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

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

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

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

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.

Blood Pressure and pulse Systolic pressure occurs during ventricular systole (contraction) When you can first hear the sound of blood flowing through the brachial artery Diastolic pressure occurs during ventricular diastole (relaxation) Point when you no longer hear the flow of blood

First heart sound due to closing of A-V valves Second heart sound due to closing of semilunar valves. Heart Murmurs – abnormal sounds caused by the flow of blood. Mitral stenosis Mitral valve prolapse

Blood pressure by pulse points Popliteal or dosalis pedis – (normal) Femoral Radial – 80 Carotid – 60 (exsanguination)

Anatomy of blood vessels Arteries carry blood away from the heart Hole is called the lumen Three layers or tunics: –Tunica interna (intima) –Tunica media –Tunica externa (adventitia)

Tunica interna Simple squamous epithelium called endothelium Secretes biochemicals that inhibit platelet aggregation Also substances that dilate or constrict vessels

Tunica media Bulk of vessel wall Smooth muscle fibers Innervated by the sympathetic N.S. – vasoconstriction; decreased impulses = vasodilation Thick layer of elastic connective tissue

Tunica externa Thin layer Connective tissue Attaches artery to surrounding tissue Contains tiny vessels – vasa vasorum that form capillaries and provide blood to external cells of the vessel

Arteries Large arteries are elastic (conducting) arteries – pressure reservoirs Medium arteries are muscular (distributing) arteries – more smooth muscle

Capillaries Only a single layer of endothelium and a basement membrane Connect arterioles and venules Microcirculation Functional part of system for exchange of gases, wastes and nutrients True capillaries begin at a precapillary sphincter

Types of capillaries Continuous - intercellular clefts, but otherwise uninterrupted Fenestrated capillaries – have “windows” or pores – act in filtration Sinusoids or discontinuous capillaries have spaces between cells, and basement membrane is incomplete or absent Tight junctions – form a barrier

Veins Have same three tunics as arteries, but have a thinner tunica media Contain valves Act as blood reservoirs