CARDIOVASCULAR SYSTEM Replacing hearts - nova CARDIOVASCULAR SYSTEM

Cardiovascular System Functions The cardiovascular system allows exchange of oxygen and carbon dioxide between blood and tissues Accomplished by three components: Heart – pump blood Vessels – transport network; arteries, veins and capillaries Blood – transports dissolved gases, nutrients, hormones and metabolic wastes Our body cells rely on the surrounding interstitial fluid for oxygen, nutrients and waste disposal. Conditions in the interstitial fluid are kept stable through continuous exchange between the peripheral tissues and circulating blood.

Organization of Cardiovascular System A closed system with two circuits Systemic Circuit – oxygenated blood leaves the heart through the aorta and returns to the heart through systemic veins Pulmonary Circuit– deoxygenated blood leaves the heart through pulmonary arteries and returns to the heart through pulmonary veins

The Heart…size, shape and location Muscular organ composed of cardiac muscle About the size of a closed fist Weighs less than a pound Located within the thoracic cavity Flanked on either side by the lungs At rest, the average adult heartbeat is 72 beats per minutes. This is equal to 100,000 beats per day. 2 ounces of blood is pumped each minute which means 75 gallons of blood are pumped in one hour.

The heart…coverings and wall Pericardium = double walled sac around the heart Protects the heart and anchors it to surrounding structures Produces a lubricating fluid to create a frictionless environment Pericarditis = inflammation of the pericardium

The heart…coverings and wall The wall of the heart is composed of three layers: Epicardium = continuous with the pericardium Myocardium = thick bundles of cardiac muscle; the contractile part of the heart Endocardium = think sheet of endothelium that lines the heart chambers

The heart…coverings and wall

Anatomy of the heart 4 chambers Upper chambers = atria = receiving chambers Lower chambers = ventricles = pumping chambers Left ventricle forms the apex or point of the heart Interventricular septum divides ventricles

Chambers – Anterior View Left atrium Right atrium Right Ventricle Left Ventricle

Chambers – Posterior View Left atrium Right atrium Right Ventricle Left Ventricle

Chambers – Internal View Left atrium Right atrium Left Ventricle Right Ventricle

Right Atrium Tricuspid Anatomy of the heart Heart Valves permit flow of blood in one direction 1. AV valves divide atria and ventricles; prevent backflow of blood into atria when ventricles contract Bicuspid valve (mitral valve) – between left atria and left ventricle Tricupsid valve between right atria and right ventricle Chordae Tendinae = tiny white cords that anchor the valves to the walls of the ventricle When the heart is relaxed and the atria are filling, the AV flap hang open into the ventricle. As the ventricles contract, the pressure within the ventricle increases which forces the AV flaps upward. The chordae tendinae at this point are keeping the flaps from blowing upward into the atria. LAB RAT… Left Atrium Bicuspid Right Atrium Tricuspid

AV Valves

Anatomy of the heart Heart Valves permit flow of blood in one direction 2. Semilunar valves guard the large vessels leaving the ventricles; prevents arterial blood from falling back into the ventricles Pulmonary semilunar valve Aortic semilunar valve

Semilunar Valves

Each set of valves operates at a different time in a contraction cycle Each set of valves operates at a different time in a contraction cycle. The AV valves are open during relaxation and are forced closed when the ventricles contract. The semilunar valves are closed during relaxation and forced open during contractions. The valves open and close in response to pressure changes

Anatomy of the heart Great Vessels of the Heart Superior and inferior vena cava – take deoxygenated blood from the body to the right atrium Pulmonary trunk gives rise to Pulmonary arteries (left and right) – take deoxygenated blood from right ventricle to lungs for oxygen Pulmonary veins (left and right) – takes oxygenated blood from lungs to left atrium Aorta – takes blood away from left ventricle to rest of body

Anatomy of the heart Cardiac Circulation Coronary arteries branch from the base of the aorta and encircle the heart at the junction between the atria and ventricles Compressed when ventricles are contracting and fill when the ventricles are relaxed Cardiac veins drain the myocardium into the right atrium Although the heart is bathed in blood, The blood that is contained within the heart isn’t given enough time to supply the myocardium with nutrients so the heart has its own blood supply called the cardiac arteries.

Vessels – Anterior View aorta L. Pulmonary artery Superior vena cava Pulmonary trunk R. Pulmonary artery R. Pulmonary veins L. Pulmonary veins Coronary vessels Inferior vena cava

Vessels – posterior view Superior vena cava aorta R. Pulmonary artery L. Pulmonary artery R. Pulmonary veins L. Pulmonary veins Inferior vena cava Coronary vessels

When the heart beats The Right side of the heart Deoxygenated blood flows into heart from vena cava Right atrium Tricuspid valve Right ventricle Pulmonary semilunar valve Pulmonary artery Lungs (to pick up oxygen)

What’s behind a heartbeat The Left side of the heart Oxygenated blood flows into heart from lungs via pulmonary veins Left atrium Bicuspid valve (aka mitral valve) Left ventricle Aortic semilunar valve Aorta Body (to deliver oxygen)

Control of Heart Contraction General info about cardiac muscle Cardiac muscle cells contract spontaneously and independently, even if all nervous connections are cut Muscle cells in different areas of the heart have different rythms Atria cells contract at a faster rate than ventricular cells An intrinsic control system regulates activity

Intrinsic Control System Intrinsic conduction system Sinoatrial node (SA node) Atrioventricular node (AV node) Bundle of His Purkinje Fibers

Sinoatrial Node (SA node) The pacemaker of the heart Located in right atrium SA node sends out electrical impulse Impulse spreads over atria, making them contract Impulse travels to AV node

Atrioventricular node (AV node) Conducting cell group between atria and ventricle Carries impulse to bundle of His

Bundle of His Conducting fibers in septum (divider between left and right sides of the heart Divides into right and left branches to a network of b ranches in ventricles (Purkinje Fibers)

Purkinje Fibers Impulse shoots along Purkinje fibers causing ventricles to contract

Electrocardiogram (EKG or ECG) Device used to record the electrical activity of the heart Systole = contraction phase Diastole = relaxation phase Baseline of EKG is flatline P = atrial contraction QRS = ventricular contraction T = ventricular relaxation