Anatomy II Exam II The Cardiovascular System The function of the cardiovascular system is to delver oxygen and nutrients and to remove carbon dioxide and other waste products Transport of substances such as o Oxygen and nutrients to cells o Wastes from cells to liver and kidneys o Hormones immune cells clotting proteins to specific target cells A closed system of the heart and blood vessels o The heart pumps blood o Blood vessels allow blood to circulate to all parts of the body Blood is used for delivery Overview of the Cardiovascular System The Heart o Located in thoracic cavity o Diaphragm separates abdominal cavity from thoracic cavity o Size of fist o Weighs approximately 250 350 grams o Valves present for unidirectional blood flow o Four chambers 2 atria and 2 ventricles o Blood vessels o Blood Properties of Cardiac Muscle Intercalated Disks o Gap junctions so heart contracts as a unit o Desmosomes resist stress Aerobic muscle No cell division after infancy growth by hypertrophy 99 contractile cells 1 Autorhythmic cells The Heart s Covering The Pericardium Pericardium is a double walled membranous sac surrounding heart o Serous fluid fills the space between the layers of pericardium o Lubricates heart decreasing friction o Pericarditis inflammation of pericardium The Heart 4 Chambers Right and left side act as separate pumps Septa separates chambers Interventricular septum o Separates the two ventricles Interatrial septum o Separates the two atria Four chambers o Atria are retrieving chambers left and right o Ventricles are discharging chambers left and right The Heart Valves Allow blood to flow in only one direction to prevent backflow Four valves o Atrioventricular AV valves are between the atria and ventricles Bicuspid mitral valve left side of heart Tricuspid valve right side of heart o Semilunar valves are between ventricle and artery Pulmonary semilunar valve Aortic semilunar valve AV valves Semilunar valves through the heart o Anchored in place by chordae tendineae heart strings o Open during heart relaxation and closed during ventricular contraction o Closed during heart relaxation but open during ventricular contraction These valves operate opposite of one another to force a one way path of blood Valves and Unidirectional Blood Flow Pressure within chambers of heart vary with heartbeat cycle Pressure difference drives blood flow high pressure to low pressure Normal direction of flow o Veins to atria o Atria to ventricles o Ventricles to arteries Valves prevent backward flow of blood All valves open passively based on pressure gradient Blood Vessels Vasculature Heart arteries arterioles capillaries venules veins Arteries are relatively large branching vessels that conduct blood away from the heart Arterioles are small branching vessels with high resistance Capillaries are the site of exchange between blood and tissue Venules are small converging vessels Veins are relatively large converging vessels that conduct blood to the heart Closed system Pressure drives blood flow Series Flow Through The Cardiovascular System Parallel flow within the systemic or pulmonary circuit o Pulmonary circuit supplied by right heart blood vessels from heart to lungs and lungs to heart o Systemic circuit supplied by left heart blood vessels from heart to systemic tissues and tissues to heart Left ventricle aorta systemic circuit venae cavae right atrium right ventricle pulmonary artery pulmonary circuit pulmonary veins left atrium left ventricle Oxygenation of Blood Exchange between blood and tissue takes place in capillaries Pulmonary capillaries Systemic capillaries o Blood entering lungs deoxygenated blood o Oxygen diffuses from tissue to blood o Blood leaving lungs oxygenated blood o Blood entering tissues oxygenated blood o Oxygen diffuses from blood to tissue o Blood leaving tissues deoxygenated blood Coronary Circulation Intrinsic conduction system nodal system heart muscle cells contract without nerve impulse in a regular continuous way Blood in the heart chambers does not nourish the myocardium The heart has its own nourishing circulatory system o Coronary arteries branch from the aorta to supply the heart muscles with o Cardiac veins drain the myocardium of blood o Coronary sinus a large vein on the posterior of the heart receives blood oxygenated blood from cardiac veins o Blood empties into the right atrium via the coronary sinus o Bypass surgery Differences Between Blood Vessels Walls of arteries are the thickets Lumens of veins are larger Larger veins have valves to prevent backflow Skeletal muscle squeeze blood in veins toward the heart Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue Have to be able to stretch Blood Vessels Microscopic Anatomy Three layers o Tunica intima endothelium o Tunica media Smooth muscle Controlled by sympathetic nervous system Radius can be altered May be used to control blood flow to individual capillary beds Used to regulate mean arterial pressure o Tunica externa is mostly fibrous connective tissue Rapid transport pathway large diameter little resistance Walls contain elastic and fibrous tissue under high pressure Smooth muscle regulates radius Major arteries o Aorta leaves left ventricle o Pulmonary arteries leave right ventricle Arteries Capillaries Site of exchange between blood and tissue Substances exchanged due to concentration gradients Oxygen and nutrients leave the blood Carbon dioxide and other wastes leave the cells Walls are 1 cell layer small diffusion barrier Most cells within 1 mm of a capillary Pores between endothelial cells protein free plasma moves through pores 10 40 billion per body total surface area 600 m2 Capillary Exchange Mechanisms Direct diffusion across plasma membranes Endocytosis or exocytosis Some capillaries have gaps intercellular clefts plasma membrane not joined by tight junctions Fenestrations pores of some capillaries Penicillin can not pass blood brain barrier Fluid Movements at Capillary Beds Blood pressure forces fluid and solutes out of capillaries Osmotic pressure draws fluid into capillaries Blood pressure is higher than osmotic pressure at the arterial end of the capillary Blood pressure is lower than osmotic pressure at the venous end of the capillary bed bed More fluid leaves not much coming in edema Precapillary Sphincters Rings of smooth muscle that surrounds capillaries on the arteriole end o Contract relax in response to local factors only o
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