Blood Chapter 14

Blood Connective tissue with a fluid matrix Three main functions: –Transportation –Regulation –Protection

Physical Characteristics of Blood Heavier, thicker, and 3-4 X more viscous than water 38 o C (100.4 o F) pH : 7.35 – % of body weight 4-6 liters in an adult Varies with electrolyte concentration and amount of adipose tissue

8% of body weight 70 kg person Total blood weight = 0.08 X 70kg = 5.6 kg One kilogram of blood ≈ 1 liter Total blood volume = 5.6 liters

Components of Blood Plasma – 55 % Formed elements – cells and cell fragments – 45% Hematocrit (HCT) or Packed Cell Volume (PCV) See: –Plasma –Buffy coat (< 1%) –Red cells - erythrocytes

Formation of blood cells Before birth blood is formed by the yolk sac, liver, spleen, thymus gland, lymph nodes and red bone marrow. After birth only by red bone marrow Stem cells are hemocytoblasts Process is hematopoiesis Colony stimulating factors

Erthrocytes Biconcave discs without nuclei 1/3 hemoglobin by volume Hemoglobin – 4 peptide chains and an iron containing pigment called heme The iron binds reversibly with oxygen oxyhemoglobin deoxyhemoglobin Cyanotic – skin and mucous membranes appear blue

Also transports 23 % of CO 2 bound to globin as carbaminohemoglobin CO – carbon monoxide binds more tightly to hemoglobin than oxygen Males = 5.4 million RBCs per cubic mm Females and children = 4.8 million/ cubic mm People at high altitudes = 8 million/cubic mm

RBCs live about 120 days Iron is removed from heme, combines with transferrin and is taken to bone marrow 80% of the iron is stored in the liver in an iron-protein complex called ferritin

The rest of the heme is a greenish pigment called biliverdin which is broken down to a yellow-orange substance called bilirubin Jaudice

Anemia is the inability of the blood to carry sufficient oxygen to the body. low #’s of RBCs lack of hemoglobin

Pernicious anemia is a lack of RBCs due to lack of vitamin B12 Folic acid also needed for DNA synthesis Iron deficiency anemia Sickle cell anemia Polycythemia is an excess of RBCs – blood gets too thick to flow

Leukocytes Granular leukocytes (granulocytes) neutrophils eosinophils basophils Agranular leukocytes (agranulocytes) Lymphocytes Monocytes

Eosinophils Granules stain red with acidic dyes Nuclei us. have 2 lobes Combat effect of histamine in allergic reactions Combat parasitic worms 1-3% of leukocytes

Basophils Have granules that stain blue with basic dyes Release heparin, and histamine Increase in allergic reactions that intensify the inflammatory response Less than 1% of leukocytes

Neutrophils Granules stain pale purple in a combination of acidic and basic dye Older cells have many lobed nuclei – gives the name polymorphonuclear leukocytes (PMNs) Younger neutrophils are called bands Phagocytes % of the leukocytes

Lymphocytes May be small or large Nuclei stain darkly, very little cytoplasm Only 2% of lymphocytes are in blood B lymphocytes make antibodies T lymphocytes attack invaders directly Long lived 25-33% of leukocytes

Monocytes Largest leukocyte Nuclei horseshoe-shaped Cytoplasm blue-gray and foamy When leave blood and enter tissues become transformed into macrophages % of leukocytes

Normal blood contains 5, ,000/mm 3 An increase in the number of wbcs is leukocytosis A deficiency in wbcs is leukopenia Differential white blood cell count is useful in diagnosis of disease Major histocompatibility (MHC) antigens used in tissue typing

Function of leukocytes Protect against infection phagocytosis, antibodies, direct attack Diapedesis Damaged tissue releases chemicals that attract leukocytes – positive chemotaxis

Platelets, or thrombocytes, are cell fragments Formed from megakaryocytes 130,000 – 360,000/mm 3 Involved in blood clotting Release serotonin which contracts smooth muscle in walls of blood vessels – reducing blood flow – and blood loss

Plasma 92 % water 8% solutes – ions, nutrients, enzymes, gases, wastes, hormones, but mostly proteins These proteins are mostly made by the liver

Serum Plasma without the clotting factors Still contains : ions, nutrients, enzymes, gases, wastes, hormones, and some proteins – including antibodies

Hemostasis Means stoppage of bleeding 1.Vascular spasm 2.Platelet plug formation 3.Blood coagulation - clotting

Vasospasm Smooth muscle in vessel wall contracts Decreased diameter of vessel decreases blood flow Lasts several minutes to several hours

Platelet plug formation 1.Platelets contact damaged vessel – platelet adhesion 2.Platelets become activated, dump granules – platelet release reaction 3.Platelets become sticky and accumulate – platelet aggregation

Blood coagulation Clotting in an unbroken vessel – thrombosis Clot is a thrombus If it breaks free and travels in the blood stream it is an embolus If it lodges elsewhere in the body, it is an embolism

Blood clotting can be divided into 3 stages: 1. formation of prothrombinase 2.Conversion of prothrombin to thrombin 3.Conversion of soluble fibrinogen to insoluble fibrin

Stage 1 formation of prothrombinase (prothrombin activator) can be started one of two ways: Extrinsic pathway (clotting mechanism): tissue factor leaks into the blood from outside the vessels Intrinsic pathway –more complex, slower, by roughened endothelium of exposure to foreign substances – Hageman factor

Stage 2 – Prothrombinase + calcium Convert prothrombin to thrombin Stage 3 – Thrombin + calcium convert fibrinogen to fibrin Threads of fibrin form a net and trap blood cells, forming a clot. Clot retraction Platelet-derived growth factor → repair

Hemophila Due to a deficiency of one of the clotting factors Hereditary trait

Role of vitamin K Normal clotting requires vitamin K, but it is not a clotting factor It is required for the synthesis of four of the clotting factors by the liver. Normally made by bacteria in large intestine Sometimes given before surgery

Fibrolytic system Plasminogen, an inactive enzyme, is incorporated into a clot Plasminogen can be activated to plasmin, (or fibrinolysin) which digests fibrin and inactivates other clotting factors

Thrombolytic agents Streptokinase Tissue plasminogen activator – t-PA

Anticoagulants Prostaglandins Heparin Warfarin or coumadin – antagonists to vitamin K Chelating agents tie up calcium Aspirin inhibits vasoconstriction and platelet aggregation

Blood Groups and Blood Types Erythrocytes have surface antigens, called isoantigens or agglutinogens Most common are the ABO and Rh groups A and B are isoantigens, O is absence of antigen Antibodies activate complement which causes hemolysis Typing outside the body uses agglutination, NOT clotting !

Persons with type A blood make antibodies against B Persons with type B blood make antibodies against A Persons with type O blood make antibodies against A and B Persons with type AB do not make antibodies.

Rh factor First discovered in the rhesus monkey Either have the antigen = positive Or don’t have the antigen = negative Do not automatically make antibodies – must first encounter the antigen Hemolytic disease of the newborn – or- erythroblastosis fetalis Give RhoGAM – anti Rh antibodies

Remember: Rh factor is only a problem if the mother is negative and the father is positive.