Cardiovascular I: Overview, Anatomy of the Heart Lecture 6 PDF

Cardiovascular I: Overview, Anatomy of the Heart ANSC 3080 G. Bedecarrats  Learning Objectives  Describe the structure of the heart  Describe the structure and functions of the pulmonary and systemic circulations  Describe the cardiac cycle  Overview of the C.V.S. ...

Cardiovascular I: Overview, Anatomy of the Heart ANSC 3080 G. Bedecarrats  Learning Objectives  Describe the structure of the heart  Describe the structure and functions of the pulmonary and systemic circulations  Describe the cardiac cycle  Overview of the C.V.S.  Heart 4 chambers and 4 sets of valves form 2 sets of pumps Atria (2) Ventricles (2) AV valves: tricuspid, bicuspid Semi-lunar valves: aortic and pulmonary  Pulmonary circulatory system Arteries to, and veins from the lungs  Systemic circulatory system Arteries to, and veins from the rest of the body  Heart separated into 2 parts = prevents mixing of oxygenated and un-oxygenated blood  Major Functions of the CVS  Transport O2/CO2 from and to the lungs and tissues  Transport of nutrients: From intestine to tissues From and to the liver (factory) and fat (storage)  Transport waste: from production to excretion sites  Transport heat: from inside to the skin  Transport hormones: endocrine glands to target cells  Carrying immune cells  Stabilize internal environment: buffer (pH, ions etc…)  Anatomy of the Heart  Pericardium = 2 layers of connective tissue with a cavity  Visceral layer, attached to the heart wall  Reinforced parietal layer  Prevents over-sizing (overstretching) of the heart  Cavity filled with fluid = allows some movement  Two atria Mainly serve as reservoirs Help transfer blood to the ventricles  Two ventricles Propel blood into systemic and pulmonary circulation  The heart wall Muscle tissue = myocradium Heart halves separated by a muscular septum  Endocardium = epithelium covering the inner surface (equivalent to endothelium of blood vessels)  The heart valves Made of fibrous connective tissue attached to a fibrous ring Allow blood to flow only 1 direction Atrio-ventricular (AV) valves: Bicuspid (mitral) on the left Tricuspid on the right Free end of AV valves attached to papillary muscle in ventricle (prevents inversion, limits movement) Semilunar valves Aortic: between left ventricle and aorta Pulmonary: between right ventricle and pulmonary artery AV Valve (Tricuspid) Chordae Tendineae Papillary Muscle a b c d  Opening and closing of valves = passive mechanism = dependent on blood pressure a) Ventricles relaxed = lower pressure = AV valves open b) Ventricles fool = higher pressure = AV valves closed c) Ventricles contract = pressure higher than arterial pressure  aortic and pulmonary valves open d) Ventricles emptied = pressure back down, all valves closed  Great Vessels  Arteries Convey blood from the heart to tissues & organs Pulmonary arteries Leave the right ventricle to bring deoxygenated blood to the lungs Aorta: Leaves the left ventricle to bring oxygenated blood to the rest of the body  Veins Convey blood from the tissues & organs to the heart Vena cava (2: cranial or superior and caudal or inferior) Bring deoxygenated blood to the right atrium Pulmonary vein Brings oxygenated blood to the left atrium  Blood Vessels  Arteries branch off the aorta and pulmonary arteries  Receive tremendous pressure from ventricle contractions, need to be elastic  Conducting vessels for blood  Small arteries  Deliver blood locally to arterioles and capillaries in tissues  Control the pressure via tone of vessel’s smooth muscle  Capillaries  Site of gas exchange, nutrient etc…  Venules: collect blood from capillaries  Veins:  Receive blood from venules and return it to the heart  Change in tone will alter “venous return”  Systemic/Pulmonary Systems  Both have arteries and veins  Pulmonary = heart/lungs loop to oxygenate blood Relatively low pressure, low resistance, highly distensible  Systemic = distribution of oxygenated blood and nutrient throughout the body High pressure, high resistance  Work performed by the left ventricle is 5-7 fold greater than right ventricle = wall much thicker  Cardiac output: Blood pumped by each half of the heart per minute Right heart Left heart  Cardiac Cycle  Repeating pattern of contraction and relaxation of the heart  Systole = Phase of contraction  Diastole = Phase of relaxation/filling  Two step pumping Both atria contract simultaneously = push blood in ventricles Right and left ventricles contract 0.1 to 0.2 sec later Physical Events of the Cardiac Cycle Left atrium Right atrium Right ventricle Left ventricle 1 5 Diastole 2 Isovolumic relaxation Atrial contraction Ejection 4 3 Isovolumic phase contraction (systole)