Obj 1 Blood 1 (2).pdf PDF

PN 1241 Chp. 17 Objective 1: Blood 1 Objectives 1. Discuss the structure and function of the blood. 1.1 Define key terms related to the blood. 1.2 Discuss the primary functions of the blood. 1.3 Discuss the two prime elements of the blood. 1.4 Discuss the three-formed elements of the blood and their...

PN 1241 Chp. 17 Objective 1: Blood 1 Objectives 1. Discuss the structure and function of the blood. 1.1 Define key terms related to the blood. 1.2 Discuss the primary functions of the blood. 1.3 Discuss the two prime elements of the blood. 1.4 Discuss the three-formed elements of the blood and their most important functions. 1.5 Discuss the components of blood plasma. 1.6 Discuss the three steps in hemostasis 1.7 Discuss the steps in blood clotting. 1.8 Identify the four blood types and their characteristics. 1.9 Discuss Rh factor including Rh positive and Rh-negative blood. 2 Functions of Blood ⦁ Blood is the life-sustaining transport vehicle of the cardiovascular system ⦁ Functions include: ⦁ Transport ⦁ Regulation ⦁ Protection © 2016 Pearson Education, Inc. Transport ⦁ Transport functions include: ⦁ Delivering O2 and nutrients to body cells ⦁ Transporting metabolic wastes to lungs and kidneys for elimination ⦁ Transporting hormones from endocrine organs to target organs © 2016 Pearson Education, Inc. Regulation ⦁ Regulation functions include: ⦁ Maintaining body temperature by absorbing and distributing heat ⦁ Maintaining normal pH using buffers ⦁ Maintaining adequate fluid volume in circulatory system © 2016 Pearson Education, Inc. Protection ⦁ Protection functions include: ⦁ Preventing blood loss ⦁ Plasma proteins and platelets in blood initiate clot formation ⦁ Preventing infection ⦁ Agents of immunity are carried in blood Antibodies Complement proteins White blood cells © 2016 Pearson Education, Inc. Composition of Blood ⦁ Blood is the only fluid tissue in body ⦁ A type of connective tissue ⦁ Matrix is nonliving fluid called plasma ⦁ Contains living blood cells called formed elements ⦁ Cells are suspended in plasma ⦁ Formed elements Erythrocytes (red blood cells, or RBCs) Leukocytes (white blood cells, or WBCs) Platelets (clotting) © 2016 Pearson Education, Inc. Composition of Blood ⦁ Spun tube of blood yields three layers: ⦁ Erythrocytes on bottom (~45% of whole blood) ⦁ Hematocrit: percent of blood volume that is RBCs Normal values: ○ Males: 47% ± 5% ○ Females: 42% ± 5% ⦁ WBCs and platelets in Buffy coat layer(< 1%) ⦁ Thin, whitish layer between RBCs and plasma layers ⦁ Plasma on top (~55%) © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc 9 9 Physical Characteristics and Volume ⦁ Blood is a sticky, opaque fluid with metallic taste ⦁ Color varies with O2 content ⦁ High O2 levels show a scarlet red ⦁ Low O2 levels show a dark red ⦁ pH 7.35–7.45 ⦁ Makes up ~8% of body weight ⦁ Average volume: ⦁ Males: 5–6 L ⦁ Females: 4–5 L © 2016 Pearson Education, Inc. Blood Plasma ⦁ Blood plasma is straw-colored sticky fluid ⦁ About 90% water ⦁ Over 100 dissolved solutes (10%) ⦁ Nutrients, gases, hormones, wastes, proteins, inorganic ions ⦁ Plasma proteins are most abundant solutes ⦁ Remain in blood; not taken up by cells to be used as fuel ⦁ Proteins produced mostly by liver ⦁ Albumin: makes up 60% of plasma proteins Functions as carrier of other molecules, as blood buffer, and contributes to plasma osmotic pressure © 2016 Pearson Education, Inc. Formed Elements ⦁ Formed elements are RBCs, WBCs, and platelets ⦁ Only WBCs are complete cells ⦁ RBCs have no nuclei or other organelles ⦁ Platelets are cell fragments ⦁ Most formed elements survive in bloodstream only few days ⦁ Most blood cells originate in bone marrow and do not divide © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. Figure 17.2a Blood cells. Leukocytes Erythrocytes Platelets SEM of blood (1800, artificially colored) Erythrocytes Structural Characteristics ⦁ ⦁ ⦁ ⦁ ⦁ ⦁ ⦁ Erythrocytes are small (7.5 m) cells that contribute to gas transport biconcave disc shape anucleate no organelles Filled with hemoglobin (Hgb) for gas transport RBC diameters are larger than some capillaries Contain plasma membrane protein spectrin ⦁ Spectrin provides flexibility to change shape to pass through capillaries Structural Characteristics (cont.) ⦁ Superb example of complementarity of structure and function ⦁ Three features make for efficient gas transport: ⦁ Biconcave shape offers huge surface area for gas exchange ⦁ Hemoglobin makes up 97% of cell volume (not counting water) ⦁ RBCs have no mitochondria ⦁ ATP production is anaerobic, so they do not consume O2 they transport © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. Figure 17.3 Structure of erythrocytes (red blood cells). 2.5 m Side view (cut) 7.5 m Top view Function of Erythrocytes ⦁ RBCs are dedicated to respiratory gas transport ⦁ Hemoglobin binds reversibly with oxygen ⦁ Normal Hgb values: Males 13–18g/100ml; Females: 12–16 g/100ml ⦁ Hemoglobin consists of red heme pigment bound to the protein globin ⦁ Globin is composed of four polypeptide chains ⦁ Two alpha and two beta chains ⦁ A heme pigment is bonded to each globin chain ⦁ Gives blood red color ⦁ Each heme’s central iron atom binds one O2 © 2016 Pearson Education, Inc. Function of Erythrocytes (cont.) ⦁ Each Hgb molecule can transport four O2 ⦁ Each RBC contains 250 million Hgb molecules ⦁ O2 loading in lungs to bring O2 to body tissues ⦁ Produces oxyhemoglobin when O2 binds with iron(ruby red) ⦁ O2 unloading in tissues ⦁ Produces deoxyhemoglobin, or reduced hemoglobin (dark red) ⦁ CO2 loading in tissues ⦁ 20% of CO2 in blood binds to globins amino acid rather than the heme, producing carbaminohemoglobin © 2016 Pearson Education, Inc. Production of Erythrocytes ⦁ Hematopoiesis: formation of all blood cells ⦁ Occurs in red bone marrow ⦁ In adult, found in axial skeleton, girdles, and proximal epiphyses of humerus and ⦁ ⦁ femur Hematopoietic stem cells (hemocytoblasts) ⦁ Stem cell that gives rise to all formed elements ⦁ Hormones and growth factors push stem cell toward specific pathway of blood cell development ⦁ Once cells are committed to a certain blood cell pathway, it cannot change New blood cells then enter the blood stream © 2016 Pearson Education, Inc. Production of Erythrocytes (cont.) ⦁ Stages of erythropoiesis ⦁ Erythropoiesis: process of formation of RBCs that takes about 15 days ⦁ Stages of transformations: 1. Hematopoietic stem cell: transforms into myeloid stem cell (descendant of stem cell) 2. Myeloid stem cell: transforms into proerythroblast 3. Proerythroblast: divides many times, transforming into basophilic erythroblasts 4. Basophilic erythroblasts: synthesize many ribosomes © 2016 Pearson Education, Inc. Production of Erythrocytes (cont.) Stages of erythropoiesis (cont.) 5. Polychromatic erythroblasts: synthesize large amounts of red-hued hemoglobin 6. Orthochromatic erythroblasts: contain mostly hemoglobin, so appear just pink; eject most organelles; nucleus degrades, causing concave shape 7. Reticulocytes: still contain small amount of ribosomes. Differentiation occurs in bloodstream. 8. Mature erythrocyte: in 2 days, ribosomes degrade, transforming into mature RBC ⦁ Reticulocyte count indicates rate of RBC formation © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. Figure 17.5 Erythropoiesis: formation of red blood cells. Stem cell Hematopoietic stem cell (hemocytoblast) Committed cell Proerythroblas t Developmental pathway Phase 1 Ribosome synthesis Basophilic erythroblast Phase 2 Hemoglobin accumulation Polychromati c erythroblast Phase 3 Ejection of nucleus Orthochromati c erythroblasts Reticulocyt e Erythrocyt e Regulation and Requirements of Erythropoiesis ⦁ Too few RBCs lead to tissue hypoxia ⦁ Too many RBCs increase blood viscosity 9 ⦁ > 2 million RBCs are made per second ⦁ Balance between RBC production and destruction depends on: ⦁ Hormonal controls ⦁ Dietary requirements © 2016 Pearson Education, Inc. Regulation and Requirements of Erythropoiesis (cont.) ⦁ Hormonal control ⦁ Erythropoietin (EPO): hormone that stimulates formation of RBCs ⦁ Always small amount