Essentials of Human Anatomy BLOOD Chapter 9 Dr

Essentials of Human Anatomy BLOOD Chapter 9 Dr Fadel Naim Ass. Prof. Faculty of Medicine IUG 1

Blood • Considered a connective tissue: contains – Cells – a liquid ground substance (called plasma) – dissolved protein fibers. • About four times more viscous (or thicker) than water. • Temperature of blood is about 1°C higher than measured body temperature.

Blood Volume • varies with • body size • changes in fluid concentration • changes in electrolyte concentration • amount of adipose tissue • about 8% of body weight • about 5 liters

Blood • Whole blood can be separated: – Liquid component – cellular components

Components of Blood • Erythrocytes (or red blood cells) – form the lower layer of the centrifuged blood – typically make up about 44% of a blood sample • Buffy coat – makes up the middle layer – thin, slightly gray-white layer composed of cells called leukocytes (or white blood cells) and cell fragments called platelets – forms less than 1% of a blood sample • Plasma – straw-colored liquid that rises to the top – generally makes up about 55% of blood

Components of Blood • Erythrocytes and the components of the buffy coat are called the formed elements. • Formed elements and the liquid plasma compose whole blood.

Functions of Blood – Transportation • Transports numerous elements and compounds throughout the body. – erythrocytes carry oxygen from the lungs to body cells and then transport carbon dioxide from the cells back to the lungs for expulsion from the body – blood plasma transports • nutrients that have been absorbed from the GI tract • hormones secreted by the endocrine organs to their target cells – plasma • carries waste products from the cells to organs such as the kidneys, where these waste products are removed

Functions of Blood – Regulation of Body Temperature • Regulates body temperature. – plasma absorbs and distributes heat throughout the body – for cooling the blood vessels in the dermis dilate and dissipate the excess heat through the integument – when the body needs to conserve heat, the dermal blood vessels constrict, and the warm blood is shunted to deeper blood vessels in the body

Functions of Blood – Regulation of p. H Levels • p. H is a measure of how alkaline or acidic a fluid is. – Neutral p. H is measured at exactly 7. – Acidic fluids (e. g. , orange juice) are between 0 and 7. – Alkaline fluids (e. g. , milk) are between 7 and 14. • Blood plasma contains compounds and ions that may be distributed to the fluid among tissues (interstitial fluid) to help maintain normal tissue p. H. • Blood plasma p. H is continuously regulated at a value of 7. 4 the p. H level required for normal cellular functioning.

Functions of Blood – Maintenance of Fluid Levels • Maintains normal fluid levels in the cardiovascular system. • Prevents fluid loss. • Constant exchange of fluid between the blood plasma and the interstitial fluid. – If too much fluid is absorbed in the blood, high blood pressure results. – If too much fluid escapes the bloodstream and enters the tissues, blood pressure drops to unhealthy low levels, and the tissues swell with excess fluid. • To maintain balance of fluid exchange between the blood and the interstitial fluid, blood contains compounds (such as salts and some proteins) to prevent excess fluid loss in the plasma.

Functions of Blood – Protection • Leukocytes (white blood cells) help guard against infection by mounting an immune response if a pathogen or an antigen is found. • Plasma transports antibodies, which are molecules that can immobilize antigens until a leukocyte can completely kill or remove the antigen. • Platelets and blood proteins protect the body against blood loss by forming blood clots on damaged vessels.

Components of Plasma • Complex mixture of water, proteins, and other solutes. • When the proteins are moved from plasma, the remaining fluid is termed serum. • Water makes up about 92% of plasma’s total volume. – water facilitates the transport of materials in the plasma Transports organic and inorganic molecules, formed elements, and heat • Water • Plasma proteins • Other solutes 92% 7% 1%

Plasma Proteins • The next most abundant materials in plasma are the plasma proteins. • Make up about 7% of the plasma. – 6 and 8 grams of protein in a volume of 100 milliliters of blood (referred to as g/dl) • The plasma proteins include: – – albumins globulins fibrinogen regulatory proteins

Difference between Plasma and Interstitial Fluid Plasma has more: • Dissolved O 2 diffuses out into tissue • Dissolved proteins (too big to cross caps. ) – Albumins – Globulins • globulins • and globulins – Fibrinogen Similar concentration: Salts & small molecules

Plasma Electrolytes • absorbed from the intestine or released as by-products of cellular metabolism • sodium • potassium • calcium • magnesium • chloride • bicarbonate • phosphate • sulfate • sodium and chloride are most abundant

Formed Elements in the Blood • Erythrocytes – make up more than 99% of formed elements – primary function is to transport respiratory gases in the blood • Leukocytes – make up less than. 01% of formed elements – contribute to defending the body against pathogens • Platelets – make up less than 1% of formed elements and – help with blood clotting

Hematocrit • Percentage of erythrocytes in the blood. • Values vary slightly and are dependent on age and sex. • Adult males range between 42% and 56%. • Females range from 38% to 46%. • Childrens’ hematocrit ranges also vary and differ from adult values. • Altitude can affect the hematocrit. – body compensates by making more erythrocytes – more erythrocytes in the blood can carry more oxygen to the tissues

Erythrocytes • Mature erythrocytes lack nuclei. • Transport oxygen and carbon dioxide to and from the tissues and the lungs. • Lack of nuclei enables them to carry respiratory gases more efficiently.

Hemoglobin in Erythrocytes • Every erythrocyte is filled with approximately 280 million molecules of a red-pigmented protein called hemoglobin. • Transports oxygen and carbon dioxide, and is responsible for the characteristic bright red color of arterial blood. • Hemoglobin that contains no oxygen has a deep red color that is perceived as blue because the blood within these veins is observed through the layers of the skin and the subcutaneous tissue.

Erythrocyte Life Cycle • No organelles, therefore can not sustain itself. • Finite life span of about 120 days. • Daily: – About 1% of oldest RBCs are removed • Are phagocytized by liver and spleen. – By macrophages • Some components saved, some discarded

Blood Types • Determined by membrane proteins in the RBC cell membrane. • Called surface antigens (agglutinogens). • Most common group: ABO blood group – Two antigens: A and B • ABO blood types: – Type A: have the A surface antigen – Type B: have the B surface antigen – Type AB: have both the A and the B surface antigens – Type O: have neither the A or the B surface antigen.

Blood Types • Antibodies (agglutinins) to the surface antigens are in the plasma • ABO group has anti-A antibodies and anti-B antibodies – – Type A: have anti-B Type B: have anti-A Type AB: has neither anti-A or anti-B Type O: has both anti-A and anti- B

White Blood Cells • leukocytes • protect against disease • interleukins and colony-stimulating factors stimulate development • granulocytes • neutrophils • eosinophils • basophils • agranulocytes • lymphocytes • monocytes

Platelets • Irregular, membrane-enclosed cellular fragments – about 2 micrometers in diameter (less than onefourth the size of an erythrocyte). • Sometimes called thrombocytes. • Continually produced in the red bone marrow by cells called megakaryocytes.

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