Chapter 12 Circulatory System Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 1 Pretest 1.The pointed end of the heart is the apex. 2.The myocardium forms the bulk of the heart wall. 3.The coronary arteries branch off the aorta to supply the heart with oxygen and nutrients. 4.The SA node is located in the right atrium. 5.The adult male has 5-6 liters of blood. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 2 True or False Pretest, cont. 6.Erythrocytes lack a nucleus. 7.Vitamin K is necessary for the absorption of vitamin B 12 from the intestines. 8.Leukocytes defend the body against disease. 9.Thrombocytes develop from large cells known as macrophages. 10.Veins carry blood toward the heart. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 3 True or False Introduction to the Circulatory System Made up of: Heart: central pump Blood vessels: moves blood through body Blood: transport medium Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 4 Introduction to the Circulatory System, cont. The Heart Muscular pump Provides the force necessary to circulate blood to all tissues in body Tissues need a continuous supply of oxygen and nutrients Metabolic waste products: must be removed Pumps 5 liters of blood every minute Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 5 Overview of the Heart Located in thoracic cavity between the lungs Posterior to sternum Anterior to vertebral column Two thirds of heart mass: to the left of bodys midline (one third is to the right) 3.Apex: pointed end of heart Extends downward to level of fifth intercostal space Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 6 Form, Size, and Location of the Heart Overview of the Heart, cont. 4.Base: opposite end Larger and less pointed than apex Has several large vessels attached to it 5.Size of heart: varies with size of individual Average: 9 cm wide and 12 cm long (size of a closed fist) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 7 Overview of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 8 From Jarvis C: Physical examination and health assessment, ed 4, St. Louis, 2004, Saunders Overview of the Heart, cont. 1.Pericardium: loose-fitting, double-layered sac that encloses the heart consisting of: a.Fibrous pericardium: outer layer of pericardium Consists of tough, white fibrous connective tissue b.Parietal pericardium: serous membrane that lines the fibrous pericardium c.Visceral pericardium: parietal pericardium reflects back onto the surface of the heart to form the visceral pericardium Also called epicardium Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 9 Coverings of the Heart Overview of the Heart, cont. 2.Pericardial cavity: small space between parietal and visceral layers of pericardium Contains a thin layer of serous fluid Reduces friction between the membranes as they rub against each other during heart contractions Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 10 Overview of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 11 Structure of the Heart 1.Epicardium (same as the visceral pericardium): consists of a serous membrane Thin protective layer: firmly anchored to underlying muscle Contains blood vessels: nourish heart wall 2.Myocardium: forms bulk of heart wall Composed of cardiac muscle tissue Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 12 Layers of the Heart Wall Structure of the Heart, cont. b.Contraction of myocardium: Provides force that ejects blood from heart and moves it through vessels c.Endocardium: smooth inner lining of heart wall Permits blood to move easily through heart Also forms the valves of the heart Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 13 Structure of the Heart, cont. 1.Four chambers: Right atrium Right ventricle Left atrium Left ventricle Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 14 Chambers of the Heart Structure of the Heart, cont. 2.Atria: thin-walled chambers Receive blood from the veins 3.Ventricles: thick-walled chambers Forcefully pump blood out of the heart Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 15 Structure of the Heart, cont. 4.Right atrium: receives deoxygenated blood From superior vena cava and inferior vena cava Superior vena cava: returns blood to heart From head, neck, and upper extremities Inferior vena cava: returns blood to heart From thorax, abdomen, pelvis, and lower extremities Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 16 Structure of the Heart, cont. 5.Left atrium: receives oxygenated blood From lungs through four pulmonary veins 6.Interatrial septum: partition that separates right and left atria Fossa ovalis: thin region in the septum Represents an opening (foramen ovale) that is present between the atria in the fetal heart Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 17 Structure of the Heart, cont. 7.Right ventricle: receives blood from the right atrium Pumps it to lungs, where it picks up oxygen 8.Left ventricle: receives blood from left atrium Pumps it to tissues of body 9.Interventricular septum: thick, muscular partition between the right and left ventricles Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 18 Structure of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 19 From Jarvis C: Physical examination and health assessment, ed 4, St. Louis, 2004, Saunders Structure of the Heart, cont. Valves of the Heart 1.Atrioventricular (AV) valves Permit the flow of blood from