Heart
The heart is a muscular organ whose interior is divided into two pairs of
chambers, one on the right, the other on the left; the chambers of each
pair are connected with each other by a valve. Lying in the mid-left
section of the chest, close to the breastbone, the human heart weighs about
12 ounces, beats 70 to 80 times a minute, and is enclosed by a sturdy
membrane called pericardium. Its chambers are lined by a delicate membrane,
the endocardium, and its vigorous muscular and connective tissues are
nourished by the heart’s own blood vessels, the coronary vessels.
How the Heart Works
This remarkable muscle serves as a pump controlling the blood stream in two
circuits, the pulmonary and the systemic. The right side of the heart
receives the blood from the large veins that drain the systemic circuit and
propels it into the lungs where carbon dioxide is removed and oxygen is
picked up. The oxygenated blood, collecting in the pulmonary veins, than
enters the left side of the heart, from which it is pumped out again into
the systemic circulation by way of the body’s largest blood vessel, the
aorta. The rhythmic pumping is in the form of a repeated contraction (
systole ) and relaxation (diastole). Every 60 seconds, this precisely
adjusted human pump drives about five quarts of blood through the body.
Auricles and Ventricles
The four chambers of the heart have special roles in the pumping process.
The upper chambers are called the auricles; the lower chambers, the
ventricles. The auricle and ventricle on each side together form an
independent part of the heart, somewhat like a duplex apartment; in effect,
they make up a “right heart” and a “left heart”. There is no connection for
the blood into the pulmonary circuit, the left into the general body
circuit.
Valves of the heart
Between the right auricle and right ventricle is a valve, called the
tricuspid valve. Similarly, the left auricle and left ventricle are
connected by the mitral valve, so named because of its apparent resemblance
to a bishop’s miter or tall cap. The sounds of the valves opening and
closing are heard by the doctor when he listens with his stethoscope. In
addition to the valves between auricle and ventricle on each side of the
heart, there are valves at the blood’s exit points: the pulmonary valve
opening from the right ventricle into the pulmonary artery, and the aortic
valve opening from the left ventricle into the aorta. All these valves,
both within the heart and leading out of it, open shut in such a way is to
keep the blood flowing only in one direction through the heart’s two
separate pairs of chambers: from auricle to ventricle and out through its
appropriate artery.
A Single Pumping Action
Although the right and left sides of the heart serve two separate branches
of the circulation, each with its distinct function, they are co-ordinated
so that the heart efficiently serves both sides with a single pumping
action. The valve action on both sides is also co-ordinated with the two
phases of the pumping action. Thus, during the diastole, or relaxation
phase, the oxygen-poor blood which was accumulated in the right auricle
returning from the systemic or body circulation pours into the right
ventricle. At the same time, the oxygen-rich blood which was accumulated in
the left auriclereturning from the pulmonary circulation pours into the
left ventricle. The weak walls of both auricles contract to press the blood
into the relaxed ventricles. In the next or contraction phase, the systole,
the valve between auricle and ventricle on each side closes, and the
muscular walls contract the ventricles and sweep the blood through each
passage into the pulmonary artery and the aorta. At the end of the
contraction the pulmonary and aortic valves snap shut, preventing any
backward surge of the blood to the ventricles. The diastole follows, the
ventricles again fill with the flow from their separate auricles and the
cycle is repeated. This co-ordinated rhythmic action goes on tirelessly day
and night throughout every individual’s lifetime.
The Valve Cusps
The valves, which must withstand considerable pressure, are composed of a
special type of tough tissue. The mitral valve, between the left auricle
and ventricle, has two cusps or leaflets. The tricuspid valve, between the
right auricle and ventricle, has three cusps. Both valves function in the
same manner. When blood pressure in auricle is higher than in the
ventricle, the valve leaflets are swept open; as the blood flows downward,
the auricular contraction at the start of the heart beat helps to push the
blood along. As the blood fills the ventricle, the leaflets close, and with
the contraction of the ventricle, pressure tightly shuts the valve. The
valve leaflets are bolstered from below by a set of tough tendons with
muscular attachments, enabling the leaflets to withstand the pressure and
keep the valves from opening inward into the auricle.
