Hearth

Diastole

________ is the longer of the two phases so that the heart can rest between contractions.

rhythmic noises

The ________ accompanying heartbeat are called heart sounds.

left atrium

Oxygenated blood is returned to the ________ through the pulmonary veins.

low pressure circuit

right atrium

Pressure is reduced in the capillaries (vessels of minute diameter) and is reduced further in the veins returning blood to the ________.

outset of systole

It is caused by pressure exerted on the chest wall at the ________ by the rounded and hardened ventricular wall.

heart cavity

The ________ is divided down the middle into a right and a left heart, which in turn are subdivided into two chambers.

Electrical impulses

________ are conducted from the sinoatrial node to the atrioventricular node and bundle of His, through the bundle branches, and into the ventricles.

Murmurs

________ may indicate that blood is leaking through an imperfectly closed valve and may signal the presence of a serious heart problem.

tough muscular

The heart consists of several layers of a(n) ________ wall, the myocardium.

period of relaxation

The ________ is called diastole.

impulse

A(n) ________ from the S- A node causes the two atria to contract, forcing blood into the ventricles.

lungs amphibians

In animals with ________, reptiles, birds, and mammals- the heart shows various stages of evolution from a single to a double pump that circulates blood to the lungs and to the body as a whole.

muscular partition

In humans it is situated between the two lungs and slightly to the left of centre, behind the breastbone; it rests on the diaphragm, the ________ between the chest and the abdominal cavity.

ventricular wall

Occasionally audible in normal hearts is a third soft, low- pitched sound coinciding with early diastole and thought to be produced by vibrations of the ________.

Coronary heart disease

________, in which an inadequate supply of oxygen- rich blood is delivered to the myocardium owing to the narrowing or blockage of a coronary artery by fatty plaques, is a leading cause of death worldwide.

right atrium

The ________ receives venous blood from the head, chest, and arms via the large vein called the superior vena cava and receives blood from the abdomen, pelvic region, and legs via the inferior vena cava.

Normally, two distinct sounds are heard through the stethoscope

a low, slightly prolonged "lub" (first sound) occurring at the beginning of ventricular contraction, or systole, and produced by closure of the mitral and tricuspid valves, and a sharper, higher-pitched "dup" (second sound), caused by closure of aortic and pulmonary valves at the end of systole