atria into corresponding ventricle Prevent backflow of blood from ventricles into atria Consist of a fibrous connective tissue ring and double folds of endocardium Form the cusps of the valve Attached to papillary muscles in the ventricles by chordae tendineae Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 20 Structure of the Heart, cont. d.Tricuspid valve: between right atrium and right ventricle Has three cusps e.Bicuspid (mitral) valve: between left atrium and left ventricle Has two cusps Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 21 Structure of the Heart, cont. 2.Semilunar (SL) valves Located at the bases of the large vessels that carry blood from the ventricles Each valve consists of three cuplike cusps Prevent the flow of blood back into the ventricles d.Pulmonary SL valve: located at the exit of the right ventricle In the base of the pulmonary trunk e.Aortic SL valve: located at the exit of the left ventricle In the base of the aorta Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 22 Structure of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 23 Structure of the Heart, cont. Both atria contract at the same time Both ventricles contract at the same time Heart functions as two pumps: Pulmonary circulation: pump on the right side Pumps blood to lungs Systemic circulation: pump on the left side Pumps blood to rest of body Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 24 Pathway of Blood through the Heart Structure of the Heart, cont. 4.Blood flow through the heart Blood enters right atrium through superior vena cava and inferior vena cava Low in oxygen and high in carbon dioxide Flows through tricuspid valve into right ventricle Passes through pulmonary SL valve Flows into pulmonary trunk and into pulmonary arteries Blood carried to lungs Carbon dioxide is released and oxygen is picked up Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 25 Structure of the Heart, cont. g.Pulmonary veins carry blood to left atrium h.Blood flows through bicuspid valve into left ventricle i.Flows through aortic SL valve into aorta j.Distributed to all parts of the body through the systemic circulation Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 26 Structure of the Heart, cont. Myocardium: needs a continuous supply of oxygen and nutrients Has an extensive network of blood vessels Two coronary arteries: branch from aorta a.Right and left coronary arteries Have numerous branches Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 27 Blood Supply to the Myocardium Physiology of the Heart Functions: Pump blood to the lungs through the pulmonary circulation Pump blood to the rest of the body through the systemic circulation Accomplished by contraction and relaxation of the cardiac muscle in the myocardium Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 28 Physiology of the Heart, cont. Components of the Conduction System Sinoatrial node (SA node) Located in the right atrium: near entrance of superior vena cava Initiates impulses: without neural stimulation times per minute Establishes basic rhythm of the heartbeat Called the pacemaker of the heart Impulses travel throughout atrial myocardium Cause atria to contract simultaneously Impulses reach AV node Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 29 Conduction System Physiology of the Heart, cont. 2.Atrioventricular Node (AV node) Located in floor of right atrium: near interatrial septum Cells in the AV node: conduct impulses more slowly Causes brief delay as impulses travel through the node Allows time for atria to finish contracting before the ventricles begin contracting Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 30 Physiology of the Heart, cont. 3.Atrioventricular bundle, bundle branches, and conduction myofibers From AV node: Impulses travel through AV bundle (bundle of His) to right and left bundle branches Bundle branches Extend along the right and left sides of the interventricular septum Branch profusely to form conduction myofibers (Purkinje fibers) Conduction myofibers: transmit impulses to myocardium Cause ventricles to contract simultaneously Blood is forced out through SL valves into aorta Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 31 Physiology of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 32 Physiology of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc Consists of one heartbeat a.Two atria contract at same time b.Then relax while two ventricles contract Cardiac Cycle Physiology of the Heart, cont. 2.With a heart rate of 75 beats per minute, one cardiac cycle lasts 0.8 second a.Atrial systole: contraction of the atria (0.1 second) AV valves are open Ventricles are in diastole (relaxed) Blood is forced into ventricles Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 34 Physiology of the Heart, cont. b.Ventricular systole: contraction of ventricles (0.3 second) Atria are in diastole (relaxed) Are filling with blood returned through venae cavae c.All chambers are in simultaneous diastole (0.4 second) 70% of ventricular filling occurs during this period Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 35 Physiology of the Heart, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc First heart sound: lubb a.Caused by closure of AV valves 2.Second heart sound: dupp a.Caused by closure of SL valves 3.Pause between dupp of the first beat and lubb of second beat a.Entire heart is resting 