The two valves which control the exit passages from the heart, the aortic
valve and the pulmonary valve, have three leaflets each, and they also only
for one-way flow. Other valves at special stations along the line in the
circulatory system keep the blood from pooling in the lower extremities of
the body.
Heart Disease.
Heart disease, the leading cause of death, is a term covering a variety of
more than 20 different diseases of the heart and blood vessels. The most
common of these are rheumatic heart disease, hypertension or high blood
pressure, and coronary artery disease. Other forms of heart disease can be
caused by congenital malformations of the heart and major vessels,
syphilis, diphtheria, abnormal functioning of the thyroid gland, or
diseases resulting from vitamin deficiencies.
Although approximately ten million Americans have some form of heart
disease, the tremendous advances made by medical science have made it
possible to treat and control these illnesses with increasing success. The
majority of individuals who suffer a heart attack recover, and recurrent
attacks of rheumatic fever which injure the heart can now frequently be
prevented. By means of modern surgical techniques, heart defects and heart
damage may often be repaired by HEART SURGERY.
To clarify various descriptions of heart ailments, it should be understood
that a “heart attack” is not strictly the same as “heart disease”. A heart
attack usually signifies the sudden obstruction of a coronary artery, one
of the blood vessels feeding blood to the heart muscle; the clogging of the
artery by a blood clot cuts off the blood supply to an area of the heart
muscle. There is also a distinction between a heart attack, heart disease,
and “heart failure”. Heart failure does not mean that the heart has stopped
beating but that the heart is not pumping efficiently and the body’s blood
circulation is being affected by the change.
One of the most prevalent of the diseases involving the heart is
arteriosclerosis, commonly known as hardening of the arteries. Diseases of
other organs of the body can also produce heart disease; one of these is
nephritis, a disease of the kidneys which affects the tiny blood vessels or
capillaries. Another such disease is diabetes which in some individuals may
injure the blood vessels in much the same fashion as does high blood
pressure.
Symptoms
Symptoms of heart disease may include certain types of palpitation,
shortness of breath, a particular type of chest pain in the region of the
left breast (angina pectoris), swelling of the ankles and feet, dizziness,
fainting spells, extreme weariness, bluish lips, coughing up of blood, or a
persistent cough. A person suffering from such symptoms should consult a
doctor to determine whether heart disease is present. After taking the
patient’s medical history and making a thorough examination, which may
include an electrocardiogram, the doctor will diagnose the condition and
prescribe any treatment that may be required.
Palpitations
An unusually rapid, strong, or irregular heartbeat of which a person is
aware is called palpitation. In the majority of cases, palpitation is
completely normal; almost everyone, for example, feels his heart pounding
more rapidly and strongly after exertion or when he is excited or nervous.
Many people are also apt to be especially conscious of heartbeat when they
are lying in bed, especially when lying on the left side. There are also
palpitations that are abnormal but that do not of themselves indicate heart
disorder, though they may cause annoyance or discomfort. Commonest is the
“skipped beat”, or extrasystole; in some cases this may occur because of
excessive smoking o coffee drinking or as a reaction to some kinds of
medicine.
The various types of palpitation that may indicate heart disorder in some
instances include paroxysmal tachycardia and “flutter”, abnormal rhythms in
which the heart executes runs of rapid beats. Another is auricular
fibrillation, in which the beats are rapid but irregular, seeming to occur
at random.
These palpitations may be caused by organic heart disease, but they also
can result from other factors. Similarly, emotional pressures rather than
organic changes may cause the so-called “nervous heart”, or functional
heart disease. Although these symptoms do not prove definitely that the
heart is in a trouble, they should prompt a person to consult his doctor.
If the doctor’s examination shows no heart disease, the individual can be
reassured. If not, the doctor will be able to begin immediate treatment.
Shortness of Breath
This may occur after only moderate exercise, such as climbing one flight of
steps. A person who finds himself continually in a breathless state after
activities which he once did without efforts should consult a physician.
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