The Heart

The Heart The importance of the heart has been recognized for centuries It is a muscular pump that drives the blood through the blood vessels It is slightly bigger than your fist It is located between the lungs and a bit left of the midline of the body

Structures of the Heart Layers of the Heart Wall Endocardium A very thin smooth layer of cells that lines the interior of the heart. The valves of the heart are formed by reinforced folds of this material. Myocardium The muscle of the heart. It is the thickest layer and is responsible for the pumping of blood through the vessels.

Structures of the Heart Layers of the Heart Wall Epicardium The thin, outermost layer of the heart wall just on top of the myocardium. Pericardium It surrounds the entire heart. It keeps the heart contained in the chest cavity prevents the heart from overexpanding when blood volume increases.

Structures of the Heart Four Chambers On either side of the heart there are 2 chambers, one is a receiving chamber (atrium), and the other a pumping chamber (ventricle).

Structures of the Heart Right Atrium Has the thinnest walls out of all 4 chambers Receives blood low in oxygen returning from the body Right Ventricle Pumps blood received from the right atrium to the lungs Left Atrium Receives blood high in oxygen returning from the lungs Left Ventricle Has the thickest walls out of all 4 chambers Pumps oxygenated blood to all parts of the body

Structures of the Heart Four Valves There are one-way valves located at the entrance and exit of each ventricle. The entrance valves are called atrioventricular valves The exit valves are called semilunar valves Named because they look like a half-moon

Structures of the Heart Right Atrioventricular (AV) Valve Also known as the tricuspid valve, because it has 3 cusps, or flaps, that open and close When the valve is open, blood flows freely from the right atrium into the right ventricle. But when the ventricle contracts, the valve closes and no blood can return into the atrium.

Structures of the Heart Left Atrioventricular (AV) Valve Also known as the mitral valve, and is made up of 2 cusps, or flaps. Also called the Bicuspid Valve. The valve allows blood to flow freely from the left atrium to the left ventricle. When the left ventricle contracts, the valve closes and only allows blood to flow into the aorta.

Structures of the Heart Pulmonic Valve Is a semilunar valve, and is also called the pulmonary valve Located between the right ventricle and pulmonary artery that leads to the lungs

Structures of the Heart Aortic Valve Is a semilunar valve, and is located between the left ventricle and the aorta

Functions of the Heart Even though the right side and left side of the heart are separated, they work together The active phase is called Systole, and is followed by a resting phase called Diastole

Functions of the Heart Diastole Atrial Systole Ventricular Systole Atria fill with blood which begins to flow into ventricles as soon as their walls relax Atrial Systole Contraction of atria pumps blood into the ventricles Ventricular Systole Contraction of ventricles pumps blood into aorta and pulmonary arteries

Functions of the Heart

Functions of the Heart Cardiac Output The volume of blood pumped by each ventricle in one minute It is calculated by the stroke volume (volume of blood ejected from the ventricle from each beat), and the heart rate (number of times the heart beats per minute)