4.Abnormal heart sounds: murmurs a.Caused by faulty valves Heart Sounds Blood Primary transport medium Provides cells with nutrients and oxygen Removes metabolic wastes Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 37 Functions and Characteristics of the Blood Connective tissue Consists of cells and cell fragments (formed elements) suspended in an intercellular matrix (plasma) Blood is the only liquid tissue in the body Blood volume in an average adult: Female: 4-5 liters Male: 5-6 liters Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 38 Functions and Characteristics of the Blood, cont. 5.Functions: a.Transportation Carries oxygen and nutrients to cells Transports carbon dioxide and nitrogenous wastes From the tissues to the lungs and kidneys Carries hormones from endocrine glands to target tissues Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 39 Functions and Characteristics of the Blood, cont. b.Regulation Regulates body temperature Removes heat from skeletal muscles: 1)Transports it to other regions 2)Transports it to skin, where it can be dissipated Fluid and electrolyte balance Salts and plasma proteins contribute to the osmotic pressure pH regulation through the action of buffers in the blood Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 40 Functions and Characteristics of the Blood, cont. c.Protection Clotting mechanisms: prevent fluid loss through hemorrhage When blood vessels are damaged Phagocytic white blood cells Help protect against microorganisms Antibodies in the plasma Help protect against disease Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 41 Composition of the Blood Plasma: 55% of blood volume Red blood cells: 45% of blood volume Buffy coat: consists of WBCs and platelets Forms a thin white layer between the plasma and RBCs Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 42 Composition of the Blood, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 43 Composition of the Blood, cont. Plasma Liquid portion of the blood 90% water Remaining portion: approximately 100 different organic and inorganic solutes Plasma Proteins Most abundant solute Remain in blood and interstitial fluid Are not used for energy Many are synthesized in liver Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 44 Composition of the Blood, cont. 4.Types a.Albumins 60% of plasma proteins Produced in liver Contribute to osmotic pressure of blood Play role in maintaining fluid balance between blood and interstitial fluid Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 45 Composition of the Blood, cont. If the osmotic pressure of blood decreases, fluid moves from blood into interstitial spaces 1)Results in edema 2)Decreases blood volume 3)In severe cases: may reduce blood pressure If blood osmotic pressure increases: fluid moves from interstitial spaces into blood 1)Increases blood volume 2)Increases blood pressure 3)Decreases amount of water available to cells Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 46 Composition of the Blood, cont. b.Globulins 36% of the plasma proteins Three types: Alpha and beta globulins: produced in the liver 1)Transport lipids and fat-soluble vitamins in blood Gamma globulins: produced in lymphoid tissue 1)Are antibodies that function in immunity Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 47 Composition of the Blood, cont. c.Fibrinogen 4% of plasma proteins Produced in liver Functions in blood clotting During clotting process: soluble fibrinogen is converted into insoluble fibrin 1)Forms the foundation of a blood clot When blood clots in a test tube, liquid that remains is called serum 1)Similar to plasma 2)But has no fibrinogen (fibrinogen is converted to fibrin) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 48 Composition of the Blood, cont. Nonprotein Molecules That Contain Nitrogen Plasma solutes that contain nitrogen Amino acids: products of protein digestion Absorbed into blood Transported to cells that need them Urea and uric acid: waste products of protein and nucleic acid catabolism Transported to the kidneys for excretion Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 49 Composition of the Blood, cont. Nutrients and Gases 1.Simple nutrients: end products of digestion Transported in the blood Include: Amino acids: from protein digestion Glucose and other simple sugars: from carbohydrate digestion Fatty acids: from lipid digestion Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 50 Composition of the Blood, cont. 2.Respiratory gases Oxygen and carbon dioxide 3% of oxygen and 7%-10% of carbon dioxide Transported as dissolved gases Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 51 Composition of the Blood, cont. Electrolytes Inorganic ions Contribute to osmotic pressure of plasma Common electrolytes in plasma: Sodium (Na + ) Potassium (K + ) Calcium (Ca ++ ) Chloride (Cl - ) Bicarbonate (HCO 3 - ) Phosphate (PO 4 -3 ) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 52 Composition of the Blood, cont. 1.Erythrocytes: red blood cells 2.Leukocytes: white blood cells 3.Thrombocytes: platelets Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 53 Formed Elements Composition of the Blood, cont. 4.Hematopoiesis: production of blood cells Before birth: occurs primarily in liver and spleen After birth: Red bone marrow in specific regions of body Some WBCs are produced in lymphoid tissue c.Hemocytoblast: a stem cell in the