of EPO in blood to maintain basal rate ⦁ Mainly released by kidneys (some from liver) in response to hypoxia At low O2 levels, oxygen-sensitive enzymes in kidney cells cannot degrade hypoxia-inducible factor (HIF) HIF can accumulate, which triggers synthesis of EPO © 2016 Pearson Regulation and Requirements of Erythropoiesis (cont.) ⦁ Hormonal control (cont.) ⦁ Causes of hypoxia that lead to formation of EPO: ⦁ Decreased RBC numbers due to hemorrhage or increased destruction of RBC’s ⦁ Insufficient hemoglobin per RBC (example: iron deficiency) ⦁ Reduced availability of O2 (example: high altitudes or lung problems such as pneumonia) © 2016 Pearson Regulation and Requirements of Erythropoiesis (cont.) ⦁ Hormonal control (cont.) ⦁ Too many erythrocytes or high oxygen levels in blood inhibit EPO production ⦁ EPO causes erythrocytes to mature faster ⦁ Testosterone enhances EPO production, resulting in higher RBC counts in males © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. Slide 1 Figure 17.6 Erythropoietin mechanism for regulating erythropoiesis. Homeostasis: Normal blood oxygen levels 1 Stimulus: Hypoxia (inadequate O2 delivery) due to Decreased RBC count Decreased amount of hemoglobin Decreased availability of O2 5 O2-carrying ability of blood rises. 4 Enhanced erythropoiesis increases RBC count. 3 Erythropoietin stimulates red bone marrow. 2 Kidney (and liver to a smaller extent) releases erythropoietin. Regulation and Requirements of Erythropoiesis (cont.) ⦁ Dietary requirements for erythropoiesis: ⦁ Amino acids, lipids, and carbohydrates are needed ⦁ Iron: available from diet ⦁ 65% of iron is found in hemoglobin, with the rest in liver, spleen, and bone marrow ⦁ Free iron: Stored in cells as ferritin and hemosiderin Transported in blood bound to protein transferrin ⦁ Vitamin B12 and folic acid are necessary for DNA synthesis for rapidly dividing cells such as developing RBCs © 2016 Pearson Education, Inc. Fate and Destruction of Erythrocytes ⦁ Life span: 100–120 days ⦁ RBCs are anucleate, so cannot synthesize new proteins, or grow or divide ⦁ Old RBCs become fragile, and Hgb begins to degenerate ⦁ Can get trapped in smaller circulatory channels, especially in spleen ⦁ Macrophages in spleen engulf and breakdown dying RBCs © 2016 Pearson Education, Inc. Fate and Destruction of Erythrocytes (cont.) ⦁ RBC breakdown: heme, iron, and globin are separated ⦁ Iron binds to ferritin or hemosiderin and is stored to be reused later ⦁ Heme is broken down into a yellow pigment bilirubin ⦁ Liver secretes bilirubin (in bile) into intestines, where it is degraded ⦁ to pigment urobilinogen Urobilinogen is transformed into brown pigment stercobilin that leaves body in feces Globin (protein part) is metabolized into amino acids ⦁ Released into circulation summary of RBCs: https://www.visiblebody.com/learn/biology/bloodcells/blood-overview Red Blood Cells and Platelets (visiblebody.com) © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. Slide 1 1 Low O2 levels in blood stimulate kidneys to produce erythropoietin. 2 Erythropoietin levels rise in blood. 3 Erythropoietin and necessary raw materials in blood promote erythropoiesis in red bone marrow. Figure 17.7 Life cycle of red blood cells. 4 New erythrocytes enter bloodstream; function about 120 days. 5 Aged and damaged red blood cells are engulfed by macrophages of spleen, liver, and bone marrow; the hemoglobin is broken down. Hemoglobin Heme Bilirubin is picked up by the liver. Iron is stored as ferritin or hemosiderin. Globin Amino acids Iron is bound to transferrin and released to blood from liver as needed for erythropoiesis. Bilirubin is secreted into intestine in bile where it is metabolized to stercobilin by bacteria. Circulation 6 Raw materials are made available in blood for erythrocyte synthesis. Stercobilin is excreted in feces. Food nutrients (amino acids, Fe, B12, and folic acid) are absorbed from intestine and enter blood. Leukocytes ⦁ Leukocytes, or WBCs, are only formed element that are complete cells with nuclei and organelles ⦁ Make up