Human heart is a muscular, cone shaped , hollow dark red colour organ about the size of fist .It plays the role of pump in the circulatory system. Heart is situated behind the sternum, between the lungs in the thoracic cavity. The heart is slightly tilted towards the left. In man heart weighs 0.43 % of the body weight .

The heart is covered in the tough inflexible membrane called as pericardium. Between heart and the pericardium their is present pericardial fluid which help to reduce friction between the heart wall and surrounding tissue. The heart is made up of special types of muscles called as myocardium. The inner lining of heart is called as endothecium.

Internal Structure of Human Heart :

Human heart consists of basically four chambers. The upper chamber are called the auricle or the atrium and the lower two chamber are called the ventricles.

The two auricles are separated from each other by interauricular septum and the two ventricles are separated by interventricular septum.

The ventricle have more muscular wall than the auricles. The right auricle opens into the right ventricle . This opening is guarded by a tricupsid valve.

The left auricle opens into the right ventricle which is guarded by a bicupsid valve. Both these valve prevent the back flow of the blood to the auricle during pumping action.

Heart consists of different types of vessels like :-

Superior vena cava : It brings blood from the body parts superior to the heart,

Inferior vena cava: It brings blood from the parts of the body inferior to the heart ,

Pulmonary artery : It carries blood to the lungs for oxygenation.

Coronary sinus : It drain blood from the vessels supplying the walls of the heart.

Aorta: It takes blood away from the heart to all other body parts except the air sacs of the lungs.

Pulmonary vein : It brings oxygenated blood to the heart fro the lungs.

Working of Heart :-

The right atrium receives the deoxygenated blood from all the body parts through veins like superior vena cava and inferior vena cava.

When the right atrium is full of blood and it contracts , the tricupsid valves open under the pressure and the blood is delivered to the right ventricle . This valve help in preventing back flow of the blood.

When right ventricle is full of blood and the ventricle contracts , the blood is pumped into the pulmonary artery which carries the blood to the lungs for oxygenation.

At the junction of right ventricle and pulmonary artery their is present a semilunar valve which prevents the back flow blood.

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Sample Questions

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Question : 1

How many chambers are present in the human heart?
A. One	B. Two	C. Three	D. Four
Right Option : D
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Question : 2

The main function of the heart is to pump __________________ and keep it moving in the blood vessels.
A. Blood	B. Lymph	C. Plasma	D. None of these .
Right Option : A
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Question : 3

Which of the following are correct ? (a) Heart is the pumping organ of our respiratory system. (b) The heart is located, slightly towards the left, in the chest. It is a muscular organ roughly of the size of the closed fist of the person. (c) The heart is divided into two equal halves - left half and right half. Each half is further divided into two chambers which have a common opening between them. There are, thus, four chambers in all.
A. Only (a) and (b) is correct .		B. Only (b) and (c) is correct .
C. Only (a) and (c) is correct .		D. All of these .
Right Option : B
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