Human Heart









The heart is one of the most important organs of human body. It is 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."

Heart of human

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 continuously, 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.





Position OF Human 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 the 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, 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.





How many Chambers in human heart ?

Human heart consist of 4 Chambers two ventricles and two auricles.

Left side has one auricle and one ventricle where as right side also has one auricle and ventricle . Left side pumps oxygenated blood and right side pumps deoxygenated blood.







Mediastinum It is the space between the two lungs, ie. the central subdivision of thoracic cavity. It extends from the sternum in front. the vertebral column behind and contains all the thoracic viscera except lungs, it is ranked on either side by the right and left pulmonary cavities, which house the lungs.











STRUCTURE OF HEART



The human heart is a muscular 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 weak 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.

(how much does a human heart weigh 7 pounds) An average adult heart is about 12 cm. Its weight varies in males from 280-340 g (average 300 g) and in females from 230-280 g (average 250 g). Weight of the heart is said to be about 0.45% of body weight in males and 0.40% in females. The heart is enclosed in a fibrous sac known as the pericardium and is surrounded by the lungs. The pericardium is made up of 2 layers , parietal and visceral pericardium. In between the two layers, a space called pericardial cavity is present which is filled o f heart with a pericardial fluid. The pericardium protects the heart from shocks and mechanical injuries and also allows free movements of heart.





Embryonic origin of heart The mammalian heart is derived from embryonic mesoderm that differentiates after gastrulation into mesothelium, endothelium, vessels develop from endothelium. Myocardium develops into heart muscle. and myocardium. Mesothelial pericardium forms the inner lining of the heart. The outer lining of the heart, lymphatic and blood vessels develops from endothelium. Myocardium develops into heart.