Human heart

 The heart is one of the most important organs of human body. It is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek word kardia, for "heart". The heart pumps the blood, which carries all the vital materials that help in various body functions. For example, the brain requires oxygen and glucose, which, if not received continously, will cause it to loose consciousness. Muscles need oxygen, glucose and amino acids, as well as the proper ratio of sodium, calcium and potassium salts in order to contract normally. The glands need sufficient supply of raw materials from which they manufacture the specific secretions. If the heart ever ceases to pump blood, the body begins to shut down and after a very short period of time, death occurs. All vertebrates including humans have a single heart.

Location of heart-:

In the human body, the heart is usually situated in the middle of the thorax with the largest part of the heart slightly offset to the left (although sometimes it is on right, underneath the breastbone). The heart is usually felt to be on the left side because the ventricle of left heart is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies more of the left hemithorax.

The heart is located in the mediastinum which is the space between two lungs, i.e., the central subdivision of the thoracic cavity. The heart apex is the blunt point situated in an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted. It is located posterior to the 5th intercostal space just median of the left mid-clavicular line

Structure of heart-:
The human heart is a mucular organ of a somewhat conical or pyramidal form with upper broad part, the base and lower narrow, the apex. The apex is slightly directed to the left.

The heart has actually two separate pumps: a right one that pumps blood through the lungs and a left one that pumps blood through the peripheral organs. In turn, each of these is a pulsatile two-chambered part composed of an atrium and a ventricle. Each atrium is a week primer pump for the ventricle, helping to move blood into the ventricle. The ventricles then supply the main pumping force that propels the blood to whole body.

An average adult heart is about 12cm in length, 9 cm in width and 6cm in thickness. Its weight varies in males from 280-340g (average 300g) and in females from 230-280g ( average 250g). Weight of the heart is said to be about 0.45% of body weight in males and 0.40% in females.

The heart in enclosed in a fibrous sac known as the pericardium and is surrounded by the lungs. The pericardium is made up of two layers: parietal and visceral pricardium. In between these two layers, a space called pericardial cavity is present which is filled with a pericardial fluid. The pericardium protects the heart from shocks amd mechanical injuries amd also allows free movements of heart.

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