Human Body Essay

This essay has a total of 2822 words and 14 pages.

Human Body



In the Beginning
Within a month of conception, the cluster of cells that will, in the course of
time, become a human being begins throbbing, signaling the development of
a primitive heart. Scarcely four weeks more pass before an intricate network
of veins and arteries the size of a pea forms and subdivides into a tiny replica
of the four chambers that will one day make up the adult heart. As the fetus
grows, so does its vitally important circulatory system. Although most of the
functions of the heart remain dependent upon the mother throughout the
entire pregnancy, in the latter stages the organ becomes strong enough to beat
on its own. Even so, until birth the baby is cared for and nourished through
the mother's placenta. An umbilical cord provides a supply line that furnishes
food and oxygen for the baby, and also removes waste. When at last the
birthing moment arrives, the baby emerges a separate individual; almost as
soon as its first cries are sounded, its pulmonary and circulatory systems
undergo a change that renders them self-sufficient.
How it Works
Technically speaking, the circulatory system is a masterpiece of organic
activity. Composed of a network of 60,000 miles of blood vessels and a
pintsized, powerhouse pump known as the heart, it services more than 2,000
gallons of blood per day, feeding and replenishing other organs and making
life possible.
In an adult, the heart is normally an 11 - ounce, fistsized organ that literally
pushes blood through arteries, veins and capillaries. It does this by means of
muscular contractions sparked by electrical impulses from the heart's
pacemaker (sinoatrial node). All of the cells within each of the chambers
magically work on cue. First, the right side sends blood to the lungs.
There carbon dioxide is removed and oxygen is added, turning the blood a
bright red color. Then the blood is pumped to the left side of the heart and
sent via the aorta to the rest of the body.

To survive, each of the body's approximately 1 billion cells must be
nourished. This is the job of the blood, with the heart and vessels acting as
facilitators. After depositing the necessary nutrients with each of the cells, the
blood returns to the heart, carrying with it waste products it has picked up
along the way. These are eliminated through a filtering process in the lungs
and kidneys.

By now the supply of oxygen within the blood is nearly exhausted, and it is
time to restock its supplies and begin the journey again. Incredibly, the whole
process has taken just 20 seconds.

During the course of an average life, the heart pumps tens of millions of
gallons of blood. It is estimated that the amount would easily fill a
24-foot-wide cylinder to a height greater than the Empire State
Building.
Perhaps more impressively, the circulatory system has the computer-like
ability to direct greater and lesser amounts of blood to various areas of the
body according to their immediate needs. This explains why athletes often
forego eating just prior to a match. During the process of digestion, the
gastric organs require more blood to complete their work. As if that weren't
enough, the heart is also wired through the nervous system to respond to a
large variety of physical and emotional stimuli. Witness the quickening of the
heart at the touch of a loved one.

What Can Go Wrong

Most circulatory problems are caused by a blockage in an artery, which is
known as atherosclerosis or hardening of the arteries. No one knows for sure
why this happens, but the prevailing theory states that something causes the
protective inner lining of an artery wall to be injured. Once impaired, the
collagen in the lining is exposed. That, in turn, attracts platelets and toxic
substances from the bloodstream, which enter the artery wall. Eventually, the
process leads to a buildup of debris, narrowing of the artery and finally,
blockage.
Interestingly enough, although the heart has a continual flow of blood
streaming in and out of its chambers, it is unable to take the nourishment it
needs from this source. Rather, it must rely on its own miniature circulatory
system, which branches off from the aorta or main channel. Here tiny but
extremely important vessels called coronary arteries provide the means to
feed the heart. Like other arteries, they are also subject to blockage. And
herein lies a potential and fairly common tragedy, because when coronary
arteries cease to function as they should, the heart is deprived of the oxygen
and nutrients it needs. Starved, it becomes damaged and, at worst, dies.

