13.Give detailed structure and functioning of
human heart with labelled diagram.                                              (5)


The structure of the human heart
The heart consists of three layers:

Pericardium – is like a sheet that wraps outMyocardium – is the heart muscle, responsible for promoting blood through the body by contraction.Endocardium – it is a thin layer that covers the inside.

Within the heart are four chambers: two atria located at the top (right atrium and left atrium)

2 ventricles located at the bottom (left ventricle and right ventricle) there are also 4 valves – 2 atria ventricular valve, the tricuspid valve separates the right atrium from the right ventricle and the left atrium is separated from left ventricle by mitral valve. The other 2 are arterial ventricle, the right ventricle is separated from the pulmonary artery by pulmonary valve and aortic valve separates the left ventricle from the aorta.


The heart is the muscle that pumps oxygen-rich blood and nutrients to the body’s tissues through the blood vessels.

The heart keeps the blood moving in the body unidirectional, it is a closed circuit, and nothing is lost. The atria receive blood returning to the heart, the ventricles pump blood out of the heart.

The arteries carry oxygenated blood from the heart to the body tissues. Nutrients in tissues extracted and returned through the veins. Veins carry blood back to the heart.

The heart’s electrical system controls the rate of the heartbeat.

The heart is the hardest working muscle in the human body. The heart beats about 115,000 times a day, with an average rate of 80 times per minute, i.e. about 42 million times a year. For a normal lifetime, the human heart will beat more than 3,000 million times – pumping an amount of blood about one million barrels. Even when at rest, the heart continuously works hard.

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