Lecture 6 (Cardiovascular I) PDF

Cardiovascular I: Overview, Anatomy of the Heart ANSC 3080 G. Bedecarrats Learning Objectives ¾ Describe the structure of the heart ¾ Describe the structure and functions of the pulmonary and systemic circulations ¾ Describe the cardiac...

Cardiovascular I: Overview, Anatomy of the Heart ANSC 3080 G. Bedecarrats Learning Objectives ¾ Describe the structure of the heart ¾ Describe the structure and functions of the pulmonary and systemic circulations ¾ Describe the cardiac cycle Overview of the C.V.S. ¾Heart ¾4 chambers and 4 sets of valves form 2 sets of pumps ¾Atria (2) ¾Ventricles (2) ¾AV valves: tricuspid, bicuspid ¾Semi-lunar valves: aortic and pulmonary ¾Pulmonary circulatory system ¾Arteries to, and veins from the lungs ¾Systemic circulatory system ¾Arteries to, and veins from the rest of the body ¾ Heart separated into 2 parts = prevents mixing of oxygenated and un-oxygenated blood 1  Major Functions of the CVS ¾Transport O2/CO2 from and to the lungs and tissues ¾Transport of nutrients: ¾From intestine to tissues ¾From and to the liver (factory) and fat (storage) ¾Transport waste: from production to excretion sites ¾Transport heat: from inside to the skin ¾Transport hormones: endocrine glands to target cells ¾Carrying immune cells ¾Stabilize internal environment: buffer (pH, ions etc…) Anatomy of the Heart ¾ Pericardium = 2 layers of connective tissue with a cavity ¾ Visceral layer, attached to the heart wall ¾ Reinforced parietal layer ¾ Prevents over-sizing (overstretching) of the heart ¾ Cavity filled with fluid = allows some movement 2 ¾Two atria ¾Mainly serve as reservoirs ¾Help transfer blood to the ventricles ¾Two ventricles ¾Propel blood into systemic and pulmonary circulation ¾The heart wall ¾Muscle tissue = myocradium ¾Heart halves separated by a muscular septum ¾Endocardium = epithelium covering the inner surface (equivalent to endothelium of blood vessels) 3  ¾The heart valves ¾Made of fibrous connective tissue attached to a fibrous ring ¾Allow blood to flow only 1 direction ¾Atrio-ventricular (AV) valves: ¾Bicuspid (mitral) on the left ¾Tricuspid on the right ¾Free end of AV valves attached to papillary muscle in ventricle (prevents inversion, limits movement) ¾Semilunar valves ¾Aortic: between left ventricle and aorta ¾Pulmonary: between right ventricle and pulmonary artery AV Valve (Tricuspid) Chordae Tendineae Papillary Muscle a b c d ¾ 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 4  Great Vessels ¾Arteries ¾Convey blood from the heart to tissues & organs ¾Pulmonary arteries ¾Leave the right ventricle to bring deoxygenated blood to the lungs ¾Aorta: ¾Leaves the left ventricle to bring oxygenated blood to the rest of the body ¾Veins ¾Convey blood from the tissues & organs to the heart ¾Vena cava (2: cranial or superior and caudal or inferior) ¾Bring deoxygenated blood to the right atrium ¾Pulmonary vein ¾Brings oxygenated blood to the left atrium Blood Vessels ¾ Arteries branch off the aorta and pulmonary arteries ¾ Receive tremendous pressure from ventricle contractions, need to be elastic ¾ Conducting vessels for blood ¾ Small arteries ¾ Deliver blood locally to arterioles and capillaries in tissues ¾ Control the pressure via tone of vessel’s smooth muscle ¾ Capillaries ¾ Site of gas exchange, nutrient etc… ¾ Venules: collect blood from capillaries ¾ Veins: ¾ Receive blood from venules and return it to the heart ¾ Change in tone will alter “venous return” Systemic/Pulmonary Systems ¾Both have arteries and veins ¾Pulmonary = heart/lungs loop to oxygenate blood ¾Relatively low pressure, low resistance, highly distensible ¾Systemic = distribution of oxygenated blood and nutrient throughout the body ¾High pressure, high resistance ¾Work performed by the left ventricle is 5-7 fold greater than right ventricle = wall much thicker 5  Cardiac output: Blood pumped by each half of the heart per minute Right heart Left heart Cardiac Cycle ¾Repeating pattern of contraction and relaxation of the heart ¾Systole = Phase of contraction ¾Diastole = Phase of relaxation/filling ¾Two step pumping ¾Both atria contract simultaneously = push blood in ventricles ¾Right and left ventricles contract 0.1 to 0.2 sec later 6 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) 7