Human Body

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).

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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 surp …