NS 3410 1st Edition Lecture 16Outline of Last LectureI. General Rules of Thumb- Clinical InformationII. Skeletal SystemIII. Classification of BonesOutline of Current LectureI. BloodII. Erythrocytes (RBCs)III. ErythropoiesisIV. AnemiaCurrent LectureI. Blood- Functions of blood:-Transports gases, nutrients, hormones, cytokines, heat, waste-Maintains appropriate body temperature, normal pH in body tissues using buffer systems, adequate fluid volume in the circulatory system, renews and replenishes interstitial fluid-Utilizes mechanisms to protect against blood loss by: activating plasma proteins and platelets, initiating clot formation when a vessel is broken-Prevents infection by synthesizing and utilizing antibodies, activating WBCs to defend the body against foreign invaders- Components of blood: -Formed elements: erythrocytes (RBCs), leukocytes (WBCs), platelets-PlasmaThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Hematocrit= % of whole blood volume contributed by formal elements (avg adult is 45%) -Average adult blood volume is 5 liters- Composition of blood:-Plasma: 91% is water, 7% proteins, other solutes 2%-Formed elements: RBC 95%, also contains platelets and WBCs (neutrophils make up majority of WBCs)II. Erythrocytes (RBCs)- Main function of RBCs is to carry oxygen- They lose their nuclei and other organelles during differentiation- Advantages of biconcave disc shape:-Large surface area-to-volume ratio: enables oxygen to diffuse rapidly between the exterior and innermost regions of the cell-Allows RBCs to form stacks (rouleaux): allows smooth flow through narrow capillaries-Flexible membrane: allows RBCs to travel through narrow capillaries without rupturing the process- Hemoglobin is found only in red blood cells. Heme is non-protein pigment containing iron. It appears reddish when oxygenated and bluish when deoxygenated- Hemoglobin consists of two parts:-Globin portion: protein composed of four highly folded polypeptide chains-Heme groups (bind oxygen): four iron-containing nonprotein groups. Each is bound to one of the polypeptides-Organic ring is called a porphyrin; contains Fe at its center-Each Hb molecule can transport 4 molecules of oxygen- Oxyhemoglobin: Hb bound to oxygen; oxygen loading takes place in the lungs- Deoxyhemoglobin: Hb after oxygen diffuses into tissues- Carbaminohemoglobin: Hb bound to carbon dioxide -Carbon dioxide loading takes place in the tissues-Carbon dioxide binds to the amino acids on globin- not to the heme group-Can bind more readily when hemoglobin is dissociated from oxygenIII. Erythropoiesis- This is the process of forming new RBCs- RBCs survive about 120 days- Macrophages of the spleen, liver, and bone marrow remove old erythrocytes from circulation- Must be replaced at rate of 2 million to 3 million cells/second- Occurs in red bone marrow-In adults: in bones of axial skeleton and girdles and in proximal epiphyses of the humerus and femur-Hemocytoblasts: in red bone marrow differentiate into the different type of blood cells- Day 1: proerythroblast, Day 2 and 3: erythroblast, Day 4: normoblast, Days 5-7: reticulocyte. Ejection of nucleus occurs at day 4. After day 7 get a mature red blood cell- Extramedullary erythropoiesis: if have some diseases erythropoiesis can occur outside the bone marrow- Control of erythropoiesis: -Kidneys detect decrease in oxygen-Kidneys secrete EPO-EPO stimulates erythropoiesis by bone marrow-RBCs increase and oxygen carrying increases-Relieves initial stimulus and decreases EPO secretion - Old RBCs become rigid and fragile and their HB begins to degenerate- Under normal conditions RBC production and destruction are maintained at the same pace- Dying RBCs are engulfed by macrophages- Heme and globin are separated and the iron is salvaged for reuse- RBC become trapped in small circulatory channels, especially in those of the spleen- The spleen has two main functions: destruction of old RBCs and mounting an immune response- Spleen has red pulp, which consists of clusters of macrophages and RBCs and white pulp which consists of lymphocytes suspended on reticular fibers- Blood entering the spleen travels through progressively smaller arterioles until it is deposited in an area known as the red pulp. This is where the senescent RBCs are destroyed (extravascular destruction). The immune reactivity of the spleen is especially effective for dealing with blood-borne antigens such as bacteria that reach the blood- Invascular destruction: destruction of RBC in circulation; less than 10% of RBC- Events occurring in macrophages:-Fe transported in circulation by transferrin-Heme > biliverdin> bilirubin; bilirubin bound to albumin in bloodstream. If liver can’t excrete bilirubin, it diffuses into peripheral tissues and gives skin a yellow color= jaundice-Hb that is not phagocytized breaks down and the alpha and beta chains are eliminated in urine- Hemoglobinuria= if large numbers of RBC break down the urine may turn red or brown; may get when have hemolytic anemia- Hematuria= intact RBCs in the urine; only occurs if kidney damage or damage to vessels in the urinary tract- Free heme in blood binds to a carrier protein hemopexin and free Hb in blood binds to haptoglobinIV. Anemia- Characterized by below-normal oxygen-carrying capacity of the blood- Characterized by a low hematocrit- 6 types-Nutritional: dietary deficiency of a factor-Pernicious: inability to absorb vitamin B12-Aplastic: failure of marrow to produce RBCs-Renal: inadequate secretion of EPO-Hemorrhagic: severe loss of blood-Hemolytic: rupture of too many RBCs- Polycythemia: elevated concentration of hemoglobin generally due to bone marrow making too many