Cardiovascular system and blood vessels I Basic Anatomy of the Heart a Systemic circuit left side of heart supplies blood to all organs of body b Pulmonary circuit right side of heart supplies blood to lungs c Pericardium cavity function allows heart to beat w o friction heart can expand but not excessively secretes serous fluid to help d Myocardium thick muscular middle layer i Fibrous skeleton network of collagenous and elastic fibers ii Provides structural support and attachment for cardiac muscle iii Electrical nonconductor impt in coordinating contractions e Blood flow through the heart superior inferior vena cava right atrium right AV valve right ventricle pulmonary valve pulmonary arteries lungs pulmonary veins left atrium left AV valve left ventricle aortic valve aorta body tissues organs f Right and left atria superior posterior chambers that receive blood returning to heart i Thinner more flaccid walls than ventricles ii Each has auricle extension that can take in more blood if needed g Right and left ventricles inferior chambers pump blood into arteries i Left is much thicker than right b c it pumps blood to entire body rather than just lungs ii Left experiences far more resistance than right h Septums interventricular interatrial separate the right and left chambers i Atrioventricular AV valves control flow b w atria and ventricles i Right has 3 cusps tricuspid left has 2 cusps bicuspid ii Chordae tendinae that attach AV valves to papillary muscles on the floor of ventricles 1 Papillary muscles contract during contraction prevent AV valves from bulging back into the atria 2 Contracting papillary muscles pull on tendinous cords which attach to valves 3 Papillary muscles do not actually open close the valves j Semilunar valves control flow into great arteries i Pulmonary from right ventricle to pulmonary trunk ii Aortic from left ventricle to aorta k Valves ensure blood flow is entirely in one direction l Valve mechanics ventricles relax i Vent pressure drops ii Semilunar valves close iii AV valves open iv Blood moves from atria to ventricles m Valve mechanics ventricles contract i Vent pressure rises ii AV valves pushed closed by blood in ventricles iii Semilunar valves open iv Blood flows into aorta pulmonary trunk II Basic Anatomy of the Blood Vessels a Tunica Interna innermost layer in contact w blood i Simple squamous endothelium over basement membrane of loose connective tissue ii Endothelium is selectively permeable barrier secretes chemicals to dilate constrict vessel iii Repels blood cells and platelets platelets only stick if there is damage to the vessel iv Very thin so it is a nourishing layer v Basal lamina protein carb layer of basement membrane helps anchor endothelium b Tunica Media middle thickest layer i Smooth muscle collagen and elastic tissue ii Smooth muscle allows for vasomotion diameter change in vessel iii Strengthens wall prevents rupture from BP changes iv Amounts of smooth muscle elastic vary in different types of vessels c Arteries i Carry blood away from the heart ii Strong and can resist surges in BP iii Round shape while empty due to muscularity iv Conducting elastic arteries largest 1 Pulmonary trunk aorta common carotid subclavian common iliac 2 Tunica media has many layers of perforated elastic tissue alternating with layers of smooth muscle collagen and elastic tissue 3 Expand during ventricular contraction and recoil during ventricular relaxation a Recoil allows for BP to stay relatively constant stable b No other arteries can expand relax like this c BP becomes wave function without recoil it would peak crash to zero v Small arteries 1 Vary in number and location around body 2 Arterioles are smallest control amount of blood to various organs In direct contact w capillary beds a b Mostly smooth muscle very little elastic tissue 3 Metarterioles connect arterioles to capillaries a No continuous tunica media b Muscle cells placed short distances apart each circling entrance to one capillary known as the precapillary sphincter vi Arterial sense organs detect BP and chemistry changes located in major arteries above heart 1 Baroreceptors a Aortic arch and carotid sinus in wall of internal carotid artery Internal carotid goes to brain most impt sensor is there i ii Check on BP before it goes to brain b Monitors BP and alerts cardiac and vasomotor centers of medulla c If BP increases HR drops and vessels dilate and vice versa 2 Chemoreceptors a Carotid and aortic bodies oval bodies near common carotids in aortic arch b Monitor changes in blood chemistry c Adjust breathing rate to stabilize blood pH CO2 and O2 d Transmit info to respiratory center of brainstem d Capillaries i Connect smallest arteries to smallest veins ii Exchange occurs thru these vessels 1 So small that RBCs have to straighten out to squeeze thru some 2 Almost every cell in the body is near a capillary iii Composed only of endothelium w basal lamina and basement membrane iv Continuous capillaries 1 Occur in most tissues 2 Endothelial cells have tight junctions forms continuous tube w intercellular clefts 3 Allow small molecules like glucose to pass thru cleft 4 In brain much tighter together no clefts forms blood brain barrier v Fenestrated capillaries 1 Many holes called filtration pores fenestrations in endothelial cells 2 Rapid passage of small molecules still blocks larger molecules proteins 3 4 Basal lamina helps stop passage of larger molecules Important in organs that engage in rapid absorption filtration vi Sinusoids discontinuous Irregular blood filled spaces in liver spleen and bone marrow 1 2 Allow blood cells to pass some blood cells too 3 4 In liver proteins can pass no blood cells b c liver makes proteins In bone marrow new blood cells can pass to enter circulation vii Organized into capillary beds about 100 caps supplied by a single metarteriole viii Metarteriole continues thru bed as thoroughfare channel straight to venule no sphincters ix Precapillary sphincters control what capillaries are perfused with blood x Capillaries empty into distal end of thoroughfare channel or directly into venule xi About of body s caps are shut down at any given time simply not enough blood xii Blood flow depends on metabolic activity of that tissue e g skeletal muscle at rest gets little e Veins i Carry blood back to heart ii Expand easily and have high capacitance iii Thinner walls less muscular and elastic tissue iv Tend to flatten out when empty v Very low BP around