A. Structure and Function of the Heart

 

 

 

 

 

 

 

 

 

The Heart


The heart is a hollow muscular organ with openings into the arteries and from the veins. In the diagrams of the circulation, the heart is opened out to show how the blood passes through it. It is about 3 ½ inches wide at its broadest part, 5 inches long, and 2 ½ inches thick. Its location is suspended in the chest cavity by the large blood vessels, with its base resting on the diaphragm. The heart of a healthy 70-kilogram person pumps about 7,200 liters of blood everyday at a rate of 5 liters per minute. During short periods of exercise, the rate of the blood pumped increases several folds.

The heart pumps blood through the circulatory system along two major pathways, the arteries and veins. The arteries generally carry oxygen-filled blood and nutrients from the left side of the heart to most body tissues. The veins generally carry deoxygenated blood and carbon dioxide back to the right side of the heart. A special network of coronary arteries carries oxygen-rich blood for use by the heart itself.

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Structure of the Heart

The heart is divided into a right and left side by a muscular wall called the septum. Each side is divided horizontally into two sections, for a total of four chambers: the right and left atria and the right and left ventricles.
 
Valves control the flow of blood between the chambers of the heart. Atrioventricular valves, as the name implies, separate the atria from the ventricles:
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Function of the Heart

The heart functions as a pump and is responsible for the circulation of the blood through the blood vessels. It is responsible for making blood flow through the blood vessels.

The circulation of the blood starts from the arteries, which carry blood from the heart. The aorta sends branches to the heart, head and arms, then it gives out branches to the internal organs. After that, it divides into two arteries that carry blood to the legs and feet.

The blood reaches the right side of the heart through two big veins: the superior and inferior vena cava to the right atrium. In the right atrium, most of the blood passed into the right ventricle relaxes following the previous contraction. The right atrium then contracts thus push the remaining blood to the right ventricle.

The contraction of the right ventricle pushes blood against the tricuspid valve, forcing it closed, and against the pulmonary semilunar valve, forcing it to open, thus allowing blood to enter the pulmonary trunk. The pulmonary trunk branches to form pulmonary arteries, which carry blood to each lung. In the lungs, the blood exchanges carbon dioxide for oxygen through the walls of many capillaries.
 
Then blood flows to the left side of the heart in the pulmonary veins. After passing through the lungs, the blood enters the left atrium through the pulmonary veins. The blood passing from the left atrium to the left ventricle opens the bicuspid valve, and the contraction of the atrium completes left ventricular filling. Contraction of the left ventricle then pushes blood against the bicuspid valve, closing it, and against the aortic semilunar valve and then goes to the aorta.

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B. Pathiophysiology of Cardiovascular Disease

ATHEROSCLEROSIS
Commonly called "hardening of the arteries", it is a progressive disease that causes the arteries to become narrowed and the walls of the arteries to lose elasticity. Here, arteries are narrowed and hardened when cholesterol and fats build up in the walls of the arteries. It can form in any of the arteries in the body.
 
When there is atherosclerosis in the coronary arteries, the heart muscle does not receive the blood and nutrients it needs, this leads to angina pectoris, and possibly heart attack.

HYPERTENSION
Hypertension the medical name given to high blood pressure. When you have hypertension, the blood vessels become tight and constricted, forcing your heart to pump harder to move blood through your body. These changes cause the blood to press on the vessel walls with greater force. Over time, fatty deposits may build up along the walls and cause hardening of the arteries. This process is called atherosclerosis. The heart must work even harder to pump blood through these hardened arteries. Sometimes blood clots form on these narrow arteries, causing a heart attack or stroke.

· defined in adult as a blood pressure greater than or equal to 140 Hg systolic pressure and greater than or equal to 90 mm Hg diastolic pressure.

CORONARY HEART DISEASE
Coronary heart disease, the most common type of heart disease in most industrialized countries, is responsible for nearly 500,000 deaths in the United States yearly. It is caused by atherosclerosis, the buildup of fatty material called plaque on the inside of the coronary arteries. Over the course of many years, this plaque narrows the arteries so that less blood can flow through them and less oxygen reaches the heart muscle.

The most common symptom of coronary heart disease is angina pectoris, a squeezing chest pain that may radiate to the neck, jaw, back, and left arm. Angina pectoris is a signal that blood flow to the heart muscle falls short when extra work is required from the heart muscle. An attack of angina is typically triggered by exercise or other physical exertion, or by strong emotions.

Coronary heart disease can also lead to a heart attack. In a heart attack, part of the heart muscle dies because it is deprived of oxygen. This oxygen deprivation is also responsible for the crushing chest pain characteristic of a heart attack.

Coronary heart disease was once thought to affect primarily men, but this is not the case. The disease affects an equal number of men and women, although women tend to develop the disease later in life than men do.

Coronary heart disease cannot be cured, but it can often be controlled with a combination of lifestyle changes and medications. Patients with coronary heart disease are encouraged to quit smoking, exercise regularly, and eat a low-fat diet.

CONGENITAL DEFECTS
About 8 of every 1,000 babies in the United States are born with a congenital heart defect. One of the most common abnormalities is a septal defect, an opening between the right and left atrium or between the right and left ventricle. In babies with these abnormalities, some of the oxygen-rich blood returning from the lungs is pumped to the lungs again, placing extra strain on the right ventricle and on the blood vessels leading to and from the lung.