There are several factors that contribute to circulatory problems, including
high blood pressure (hypertension), high levels of cholesterol in the
bloodstream, smoking, obesity, heredity, lack of exercise and emotional
stress.
Blood pressure refers to the force at which blood courses through arteries and
veins as it 'journeys to the various parts of the body. It is determined by the
total amount of blood in the body (which may vary from individual to
individual and even time to time), the intensity at which the heart has to
work, and the resistance to flow offered by the artery walls. When blood
pressure is elevated above a safe level, it can speed up the process of
damaging the blood vessels. It can also lead to personality changes and may
affect the heart, brain and kidneys.
Cholesterol Management

Cholesterol is a type of animal fat that is either manufactured by the liver or
absorbed through the diet. Although most often it is described in villainous
terms, it is actually necessary in some forms for good health. Cholesterol
helps the body metabolize carbohydrates and manufacture its own vitamin D.
It also is a prime supplier of certain essential hormones. However, problems
occur when cholesterol and other fats start lining the insides of arteries,
narrowing them and making them susceptible to deposits of plaque. This
hampers the flow of blood, and consequently, the supply of life-giving
nutrients and oxygen.
Do you know what your cholesterol level is? When was the last time you had
it checked? Or have you ever had it checked? How are you doing with your
cholesterol management? And do you need to be concerned about it?

Let's look at some statistics
The average American eats 165 pounds of meat, 276 eggs, 17 pounds of
butter or margarine and 18 pounds of ice cream annually. Daily, the average
American consumes the equivalent of a full stick of butter in fat and
cholesterol. This diet contributes to a 1-2% increase in the cholesterol
accumulating in the arteries each year. Remember, high cholesterol levels are
not something you can feel. To determine if your blood cholesterol level is
contributing to your risk of heart disease, have it tested by a qualified health
professional through laboratory analysis. Cholesterol is manufactured in the
liver and is absorbed from the diet. S nce the major lipids or fats are not
soluble in blood, they are carried in the bloodstream by protein carriers called
lipoproteins. These lipoproteins vary in size and are termed highdensity
lipoprotein (HDL), low- density lipoprotein (LDL) and a very low-density
lipoprotein (VLDL).
All cholesterol is not responsible for heart disease. HDL and LDL mainly
carry cholesterol and play opposite roles in the body. HDL's are the heaviest
and have the greatest amount of protein. As they move through the body, they
are able to collect cholesterol and transport it to the liver. There, the
cholesterol is processed and then removed. Since it tends to clean up excess
cholesterol, HDL has been called a scavenger. LDLs, on the other hand, take
cholesterol from the liver to cells, where it is used for hormone synthesis.
LDL is also a constituent of cell membranes, or arterial plaque deposits. High
LDL levels can contribute to atherosclerosis.
A ratio of at least one LDL to three HDL is desirable for circulatory system
health. Obesity and a sedentary lifestyle are chiefly responsible for a
reduction of HDL levels. HDL levels can be raised through reducing dietary
fats and cholesterol, increasing aerobic exercise, not smoking and
maintaining ideal body weight. The American Heart Association reports that
ideal cholesterol ranges are 130-190 mg / dl. Clinical studies have identified
that cholesterol levels higher than 200 mg / dl are related to rapid increases in
the incidence of cardiovascular disease. It has been estimated that one-half of
American males exceed the limit. People with blood cholesterol levels higher
than 265 mg / dl have four times the risk of developing heart disease than
those with levels below 190 mg / dl. Cholesterol management is the "Big
Three" risk factor most related to nutritional factors. The FDA Consumer
reported, "The consensus of medical opinion is that high blood cholesterol is
related to the development of coronary artery disease, and that changes in diet
could help reduce this risk factor."

Cutting back your intake of animal foods will cut back your intake of
dietary cholesterol. Plants contain no dietary cholesterol.
In addition, fat-modified diets can lower blood cholesterol by 30 percent or
more. Reducing dietary fat is centered around reducing saturated fat intake.
A surprising source of saturated fat may be the nondairy creamer used in
coffee. A study by University of Nebraska Medical Center professors found
that 22 out of 25 non-dairy creamers contained coconut oil. Coconut oil is
more saturated than cream, butter, lard or beef fat. Be aware of other
prepared foods containing coconut oil.

Another important consideration is increasing the ratio of polyunsaturated
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