Anatomy of the Heart Heart is approximately the

Anatomy of the Heart

�Heart is approximately the size of your fist and weighs less than a pound. �Located within bony thorax (ribs) and is flanked on each side by lungs �Apex points toward your left hip and rests on your diaphragm

Wall of the Heart �The heart is enclosed by double sac of serous membrane called pericardium �The heart walls are composed of 3 layers: • Epicardium – visceral tissue that tightly hugs the heart • Myocardium – thick bundles of cardiac muscle; this is the layer that contracts • Endocardium – thin, glistening sheet of endothelium that lines the heart chambers; continuous with linings of blood vessels

Coverings/wall of heart

Chambers of the Heart � The heart has four hollow chambers: • Two atria • Two ventricles Each chamber is lined with endocardium to help blood flow smoothly through heart Atria lie superior to ventricles and receive blood under low pressure from veins of body. Atria are separated by interatrial septum. Ventricles lie inferior to atria and receive blood from atria. Ventricles contract to force blood into circulation. Ventricles are separated by interventricular septum

Valves of the Heart �The heart has 4 valves which allow blood to flow in only one direction

• AV valves (atrioventricular) are located between each atrial and ventricular chambers on each side. �Bicuspid (mitral) valve – consists of two cusps of endocardium; located between left atrium and left ventricle �Tricuspid valve – consists of three cusps; located between right atrium and right ventricle �Chordae tendinae (“heart strings”) – tiny white chords which anchor wall of cusps of AV valves to ventricles. Anchor cusps of AV valves in a closed position when ventricles contract. This prevents blood from leaking back into atria.

�Semilunar Valves – Guard the bases of the two large arteries leaving the ventricles. • Pulmonary Semilunar Valve- guards the opening of the pulmonary trunk • Aortic Seminlunar Valve – guards opening of aorta Each SL valve has 3 cusps which fit tightly together when closed and are forced open and flattened against atrial walls when ventricles contract to force blood out of heart

Valves

Mitral Valve Prolapse

Circulation �The right side of heart functions as pulmonary circuit pump. It receives oxygen-poor blood from body through the Superior and Inferior Venae Cavae and pumps this blood out through the Pulmonary Trunk

Pulmonary Circulation �The pulmonary trunk splits into right and left pulmonary arteries, which carry blood to lungs where it picks up Oxygen and unloads Carbon Dioxide. �Oxygen-rich blood drains returns from lungs to left side of heart through 4 pulmonary veins, �This path from right side of heart to lungs and back to left side of heart = Pulmonary Circulation

Systemic Circulation �Blood returning to left side of heart is deposited into the left atrium and then flows into the left ventricle. The left ventricle forces blood through the aorta to the systemic arties to supply oxygen to all body tissues and then back to right atrium �This path from left side of heart through body tissues and back to right side of heart = Systemic Circulation

Aorta �The largest artery of the body �Size of garden hose (diameter) �Springs from left ventricle (ascending aorta), arches to the left (aortic arch), and then plunges downward (descending aorta)

The Path of Circulation

The Path of Circulation through the Heart

�Oxygen-poor blood returns from body through the inferior (5) and superior (1) cavae and empties into the right atrium(2). Blood then flows through the tricuspid valve into the right ventricle (4). Right ventricle contracts forcing blood against the pulmonary SL valve forcing it open. Blood exits the heart and enters the lungs via right and left pulomonary arteries (8).

�Blood picks up Oxygen and deposits Carbon Dioxide in capillary beds of lungs (10). Oxygen-rich blood now returns to left atrium (7) via right and left pulmonary veins (3). As left atrium fills with blood, pressure is exerted on mitral valve (bicuspid) and it is forced open allowing blood to fill left ventricle (6). Left ventricle contracts forcing aortic SL valve open and allowing blood to leave heart through aorta (9).

Double Pump �Both sides of the heart are pumping at the same time.

�In a healthy heart, the both atria contract simultaneously. At they begin to relax, contraction of the ventricles begins. �Systole = contraction of ventricles �Diastole = relaxation of ventricles

Cardiac circulation �Blood supply that nourishes the heart is accomplished by right and left coronary arteries which branch from base of aorta and encircle the heart. �Coronary arteries are compressed when ventricles are contracting and fill with blood when heart is relaxed �Myocardium is drained by several cardiac veins which empty into enlarge vessel on backside of heart called coronary sinus, which in turn empties into right atrium.

Coronary arteries

Coronary sinus