and osmotic pressure of blood

Additional Plasma Proteins • Globulins

• ~35 percent of plasma proteins • Include immunoglobins which attack foreign proteins and pathogens • Include transport globulins which bind ions, hormones, and other compounds

• Fibrinogen • Converted to fibrin during clotting • Removal of fibrinogen leaves serum

Abundance of RBCs • Erythrocytes account for 99.9 percent of the formed elements • Hematocrit measures the percentage of whole blood occupied by formed elements

• Commonly referred to as the volume of packed red cells

Structure of RBCs • Biconcave disc, providing a large surface to volume ration • Shape allows RBCs to stack, bend, and flex • RBCs lack organelles • Typically degenerate in about 120 days

Hemoglobin • Molecules of hemoglobin account for 95 percent of the proteins in RBCs • Hemoglobin is a globular protein, formed from two pairs of polypeptide subunits

• Each subunit contains a molecule of heme which reversibly binds an O2 molecule • Damaged or dead RBCs are recycled by phagocytes

RBC life span and circulation • Replaced at a rate of ≈ 3,000,000 new blood cells entering the circulation per second • Components of hemoglobin individually recycled

• Heme stripped of iron and converted to biliverdin, then bilirubin • Iron is recycled

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RBC production • Erythropoeisis = the formation of new red blood cells • Occurs in red bone marrow • Process speeds up with in the presence of EPO (erythropoietin)

• RBCs pass through reticulocyte and erythroblast stages

Blood types • Determined by the presence or absence of surface antigens (agglutinogens)

• Antigens A, B, and Rh (D) • Antibodies are in plasma (agglutinins) that do not react with antigens

• Cross-reactions only occur when antigens meet antibodies in incompatible transfusions • Incompatible blood transfusions cause donated RBC's to be attacked causing

agglutination (clump) • These cells lodge, swell & rupture: hemolysis • ***Hint: Donors RBC must be compatible with recipient’s plasma antibodies***

Blood Type Compatible Donor Types Incompatible Types A A, O B, AB B B, O A, AB AB A, B, AB, O --- O O A, B, AB

Rh System

First worked out on the rhesus monkey - Also based on antigens on RBC surface

Those with Rh antigens are Rh+ - Those without Rh antigens are Rh-

Normally plasma does not contain anti-Rh antibodies

Antibodies develop only upon greater exposure to Rh antigens

Donation reactions would occur only upon multiple incompatible transfusions

The most common problem is during pregnancy

Rh+ fetus & Rh- mother can cause problems in later pregnancies

Mom will be exposed to Rh+ blood during delivery and will then make anti-Rh antibodies

A second pregnancy will cause mom's anti-Rh antibodies to cross placenta

If fetus is Rh- there is no problem - If fetus is Rh+ hemolysis will occur in fetal blood

This is erythroblastosis fetalis (hemolytic disease of the newborn [HDN])

Kids born with this receive gradual transfusions before or after birth (with Rh-)

Injections to mom after first pregnancy can prevent problems w/ second

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Leukocytes • Have nuclei and other organelles • Defend the body against pathogens • Remove toxins, wastes, and abnormal or damaged cells • Are capable of amoeboid movement (margination) and positive chemotaxis • Some are capable of phagocytosis

Types of WBC • Granular leukocytes

• Neutrophils – 50 to 70 percent total WBC population • Eosinophils – phagocytes attracted to foreign cells that have reacted with antibodies • Basophils – migrate to damaged tissue and release histamine and heparin

Types of WBC • Agranular leukocytes

• Monocytes – become macrophage • Lymphocytes – includes T cells, B cells, and NK cells

Differential count • Indicates a number of disorders by determining which WBC is responding to disease

WBC Production • Granulocytes and monocytes are produced by bone marrow stem cells

• Divide to create progenitor cells • Stem cells may originate in bone marrow and migrate to peripheral tissues

• Lymphocytes originate in bone but develop in lymphoid tissue (thymus, spleen . .)

Platelets • Flattened discs • Circulate for 9-12 days before being removed by phagocytes

Platelet functions • Transporting chemicals important to clotting • Forming temporary patch in walls of damaged blood vessels • Contracting after a clot has formed

Platelet production (thrombocytopoiesis) • Megakaryocytes release platelets into circulating blood

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Hemostasis • Prevents the loss of blood through vessel walls • Three phases:

• Vascular phase • Platelet phase • Coagulation phase

Hemostasis • Vascular phase

• Local blood vessel constriction (vascular spasm) • Platelet phase

• Platelets are activated, aggregate at the site, adhere to the damaged surfaces • Coagulation phase

• Factors released by platelets and endothelial cells interact with clotting factors to form a clot • Basically: Fibrinogen in the presence of thrombin converts to Fibrin • Fibrin is the basic framework of a blood clot