bone marrow from which blood cells develop Seven different cell lines develop from the hemocytoblast Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 54 Composition of the Blood, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 55 Composition of the Blood, cont. Erythrocytes Characteristics and functions of RBCs Most numerous of formed elements RBC range for adult: Female: million RBCs/cubic millimeter (mm 3 ) of blood Male: million RBCs/cubic millimeter (mm 3 ) of blood Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 56 Composition of the Blood, cont. c.Biconcave disks: thin in middle and thicker around periphery Provide flexibility for moving through capillaries Provide maximum surface area for diffusion of gases d.Mature RBCs: do not have a nucleus (anucleate) During development: nucleus is lost from cell Gives cell more room for hemoglobin Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 57 Composition of the Blood, cont. e.Develop from stem cells in red bone marrow Move from bone marrow into blood while still immature Reticulocyte: immature erythrocyte f.Functions: of erythrocytes: Transport oxygen and, to a lesser extent, carbon dioxide Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 58 Composition of the Blood, cont. g.Hemoglobin Makes up one third of each erythrocyte Consists of two parts: Heme: formed from a pigment that contains iron Globin: protein Heme combines with oxygen in the lungs: oxyhemoglobin Bright red Oxygen is released to diffuse into tissue cells: deoxyhemoglobin Darker red in color Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 59 Composition of the Blood, cont. 2.Production of erythrocytes Negative feedback mechanism b.Erythropoietin: stimulates erythrocyte production c.Liver produces erythropoietin in inactive form Secretes it into blood Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 60 Composition of the Blood, cont. d.Renal erythropoietic factor (REF): activates erythropoietin e.When blood oxygen concentration is low: Kidneys release REF into blood Activates erythropoietin f.Stimulates red bone marrow to produce RBCs g.Additional RBCs: combine with oxygen Increases blood oxygen concentration h.As blood oxygen concentration increases: Levels of REF and active erythropoietin decrease RBC production decreases Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 61 Composition of the Blood, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 62 Composition of the Blood, cont. i.Needed for RBC production: Iron Vitamin B 12 Folic acid Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 63 Composition of the Blood, cont. j.Intrinsic factor: Produced by stomach Needed for absorption of vitamin B 12 in the intestines Without intrinsic factor: vitamin B 12 cannot be absorbed Results in pernicious anemia Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 64 Composition of the Blood, cont. 3.Destruction of erythrocytes Lifespan of an erythrocyte: 120 days As erythrocyte ages: Cell membrane becomes fragile Macrophages (phagocytic cells in spleen and liver) remove them from circulation Replaced by an equal number of new cells 2 million erythrocytes are destroyed and replaced every second Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 65 Composition of the Blood, cont. e.Hemoglobin separates into heme and globulin: Heme broken down into: Iron compound: used to make new hemoglobin Bilirubin: yellow bile pigment 1)Becomes part of bile Globin (protein) Broken down into amino acids: added to supply of amino acids available in body Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 66 Composition of the Blood, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 67 Composition of the Blood, cont. Leukocytes Characteristics and functions of WBCs Larger than erythrocytes Fewer in number Normal WBC count: 4,500-11,000 cells/mm 3 Derived from hemocytoblast stem cells Do not lose their nuclei Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 68 Composition of the Blood, cont. e.Leukocytes do most of their work in the tissues Use blood as transport medium Move through capillary walls into tissue spaces: diapedesis f.Provide a defense against organisms that cause disease Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 69 Composition of the Blood, cont. Types of Leukocytes 1.Granular leukocytes (granulocytes): granules in the cytoplasm a.Neutrophils Normal range: 50%-70% of WBCs Purple, multilobed nucleus (3-5 lobes) Many fine granules in cytoplasm Stain violet-pink Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 70 Composition of the Blood, cont. Band: immature neutrophil Curved, nonsegmented nuclei 0%-5% of neutrophils: normally present in band form First leukocytes to respond to tissue damage Engulf bacteria by phagocytosis Neutrophils and bands: increase during acute infections Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 71 Composition of the Blood, cont. b.Eosinophils Normal range: 1%-4% of WBCs Segmented nucleus (no more than two lobes) Large granules in the cytoplasm: stain bright reddish orange Functions: Neutralize histamine 1)Number increases during allergic reactions Destroy parasitic worms Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 72 Composition of the Blood, cont. c.Basophils Normal range: 0%-1% of WBCs S-shaped nucleus Large, coarse granules in cytoplasms Stain dark bluish-black Almost completely obscure details of nucleus Secrete histamine