Unit 3- Cardiovascular System

CV system – function is to distribute oxygen and nutrients/remove wastes from the body’s tissues Made up of 2 parts: systemic [body] Left side and pulmonary [lungs] Right side Heart is the main organ of the system size of your clenched fist, 14 cm long by 9 cm wide located in the mediastinum (b/w the lungs laterally, spinal column and sternum, posteriorly and anteriorly respectively); apex points to the left and inferior (5th intercostal space, touching diaphragm), base is superior (beneath 2nd rib)  

Coverings – contained within a triple-layered membrane (pericardium) outer layer is fibrous pericardium (tough, dense) deep to that is the parietal pericardium covering the surface of the heart is the visceral pericardium. space b/w fibrous and visceral is pericardial cavity, filled with serous fluid - lubricates the heart. If pericardium becomes inflamed (pericarditis – can’t secrete fluid – membranes stick together- heart can’t move properly, severe chest pain, may require surgery)

The Heart Wall - 3 layers epicardium (aka visceral pericardium)– the outermost layer – usually has fat deposits along the surface myocardium – thick cardiac muscle – large blood supply, large nerve supply endocardium – elastic and collagen fibers

Heart Chambers – 4 chambers double pump 2 atria (“entrance room”) – superior - receive blood from veins then push it to the ventricles – not much myocardium, thinner walls than ventricles; only generate about 5 mm Hg pressure (each), smaller than ventricles, positioned superior to ventricles, pump blood to the ventricles. Contain ear-like projections – auricles – hollow, hold xs blood 2 ventricles - inferior to atria– thicker myocardium, pump blood out of the heart. Right vent – sends deoxyg, blood to lungs, generates about 25 mm Hg pressure; Left vent. – sends oxygenated blood to entire body, generates about 120 mm Hg pressure   interventricular, interatrial septum – walls that divide the heart into R & L halves

Valves [4]- regulate blood flow through the heart ATRIOVENTRICULAR [A-V] valves- control blood flow from atria to ventricle Right A-V valve- TRICUSPID [3 cusps] Left A-V valve- BICUSPID/MITRAL [2 cusps] SEMILUNAR valves- control blood flow out of the heart Pulmonary valve- allows blood to leave RIGHT Ventricle to go to the lungs Aortic valve- allows blood to leave LEFT Ventricle to go to aorta and to the body

Chordae tendonae- chords attached to the AV valves and anchor to walls of ventricle. Papillary muscle- chordae tendonae attached and pulled by papillary muscle [cardiac muscle]. Trabeculae carnae- muscular ridges on inside of heart, especially ventricles. Increase surface area.

Coronary Circulation-blood supply to the heart Rt and Lt coronary arteries branch off the Aorta and feed the Myocardium. Deox blood from Myocardium drain back to coronary sinus [back of heart by way of cardiac veins] into Rt Atrium

Pathologies of the Heart ISCHEMIA- partial blockage of coronary arteries Decrease in blood flow/ oxygen to heart muscle

ANGINA PECTORIS-pain radiates from neck, jaw, left arm and shoulder Diaphoresis [increased sweating] and dyspnea [difficulty breathing], nausea and vomiting Damage to cardiac cells MYOCARDIAL INFARCTION [MI- heart attack]- cardiac cells DIE Usually caused by a clot in the coronary arteries. Atherosclerosis – big factor in MI b/c it narrows the arteries. Cholesterol, smoking, obesity high risk factors.

Cardiac Cycle and Valves Cardiac Cycle-cycle of atrium and then ventricles contracting SYSTOLE= to contract DIASTOLE= to relax ATRIAL SYSTOLE: Blood flows into the atria – both contract at the same time increasing the pressure and forcing blood out through the AV valves into the ventricles Ventricles relax, increasing their volume and decreasing pressure, drawing blood in.

Increased pressure pushes the blood out through the SL valves. VENTRICULAR SYSTOLE: Then the ventricles contract, pushing the AV valves closed – chordae tendonae prevent backflow into atrium. Increased pressure pushes the blood out through the SL valves. DIASTOLE: When ventricles relax, pressure drops, pulling the SL valves closed. Their structure prevents them from opening inward.  

Heart Sounds Heart sounds – two sounds repeated – “lub- dub” valves opening and closing First sound – “lub” = ventricular contraction (systole) and AV valve closure Second sound – “dub” = ventricular relaxation (diastole) and SL valve closure *when ventricles relax, they expand and create a partial vacuum – forces SL valves to swing back and shut. Murmurs – incomplete closure of valves (valve prolapse) – may get backflow of blood into atria Can detect murmurs by listening: lub swish dub – AV valve damage lub dub swish – SL Valve damage