how does heart works?

The Heart

Structure

The heart is a hollow muscular organ which consists of cardiac muscles. It is situated in the middle of the chest cavity, just above the diaphragm and between the two lungs. It is cone-shaped and as big as the owner's closed fist in size. It is covered with a double layered membranous sac called pericardium, which is thin and transparent.

A narrow cavity between two layers is called pericardial cavity. It is filled with a watery fluid called pericardial fluid. The fluid performs two main functions. They are:

·     It allows frictionless movement of the heart.

·     It protects the heart from mechanical injury and shocks. 

The internal structure of the heart shows a muscular layer called septum, which divides the heart into two parts longitudinally. They are right part and left part. These two parts are further divided into two part each. two The right part is divided by tricuspid/right autrioventricular valve and the left part is divided by bicuspid/mitral/left autrio-ventricular valve. In this way, human heart is four-chambered. The upper chambers are called auricles oratria and the lower chambers are called ventricles. The right auricle has venacava and the right ventricle has pulmonary artery and pulmonary valve. The left auricle has pulmonary veins and the left ventricle has aorta and aortic valve.

Working method of the heart 

The main function of the heart is to pump blood into different parts of the body by the rhythmic contractions and relaxations of the auricles and the ventricles. The contraction phase of the ventricles of the heart is called systole and the relaxation phase is called diastole.

When the auricles contract, the ventricles relax. It makes the deoxygenated (impure) blood from the right auricle pass into the right ventricle by opening the tricuspid valve. Similarly, oxygenated (pure) blood from the left auricle passes into the left ventricle by opening the bicuspid valve. At this time, the pulmonic valve and the aortic valve are closed to block the backflow of blood from the arteries to the ventricles.

 After this, when auricles relax and ventricles contract, the impure blood from different parts of the body is brought into the right auricle through the venacava and pure blood is brought into the left auricle through the pulmonary veins. In the mean time, impure blood of the right ventricle passes into the lungs for its purification through the pulmonary artery by the opening of the pulmonic valve. Similarly, the pure blood of the left ventricle is pumped into different parts of the body through the aorta by opening the aortic valve.

The contraction and relaxation of ventricles is called heartbeat. The number of contraction and relaxation of ventricle in one minute is called heartbeat rate. In an adult, the normal rate is 72 to 80.The heart contracts about 72 to 80 times per minute normally but this rate increases to 100 or more during exercise and excitement. The total volume of blood in a normal person is about 5 to 6 litres. Approximately, 5 litres of blood is pumped out by the heart every minute.

Blood Vessels

Blood vessels are hollow and tubular vessels through which blood flows. They circulate the blood from the heart to the body tissues and from the tissues to the heart. The blood vessels are of the following three types:    

·     Arteries

·     Veins                  

·     Capillaries    

·     Arteries

The blood vessels which carry the blood away from the heart are called arteries. They are thickly walled and elastic in nature. They are deep seated in the body and have no valves. The blood flows at high pressure and high speed in arteries. The arteries mainly carry pure blood from the heart to the capillaries except the pulmonary artery. The pulmonary artery carries impure blood from the heart to the lungs for its purification. The arteries are divided into arterioles. The arterioles give extremely thin and fine branches called capillaries.

·     Veins

The blood vessels which bring the blood into the heart from different parts of the body are called veins. They are thin-walled structures with little musculature. They are less elastic in nature and blood flows at low pressure with low speed in them. The valves present in them prevent the back flow of blood. They superficial in our body. They carry impure blood, except the pulmonary veins.

·      Capillaries

Capillaries are formed as a result of the branching of the arterioles. They are a very fine networks of blood vessels. They connect the arteries to the veins. These capillaries reunite to form venous capillaries from which venules emerge. A number of such venules unite to form a vein. However, capillaries provide a definite path for the flow of blood. 
As we know, blood flows at high pressure in the arteries. When the blood enters the capillaries the blood pressure increases in it. Because of this pressure, the walls of the capillaries expand and the pores on them become large, through which molecules of glucose, water, oxygen, hormones, etc. arc filtered out. In this way, cells and tissues get the required things from the blood.   

 

·     Blood circulation

 The human heart has four chambers with double circulation systems, which means blood passes twice through the heart to supply once to the body. The circulation of blood in humans takes place through two routes mainly. They are systemic circulation and pulmonary circulation.

·     Systemic Circulation

The circulation of blood between the heart and different parts of the body other than the lungs is called systemic circulation.

When the ventricles contract, the oxygenated blood from the left ventricle is pumped to different parts of the body through the aorta. After providing the necessary components to the cells and tissues, the blood returns to the right auricle with the waste materials through the superior and inferior venacavas. The auricles are relaxed in this situation.

·     Pulmonary circulation

Heartbeat

The contraction and relaxation of the heart muscles pump the blood. The combined term of one contraction and one relaxation of the heart muscles is called a heartbeat. The number of heartbeat in one minute is called heartbeat rate.

