Heart examination

The closure of the heart valves and the contraction of the heart muscle produce sounds that can be heart through the thoracic wall by the unaided ear, although they can be amplified by means of a STETHOSCOPE. The sounds of the heart may be represented as lubb-dupp- pause -lubb-dupp- pause. The lube sound indicates the closing of the valves between the atria and ventricles and the contracting ventricles; the dupp sounds indicates the closing of semi lunar valves. In addition, there may also be cardiac murmurs. The study of heart sounds and murmurs furnishes valuable information regarding the condition of the heart muscle and valves.

The heart sounds are recorded with the aid of sensitive microphones, so that anomalies of the heart or the valves can be analyzed. The conduction of the contraction stimulus can also be recorded on the body surface by an ELECTROCARDIOGRAPH. The electrocardiograph (ECG) that is obtained in this way furnishes information about the rhythm of the heart, the conduction of the stimulus, and the conduction of the heart muscle. Other methods include the mechanical recording of the heartbeat, echocendiography and radioisotopes, x-ray analysis of the heart’s from and movements, and x-ray contrast studies of the blood flow through the heart and the coronary vessels.

Regulation of Heartbeat

The heart muscle pumps the blood through the body by means of rhythmical contraction (systole) and dilations (diastole). On the heart system there are the heart’s left and right halves work almost synchronously. When the ventricles contract (systole), the valves between the atria and the ventricles close, as the result of increasing pressure, and the valves to the pulmonary artery and the aorta open. When the ventricles become flaccid during diastole and the pressure decreases, the reverse process takes place: through the valves between the atria and the ventricles, which are now open again, blood is drawn from the atria into the ventricles, and the valves to the pulmonary artery and the aorta close.


At the end of diastole the atria also contract and thus help to fill the ventricles. This is followed by systole. The electrical stimulus that leads to contraction of the heart muscle originates in the heart itself, in the sinoatrial node (SA node), or pacemaker. This node lies just in front of the opening of the superior vena cava. It consists of heart cells that emit regular impulses. This electrical stimulus becomes propagated over the muscle cells of both atria and reaches the atrioventricular node (AV node), which lies on the border between the atria and the ventricles. The stimulus continues into the bundle of his, which proceeds for about a centimeter and then divides into a left and aright bundle branch. The two bundle branches lie a long the two sides of the heart’s septum and then proceeds toward the apex. Small side branches that come off are the Purkinje fibers, which conduct the stimulus to the muscle cells of the heart’s ventricles.

The Purkinje fibers differ from the cardiac muscles cells and conduct the stimuli more rapidly. The AV node conduct the stimulus relatively slowly, however. As a result, the heart chambers contract regularly and evenly during systole, and ventricular contraction does not coincide with that of the atria; so the pumping function is well coordinated. Potentially, the whole conduction system is able to discharge spontaneously and can take over the function of the SA node. The rate at which the cells of the SA node discharge under normal circumstances is externally influenced through the autonomic nervous system, which sends nerve branches to the heart and the determines the resultant heart rate. In adults a rest this is between 60 and 74 beats a minute. In infants and young children it may be between 100 and 120 beats a minute. Tension, exertion, or ever may cause the rate of a healthy heart to vary between 55 and 200 beats a minute.

The output of the heart is expressed as the amount of blood pumped out of the heart each minute: the heart minute-volume (HMV). This is the product of the heart rate and the stroke volume (SV), The amount of blood pumped out of the heart at each contraction.

Coronary and Heart Hormone

Coronary Circulation

The blood supply to the heart muscle is furnished mainly by the coronary arteries, which originate from the aorta immediately after the aortic valve. These vessels pass through the fatty tissue beneath the pericardium and then branch out into the heart muscle. Deoxygenated blood is transported from the heart muscle to the right atrium by the coronary veins. The heart’s energy supply is almost completely dependent on the coronary vessels. Only the tissues lying directly beneath the endocardium receive a sufficient amount of oxygen from the blood within the cavities of the heart.

The coronary arteries do not have any effective collateral circulation. That is, each part of the heart depends on its own coronary branch for its blood supply. If a branch becomes partially or completely blocked through various heart diseaseas, the result can be a heart attack or lesser muscle damage. Spasms in the wall muscles of the coronary arteries can also result in obstructions that impede the flow of blood.

Heart Hormone

Like a number of other internal organs, the heart produces a hormone with regulatory effects on other body systems. The heart hormone is called atrial natriuretic factor. The name refers to its origin in the atria and its contributory role in maintaining proper salt and water balance in body, natriuresis being the excessive loss of sodium and other cations in urine. Atrial natriuretic factor also has a strong hypotensive, or lowering, effect on blood pressure and an inhibitory effect on the serection of rennin by the kidneys and of aldosterone by the adrenal cortex. These and other hormonal and neural mechanisms all interact with one another in the control of salt and water levels in the body.

Blood Flow through Heart

The right atrium receives oxygen-poor blood from two major veins: the superior and inferior vena cava, which enter the atrium through separate openings. From the right atrium the blood passes through the tricuspid valve, which consists of three flaps, or cusps, of tissue. This valve directs blood flow from the right atrium to the right ventricle. It remains open during diastole, or ventricular filling; however, when the ventricle contrast, the valve closes, sealing the opening and preventing backflow into the right atrium. Fine cords attached to small muscles (Papillary muscles) on the ventricle’s inner surface prevent the valve’s flaps from being pushed backward (a similar arrangement can be seen on the left ventricle’s mitral valve). From the right ventricle blood is pumped through the pulmonary, or semi lunar, valve, which has three half-moon-shaped flaps, into the pulmonary artery. This valve prevents backflows from the artery into the right ventricle. From the pulmonary artery, blood is pumped to the lungs where it gives up carbon dioxide and receives oxygen, and then is returned to the heart’s left side through four pulmonary veins (two from each lung) to the left atrium and then through the mitral valve, a two flapped valve also called a bicuspid valve, to the left ventricle. As the ventricle contrasts, the mitral valve prevents backflow of blood into the left atrium, and blood is driven through the aortic valve into the AORTA, the major artery, which supplies blood to the entire body. The aortic valve, like the pulmonary valve, has a semi lunar shape and a unidirectional function.

Before birth and additional opening exists in the septum between the left and right atria of the fetal heart. This allows the blood to flow directly from the right to the left atrium without passing through the right ventricle and thus to the lungs, which do not yet function. After birth this opening closes. Additionally, in the fetal heart the ductus arteriosus, a bridge between the pulmonary artery and the aorta, allows most of the blood to bypass the collapsed fetal lungs. The ductus arteriosus atrophies shortly after birth.