and heparin Histamine: dilates blood vessels 1)Increases blood flow to damaged tissues 2)Dilates blood vessels in allergic reactions Heparin: inhibits blood clot formation Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 73 Composition of the Blood, cont. 2.Nongranular leukocytes (agranulocytes): no granules in the cytoplasm a.Lymphocytes Normal range: 20%-35% of WBCs Large round or slightly indented nucleus Stains a deep purplish blue Small rim of sky-blue cytoplasm around nucleus Produces antibodies Increase in lymphocytes: occurs with certain viral diseases Infectious mononucleosis, mumps, chickenpox, rubella, viral hepatitis Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 74 Composition of the Blood, cont. b.Monocytes Largest WBC Normal range: 3%-8% of WBCs U-shaped or kidney-shaped nucleus Surrounded by abundant cytoplasm: stains grayish-blue Macrophages: monocytes that leave the blood and enter the tissues Engulf bacteria and cellular debris Finishes the cleanup process started by neutrophils Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 75 Composition of the Blood, cont. Thrombocytes Also known as platelets Consist of small fragments of large cells: megakaryocytes Develop from hemocytoblasts in red bone marrow Normal range: 150,000 to 500,000 platelets/mm 3 of blood Functions: Close breaks in blood vessels Become sticky and clump together to form platelet plugs Initiate the formation of blood clots Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 76 Hemostasis Blood vessels that are torn or cut: permit blood to escape Into surrounding tissues or to outside of the body Excessive blood loss: may result in death Injured blood vessels: trigger reactions to minimize blood loss and tissue damage 3.Hemostasis: the stoppage of bleeding Consists of three processes: Vascular constriction Platelet plug formation Coagulation Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 77 Hemostasis, cont. First response to blood vessel injury Contraction of smooth muscle in vessel walls (constriction) Restricts flow of blood through opening in the vessel Lasts only a few minutes Allows enough time for other aspects of hemostasis to begin 3.Platelets secrete a chemical: serotonin Stimulates smooth muscle contraction in vessel wall Prolongs the vascular constriction Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 78 Vascular Constriction Hemostasis, cont. Platelet Plug Formation Normally platelets do not: Stick to each other Stick to blood vessel walls When blood vessel breaks: Underlying connective tissue is exposed Attracts platelets Accumulate in damaged region Adhere to connective tissue and each other Creates a platelet plug Obstructs tear in the vessel Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 79 Hemostasis, cont. Formation of a blood clot 2.Procoagulants: factors in the blood that promote clotting 3.Anticoagulants: factors in the blood that inhibit clotting 4.Normally anticoagulants override procoagulants Blood remains fluid and does not clot 5.When vessels damaged: procoagulants increase activity Results in the formation of a clot Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 80 Coagulation Hemostasis, cont. 6.Involves a series of chemical reactions Platelets and damaged tissues release chemicals Initiate a series of reactions: result in formation of prothrombin activator In the presence of calcium ions and prothrombin activator: Prothrombin (inactive) is converted thrombin (active) Thrombin converts fibrinogen (inactive) fibrin (active) Fibrin threads: form a mesh Adheres to damaged tissue Traps blood cells and platelets to form the clot Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 81 Hemostasis, cont. 7.After a clot has formed: Fibrin strands contract: clot retraction Causes clot to shrink Pulls edges of damaged tissue closer together Reduces blood flow to area Reduces probability of infection Enhances healing Fibroblasts migrate into clot Form fibrous connective tissue Repairs damaged area 8.Clot is eventually dissolved: fibrinolysis Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 82 Blood Types ABO Blood Groups Based on the presence or absence of certain antigens On the surface of RBC membrane Blood types are inherited Blood types: Type A: A antigen Type B: B antigen Type AB: A and B antigens Type O: neither A nor B antigens Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 83 Blood Types, cont. 4.Certain blood antibodies: develop in plasma shortly after birth Type A blood: B antibodies Type B blood: A antibodies Type AB blood: Neither A nor B antibodies Type O blood: A and B antibodies Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 84 Blood Types, cont. First studied in rhesus monkey Rh positive (Rh+): Rh antigen 85% of population Rh negative (Rh-): do not have Rh antigen 15% of population Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 85 Rh Blood Groups Blood Types, cont. 4.Inherited trait 5.Normally: neither Rh+ nor Rh- individuals have Rh antibodies If Rh- person is exposed to Rh+ blood (through blood transfusion or transfer of blood between a mother and fetus) Individual develops Rh antibodies If exposed to Rh+ blood a second time: Transfusion reaction results Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 86 Blood Vessels Channels through which blood is distributed to body tissues Pulmonary vessels: transport blood from right ventricle to lungs