The normal heart beat rate in an adult is about 72-80 times per minute, but the rate varies according to the position of the body. It is faster while walking, during exercise, excitement, fever, etc. The heartbeat rate is equal to the pulse rate of a person.

 Blood Pressure

 The pressure exerted by the flow of the blood on the walls of the arteries is called blood pressure. Blood pressure is systolic and diastolic.

Systolic pressure is the pressure of blood on the artery of that condition of the heart when ventricles are contracted. It is the maximum pressure of blood on the wall of the arteries. In a healthy person, its value is 100-140 mm of Hg.

Diastolic pressure is the pressure of blood on the artery of that condition when the ventricles are relaxed. It is the minimum pressure of blood on the wall of the veins. In a healthy person, its value is 60—90 mm of Hg. Blood pressure is greater during systole than during diastole. Blood pressure is measured by an instrument called sphygmomanometer. If the blood pressure of a person is 120/80 mm of Hg, it means their systolic blood pressure is 120 mm of Hg and diastolic blood pressure is 80 mm of Hg. The blood pressure varies with age, heavy work, excitement, exercises, etc. It is also influenced by the heartbeat. A rise in blood pressure called high blood pressure while a fall in blood pressure is called low blood pressure. Some diseases related to blood circulatory system

a.                High blood pressure

If the blood pressure is more than the normal blood pressure, it is called high blood pressure. When the lower limit of blood pressure exceeds 90 mm of Hg and the upper limit of blood pressure exceeds 140 mm of Hg, it is termed as high blood pressure. It is also called hypertension.

Causes of high blood pressure

The major causes of high blood pressure are as given below

1. It is caused by smoking.

2.  Overweight or obese is another major cause of high blood    pressure.

3.            Lack of physical activities.

4.            More amount of salt in diet.

5.            Too much consumption of alcohol.

6.            Stress also promotes high blood pressure.

7.            Older age and hereditary cause.

8.            Sometimes chronic kidney diseases and thyroid disorders also become the cause of high Blood pressure.

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10.    More use of fatty, spicy and fried food.

Prevention of high blood pressure

We can prevent high blood pressure in the following ways.

·    Eat a better diet with less amount of salt.

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·    Maintain the weight.

·    Be a positive thinker and manage stress.

·    Avoid tobacco chewing or smoking.

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By the above activities, we can reduce blood pressure. The above activities also lower the risk of heart attack, heart diseases, stroke and kidney disease.

b.             Diabetes

Diabetes is a disease that causes imbalance in the level of sugar in blood. It is called diabetes mellitus by doctors. In this disease, the patient has a high level of sugar in blood. The pancreas is a mixed gland that produces a hormone called insulin. When the pancreas produces less insulin, the sugar level increases in blood. Before meal, normal sugar level in blood is 70-99 mg/dl.

The postprandial sugar taken 2 hours after meal should be less than 140 mg/dl. If the sugar level crosses the limit, it causes diabetes. The symptoms of the disease are as follows:

·    Frequent urination (polyuria).

·    The patient becomes increasingly thirsty (polydipsia).

·    The patient feels hungry frequently (polyphagia)

·    Slow healing of wounds.

·    Fall in body weight and dizziness.

Prevention of diabetes mellitus

Even though there is no complete cure of some causes of diabetes, it can be managed through some change in lifestyle. A combination of exercise, diet and body weight control helps to control diabetes. The following activities help to prevent diabetes.

·    By changing lifestyle (food and exercise).

·    By reducing body weight.

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·    By including green vegetables and fruits in food.

·    By regular exercise. Meditation also help to control diabetes.

c.              Uric acid

We eat food like liver, dried beans, peas, salt, fish, and drink beer. They contain purines. When the purines break in our body, they form uric acid. Most of the uric acid dissolves in blood and is transported to the kidneys. From there, it is passed out in the form of urine. If the body produces too much uric acid or the proper amount of uric acid is not removed from the body, it makes us sick.

The high level of uric acid in blood is called hyperuricemia. Normal value of uric acid in blood ranges between 3.5 and 7.2 mg/dl. The excess amount of uric acid in blood causes gouty arthritis. The high concentration of uric acid changes into urate crystals. The crystals deposit around the joints and soft tissues and resist the movement of the joints. It affects ankles, heels and toes. Gout can cause permanent damage to the joints and the kidneys.

Causes of gout

The major causes of gout are as given below:

·    Family history of gout.

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·    Kidney disorders.

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Prevention of uric acid

There are many preventive measures of hyperemia. Some of them are mentioned below.

·    Apple cider vinegar is used with water to drink to reduce uric acid level.

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·    Cherries as well as purple and blue coloured berries contain anthocyanins, which help to lower uric acid.

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·    The victim should drink plenty of water.

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·    More dairy products should be used.

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Beside the above points, use of alcohol and fatty food should be avoided. Regular exercise and maintaining normal body weight also prevent uric acid.