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Cardiovascular Overview for Home Review The basics Components of Circulatory System • Include cardiovascular & lymphatic systems – Heart pumps blood thru cardiovascular system – Blood vessels carry blood from heart to cells & back • Includes arteries, arterioles, capillaries, venules, veins • Lymphatic system picks up excess fluid filtered out in capillary beds & returns it to veins – Its lymph nodes are part of immune system 13-5 Blood 13-6 Composition of Blood • Consists of formed elements (cells) suspended & carried in plasma (fluid part) • Total blood volume is about 5L • Plasma is straw-colored liquid consisting of H20 & dissolved solutes – Includes ions, metabolites, hormones, antibodies 13-7 Plasma Proteins • Constitute 7-9% of plasma • Three types of plasma proteins: albumins, globulins, & fibrinogen – Albumin accounts for 60-80% • Creates colloid osmotic pressure that draws H20 from interstitial fluid into capillaries to maintain blood volume & pressure • Globulins carry lipids – Gamma globulins are antibodies • Fibrinogen serves as clotting factor – Converted to fibrin – Serum is fluid left when blood clots 13-8 Formed Elements • Are erythrocytes (RBCs) & leukocytes (WBCs) • RBCs are flattened biconcave discs Fig 13.3 – Shape provides increased surface area for diffusion – Lack nuclei & mitochondria – Each RBC contains 280 million hemoglobins 13-9 Leukocytes • Have nucleus, mitochondria, & amoeboid ability • Can squeeze through capillary walls (diapedesis) – Granular leukocytes help detoxify foreign substances & release heparin • Include eosinophils, basophils, & neutrophils Fig 13.3 13-10 Leukocytes continued • Agranular leukocytes are phagocytic & produce antibodies Fig 13.3 • Include lymphocytes & monocytes 13-11 Platelets (thrombocytes) • Are smallest of formed elements, lack nucleus • Are fragments of megakaryocytes; amoeboid • Constitute most of mass of blood clots • Release serotonin to vasoconstrict & reduce blood flow to clot area • Secrete growth factors to maintain integrity of blood vessel wall • Survive 5-9 days Fig 13.3 13-12 Hematopoiesis • Is formation of blood cells from stem cells in marrow (myeloid tissue) & lymphoid tissue • Erythropoiesis is formation of RBCs – Stimulated by erythropoietin (EPO) from kidney • Leukopoiesis is formation of WBCs – Stimulated by variety of cytokines • = autocrine regulators secreted by immune system 13-13 Erythropoiesis • 2.5 million RBCs are produced/sec • Lifespan of 120 days • Old RBCs removed from blood by phagocytic cells in liver, spleen, & bone marrow – Iron recycled back into hemoglobin production Fig 13.4 13-14 RBC Antigens & Blood Typing • Antigens present on RBC surface specify blood type • Major antigen group is ABO system – – – – Type A blood has only A antigens Type B has only B antigens Type AB has both A & B antigens Type O has neither A or B antigens 13-15 Transfusion Reactions • People with Type A blood make antibodies to Type B RBCs, but not to Type A • Type B blood has antibodies to Type A RBCs but not to Type B • Type AB blood doesn’t have antibodies to A or B • Type O has antibodies to both Type A & B • If different blood types are mixed, antibodies will cause mixture to agglutinate Fig 13.5 13-16 Transfusion Reactions continued • If blood types don't match, recipient’s antibodies agglutinate donor’s RBCs • Type O is “universal donor” because lacks A & B antigens • Insert fig. 13.6 – Recipient’s antibodies won’t agglutinate donor’s Type O RBCs • Type AB is “universal recipient” because doesn’t make anti-A or anti-B antibodies – Won’t agglutinate donor’s RBCs Fig 13.6 13-17 Rh Factor • Is another type of antigen found on RBCs • Rh+ has Rho(D) antigens; Rh- does not • Can cause problems when Rh- mother has Rh+ babies – At birth, mother may be exposed to Rh+ blood of fetus – In later pregnancies mom may produce Rh antibodies • In Erythroblastosis fetalis, this happens & antibodies cross placenta causing hemolysis of fetal RBCs 13-18 Hemostasis • Is cessation of bleeding • Promoted by reactions initiated by vessel injury: – Vasoconstriction restricts blood flow to area – Platelet plug forms • Plug & surroundings are infiltrated by web of fibrin, forming clot 13-19 Role of Platelets • Platelets don't stick to intact endothelium because of presence of prostacyclin (PGI2--a prostaglandin) & NO – Keep clots from forming & are vasodilators Fig 13.7a 13-20 Structure of Heart • Heart has 4 chambers – 2 atria receive blood from venous system – 2 ventricles pump blood to arteries – 2 sides of heart are 2 pumps separated by muscular septum Fig 13.10 13-29 Structure of Heart continued • Between atria & ventricles is layer of dense connective tissue called fibrous skeleton – Which structurally & functionally separates the two • Myocardial cells of atria attach to top of fibrous skeleton & form 1 unit (or myocardium) • Cells from ventricles attach to bottom & form another unit – Fibrous skeleton also forms rings, the annuli fibrosi, to hold heart valves 13-30 Pulmonary & Systemic Circulations • Blood coming from tissues enters superior & inferior vena cavae which empties into right atrium, then goes to right ventricle which pumps it through pulmonary arteries to lungs Fig 13.10 13-31 Pulmonary & Systemic Circulations continued • Oygenated blood from lungs passes thru pulmonary veins to left atrium, then to left ventricle which pumps it through aorta to body Fig 13.10 13-32 Pulmonary & Systemic Circulations continued • Pulmonary circulation is path of blood from right ventricle through lungs & back to heart • Systemic circulation is path of blood from left ventricle to body & back to heart • Rate of flow through systemic circulation = flow rate thru pulmonary circuit Fig 13.10 13-33 Pulmonary & Systemic Circulations continued • Resistance in systemic circuit > pulmonary – Amount of work done by left ventricle pumping to systemic is 5-7X greater • Causing left ventricle to be more muscular (3-4X thicker) Fig 13.11 13-34 Heart Valves 13-35 Atrioventricular Valves • Blood flows from atria into ventricles thru 1-way atrioventricular (AV) valves – Between right atrium & ventricular is tricuspid valve – Between left atrium & ventricular is bicuspid or mitral valve Fig 13.11 13-36 Atrioventricular Valves continued • Opening & closing of valves results from pressure differences – High pressure of ventricular contraction is prevented from everting AV valves by contraction of papillary muscles which are connected to AVs by chorda tendinea 13-37 Semilunar Valves • During ventricular contraction blood is pumped through aortic & pulmonary semilunar valves – Close during relaxation Fig 13.11 13-38 Structure of Blood Vessels 13-65 Structure of Blood Vessels • Innermost layer of all vessels is the endothelium • Capillaries are made of only endothelial cells • Arteries & veins have 3 layers called tunica externa, media, & interna – Externa is connective tissue – Media is mostly smooth muscle – Interna is made of endothelium, basement membrane, & elastin • Although have same basic elements, arteries & veins are quite different 13-66 Arteries • Large arteries are muscular & elastic – Contain lots of elastin – Expand during systole & recoil during diastole • Helps maintain smooth blood flow during diastole 13-67 Arteries • Small arteries & arterioles are muscular – Provide most resistance in circulatory system – Arterioles cause greatest pressure drop – Mostly connect to capillary beds • Some connect directly to veins to form arteriovenous anastomoses Fig 13.27 13-68 Capillaries • Provide extensive surface area for exchange • Blood flow through a capillary bed is determined by state of precapillary spincters of arteriole supplying it Fig 13.27 13-69 Types of Capillaries • In continuous capillaries, endothelial cells are tightly joined together – Have narrow intercellular channels that permit exchange of molecules smaller than proteins – Present in muscle, lungs, adipose tissue • Fenestrated capillaries have wide intercellular pores – Very permeable – Present in kidneys, endocrine glands, intestines. • Discontinuous capillaries have large gaps in endothelium • Are large & leaky • Present in liver, spleen, bone marrow. 13-70 Veins • Contain majority of blood in circulatory system • Very compliant (expand readily) • Contain very low pressure (about 2mm Hg) – Insufficient to return blood to heart 13-71 Veins Fig 13.30 • Blood is moved toward heart by contraction of surrounding skeletal muscles (skeletal muscle pump) – & pressure drops in chest during breathing – 1-way venous valves ensure blood moves only toward heart 13-72 Heart Disease 13-73 Atherosclerosis • Is most common form of arteriosclerosis (hardening of arteries) Fig 13.32 – Accounts for 50% of deaths in US • Localized plaques (atheromas) reduce flow in an artery – & act as sites for thrombus (blood clots) 13-74 Atherosclerosis • Plaques begin at sites of damage to endothelium – E.g. from hypertension, smoking, high cholesterol, or diabetes Fig 13.32b 13-75 Lymphatic System 13-86 Lymphatic System • Has 3 basic functions: – Transports interstitial fluid (lymph) back to blood – Transports absorbed fat from small intestine to blood – Helps provide immunological defenses against pathogens 13-87 Lymphatic System continued • Lymphatic capillaries are closed-end tubes that form vast networks in intercellular spaces – Very porous, absorb proteins, microorganisms, fat Fig 13.37 13-88 Lymphatic System continued • Lymph is carried from lymph capillaries to lymph ducts to lymph nodes Fig 13.38 13-89 Lymphatic System continued • Lymph nodes filter lymph before returning it to veins via thoracic duct or right lymphatic duct • Nodes make lymphocytes & contain phagocytic cells that remove pathogens • Lymphocytes also made in tonsils, spleen, thymus Fig 13.39 13-90 Mucosal Associated Lymphoid Tissues • • • • Tonsils Peyers patches Appendix w/ GALT Others!