An infant may be born with several different heart defects, as in the condition known as Tetralogy of Fallot. In this condition, a combination of four different heart malformations allows mixing of oxygenated and deoxygenated blood pumped by the heart. Infants with tetralogy of Fallot are often known as "blue babies" because of the characteristic bluish tinge of their skin, a condition caused by lack of oxygen.

ARRYTHMIAS
Arrhythmias, or abnormal heart rhythms, arise from problems with the electrical conduction system of the heart. Arrhythmias can occur in either the atria or the ventricles.

Some people have minor arrhythmias that persist for long periods and are not dangerous-in fact, they are simply heartbeats that are normal for that particular person's heart. A temporary arrhythmia can be caused by alcohol, caffeine, or simply not getting a good night's sleep.

Arrhythmias may involve either abnormally slow or abnormally fast rhythms. However, the rhythm they generate is slow, often only about 40 beats per minute. An abnormally slow heartbeat is dangerous if the heart does not pump enough blood to supply the brain and the rest of the body with oxygen. In this case, episodes of dizziness, lightheadedness, or fainting may occur. Some types of abnormally fast heart rhythms are usually not dangerous. Others may be controlled with medications.
 
 
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C. Risk Factors

Risk Factors that are Uncontrollable:

Risk Factors You Can Control:

 

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D. The Role of Exercise

If exercise doesn’t burn many calories, and if it doesn’t contribute significantly to causing fat loss, what role does exercise have in the fat loss process? Exercise provides the following 6 contributions to a fat loss program. The first three and most important of these contributions can only be provided by strength training (weight lifting). Neither aerobic activity, nor any other physical activity is of any real value. The contributions of exercise are listed in order of importance.
 
  1. Discriminate Weight Loss
  2. Increased Basal Metabolism
  3. Improved Body Shape and Appearance
  4. Continued Preoccupation
  5. Depressed Appetite
  6. Increased Caloric Expenditure

Discriminate Weight Loss: Weight loss per se’ is not the objective. What the scale indicates is of no relevance. Fat loss is what matters. A calorie deficit created in the absence of strength training will result in the loss of valuable lean tissues (muscle, organ tissue, and water). Some studies have shown that diet alone without exercise results in more muscle loss than fat. Aerobic activity also fails to prevent the loss of muscle. Strength training exercise, and only strength training, causes the body to selectively lose fat and spare muscle.

Increased Basal Metabolism: Basal metabolism describes the amount of energy (calories) your body expends each day for all its basic life sustaining functions. Essentially, it is the base level of energy expenditure to sustain life. It does not include extra calories expended during physical activity. In addition to preventing a loss, strength training causes an increase in lean muscle tissue. Muscles have a high energy requirement to sustain them. Therefore, as muscle tissue is increased, basal metabolism increases. The body then requires additional calories each day to support basic physiological functions. This allows a higher calorie intake without fat gain, a higher calorie intake that still results in fat loss, and a higher calorie intake for fat maintenance.

Improved Shape and Appearance: When muscles become stronger they become firmer and possess better muscle "tone". Their shape, contour, and definition also improves. All these attributes enhance overall body shape and appearance.

Continued Preoccupation: You can’t eat and exercise and/or perform physical activity at the same time. Therefore, by preoccupying you, exercise can assist in prevention of excess food consumption.

Depressed Appetite: Physical activity, especially exercise, depresses appetite. However, this factor is of limited value due to its temporary effect. Hunger returns after the body has recovered from the bout of exercise.

If you develop a craving for food, get up and take a walk, clean the house, or wash the car. These activities do not qualify as exercise, nor do they burn much in the way of extra calories, but they will depress your appetite and keep you preoccupied.

Increased Caloric Expenditure: Increased caloric expenditure is by far the slightest and least important contribution of exercise to a fat loss program. Its contribution is so insignificant that it hardly deserves mention. Ironically, increased caloric expenditure receives the most attention by the press, health care professionals, and the general public. This is indicative of how out of touch with reality people are in regard to the facts of fat loss.

It has already been illustrated how few extra calories are expended by exercise. So few that you should not even consider them in your program. Far better, more time efficient results are achieved by restricting calorie intake and performing two brief, but intense, strength training workouts each week.

 

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So...what is fat, really???

Fat is a major source of calories or energy. Fat improves the taste and odor of foods and gives a feeling of fullness. Fats form the structures in our bodies, including muscles, nerves, membranes and blood vessels and are essential for the absorption of fat-soluble vitamins A, D, E and K in the body .

Although some fat in the diet is necessary, too much fat can lead to heart disease, obesity and other health problems. There are three kinds of fat: saturated fat, polyunsaturated fat and monounsaturated fat. Fats in the diet may be of animal (saturated) or vegetable (unsaturated) origin. Examples of fat in the diet are gravy, bacon, margarine, butter, cream, salad dressings and nuts. Meats and some milk products also contain significant amounts of fat. The guidelines recommended by the American Heart Association and the Surgeon General's Office suggest that fat should contribute no more than 30% of total calories. For those adults with heart disease a diet of 20 percent or even 10 percent of calories from fat is advised. The fat we eat is saturated and unsaturated. These terms refer to the chemical structure of the fat molecules. A low total fat intake, with the majority of fat from unsaturated sources, appears to lower blood cholesterol levels. Too much of any of these fats will increase dietary fat intake, and excess body fat may increase cholesterol levels and the potential to increase body fat.

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