How+the+heart+works


 * How the heart works**

· Electrical system regulates contractions of heart walls o Contraction pump blood into circulatory system · Carries oxygen and nutrients to body and carries carbon dioxide to lungs to be expelled from body o When diseased or injured, body organs will not receive enough blood to work normally · Right side of heart o Superior and inferior vena cavae largest veins o Vena cavae carry oxygen-poor blood to right atrium of heart § Superior carries blood from upper parts of the body including head, chest, arms, neck § Inferior carries blood from lower parts o Blood from right atrium to right ventricle o Right ventricle pumps blood through pulmonary arteries to lungs then through capillaries to pick up oxygen § Right pulmonary veins pump blood to right lung § Left pulmonary veins pump blood to left lung · Left side of heart o Oxygen rich blood from lungs pass through pulmonary veins o Enters left atrium and pumped to left ventricle o Left ventricle pumps blood through aorta to rest of body § Also pumps blood to coronary arteries · Located on hearts surface at beginning of aorta · Septum o Internal tissue that divides left and right sides of your heart · Heart valves o Four valves § Aortic valve § Tricuspid valve § Pulmonary valve § Mitral valve · Blood flow o Blood must flow in only one direction § Flow kept in check by valves · Inlet valve from atria · Outlet valve leading to arteries · Healthy valves open and close in coordination with pumping of atria and ventricles · Valves have set of flaps called leaflets or cusps to seal or open valves · Heartbeat o Inlet valve help move blood between atrium and ventricle § Tricuspid valve between right atrium and ventricle § Mitral valve between left atrium and ventricle o Outlet valve § Right ventricle uses pulmonary valve to move blood into pulmonary arteries § Left ventricle uses aortic valve to move blood to aorta o Heartbeat has two parts § Diastole (relaxation) · ventricles and atria relax and fill with blood § Atrial and ventricular systole (contraction) · At end of diastole atria contract (atrial systole) and pump blood into ventricles · Atria relax and ventricles contract (ventricular systole) and pump blood out of heart · Pumping action o Oxygen-poor blood from vena cavae fills right atrium o Atrium contracts (atrial systole) o Tricuspid valve opens shortly then shuts § Allows blood to enter right ventricle without flowing back into right atrium o Right ventricle fills with blood and contracts (ventricular systole) o Pulmonary valve opens and closes quickly § Allows blood to enter pulmonary arteries without flowing back into right ventricle § Important because right ventricle refills with more blood through tricuspid valve o Blood flows through pulmonary arteries to lungs to get oxygen o Oxygen-rich blood returns from lungs to left atrium through pulmonary veins o Left atrium fills with blood and contracts (atrial systole) o Mitral valve opens and closes quickly § Allows blood to pass from left atrium to left ventricle without backward flow o Left ventricle fills with blood and contracts (ventricular systole) o Aortic valve opens and closes quickly § allowing blood to flow to aorta and prevents flood to flow backwards · electrical system that control events that cause heart to pump called cardiac conduction system o electrocardiogram (EKG)- graphical picture of electrical activity o made of three main parts § sinoatrial (SA) node, located in right atrium § atrioventricular (AV) node located on interatrial septum close to the tricuspid valve § His-Purkinje system located along walls of heart’s ventricles o Each beat in heart is started by electrical signal from within heart muscle § Healthy heart begins with signal from SA node · SA node called pacemaker · Pulse or heartrate is the number of signals the SA node produces per minute § Signal generated when two vena cavae fill right atrium with blood § Signal spreads across the cells of right and left atria and causes atria to contract § Signal arrives at the AV node and slows down a little to allow blood to fill the left and right ventricles § Signal released and moves along bundle of His § Signal divides left and right bundle branches through purkinje fibers that connect directly to cells in walls of left and right ventricle § Signal spreads across cells of ventricle and both ventricles contract · Left ventricle contracts right before the right ventricle o Pushes blood through the pulmonary valve (right ventricle) to lungs and through aortic valve (left ventricle) to body § []