and back to left atrium Systemic vessels: carry blood from left ventricle to all parts of the body and then return it to right atrium Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 87 Blood Vessels, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 88 Classification and Structure of Blood Vessels Carry blood away from heart 2.Pulmonary arteries: transport blood that has a low oxygen content From right ventricle to lungs 3.Systemic arteries: transport oxygenated blood from left ventricle to body tissues 4.Blood is pumped from ventricles into large elastic arteries Branch repeatedly into smaller arteries Branching results in microscopic arteries: arterioles Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 89 Arteries Classification and Structure of Blood Vessels, cont. 5.Artery wall a.Tunica intima: innermost layer b.Tunica media: middle layer Consists of smooth muscle Usually the thickest layer Provides support for the vessel Changes vessel diameter To regulate blood flow and blood pressure c.Tunica externa: outermost layer Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 90 Classification and Structure of Blood Vessels, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 91 Classification and Structure of Blood Vessels, cont. Smallest and most numerous of the blood vessels Form connection between: Vessels that carry blood away from the heart (arteries) Vessels that return blood to heart (veins) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 92 Capillaries Classification and Structure of Blood Vessels, cont. 3.Capillary wall: consists of a thin endothelium (one cell layer) Permits exchange of materials between: Blood in the capillary Adjacent tissue cells 4.Capillary is so small: erythrocytes must pass through them in single file Slows blood flow Allows time for transport of substances across capillary endothelium Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 93 Classification and Structure of Blood Vessels, cont. Carry blood toward heart After blood passes through capillaries: Enters the smallest veins: venules Flows into progressively larger veins until reaches the heart Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 94 Veins Classification and Structure of Blood Vessels, cont. 3.Vein walls: same three layers as the arteries Less smooth muscle and connective tissue Makes walls of veins thinner and less rigid than those of arteries Blood in the veins has less pressure than blood in the arteries Veins can hold more blood: holds 70% of the total blood volume 4.Venous valves: located in medium and large veins Keep blood flowing toward heart Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 95 Circulatory Pathways The blood vessels of the body are functionally divided into two distinct circuits: Pulmonary circuit Systemic circuit Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 96 Circulatory Pathways, cont. Transports blood from right side of the heart to lungs Then returns it to left side of heart Contains oxygen-poor blood (increased levels of carbon dioxide) Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 97 Pulmonary Circuit Circulatory Pathways, cont. 3.Pathway for pulmonary circuit Blood is returned to right atrium from the tissue cells of the body Blood passes through tricuspid valve into right ventricle During ventricular systole: blood is ejected through pulmonary SL valve Into pulmonary trunk: divides into right and left pulmonary arteries Each pulmonary artery enters a lung Divides into smaller vessels until they become capillaries Capillaries of the lungs: form networks Surround the air sacs: alveoli Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 98 Circulatory Pathways, cont. f.CO 2 diffuses from capillary blood into alveoli g.O 2 diffuses from alveoli into blood h.Oxygenated blood enters pulmonary venules Form progressively larger veins Until two pulmonary veins emerge from each lung i.Blood is carried to left atrium 4.In pulmonary circuit: Arteries carry deoxygenated blood away from heart Veins carry oxygenated blood to heart Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 99 Circulatory Pathways, cont. Provides blood supply to all body tissues Carries oxygen and nutrients to cells Picks up carbon dioxide and waste products Carries oxygenated blood from left ventricle through the arteries to the capillaries in the tissues From tissue capillaries: deoxygenated blood returns through a system of veins to right atrium Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 100 Systemic Circuit Circulatory Pathways, cont. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 101 Posttest The peritoneum is the loose-fitting sac that encloses the heart. The superior vena cava returns blood to the heart from the lower extremities. The mitral valve is located between the right atrium and right ventricle. When the ventricles are contracting, the AV valves are open. The buffy coat is made up of white blood cells and platelets. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 102 True or False Posttest, cont. 6.An immature erythrocyte is a band. 7.Bile is the yellow pigment that results from the breakdown of hemoglobin. 8.Acute infections cause an increase in the number of neutrophils. 9.Thrombin converts fibrinogen to fibrin. 10.Microscopic arteries are known as arterioles. Elsevier items and derived items 2009 by Saunders, an imprint of Elsevier Inc. 103 True or False