Human Heart

Human Heart Anatomy and How they Work

Heart The human heart is a specialized; four-chambered that maintains BLOOD flow in the hearth circulatory system. Located in the thorax, it lies left of the body’s mid line, above and in contact with the diaphragm. It is situated immediately behind the breastbone, or sternum, and between the lungs, with its apex tilted to the left. At rest, the hearts pumps about 59 cc (2 oz) of blood per beat and 5 l (5 qt) per minute, compared to120-220 cc (4-7.3 oz) per beat and 20-30 l (21-32 qt) per minute during exercise. The adult human heart is about the size of a first and weighs about 250-350 gm (9 oz).

Human heart

Blood supplies food and oxygen to the cells of the body for their life needs and removes the waste products of their chemical processes. It also helps to maintain a consistent body temperature, circulate hormones, and fight infections. Research indicates that the heart it self produces a hormone like chemical. Brain cells are dependent on a constant oxygen supply, so death ensues shortly if a heart attack halts circulation to the brain. Such attacks are the number-one cause of death in the United States .

Structure and Function of the Human Heart

The heart’s wall has three parts. Muscle tissue, or myocardium, is the middle layer. The inner layer, or endocardium, that lines the inside of the heart muscle consists of a thin layer of endothelial tissue overlying a thin layer of vascularized connective tissue.

The outside of the heart, the epicardium, is in intimate contact with the pericardium; this serous membrane is a closed sac covering the heart muscle’s outside wall. Within the sac, a small amount of fluid reduces the friction between the two layers of tissue. In addition to muscular and connective tissue, the heart muscle contains varying amounts of fatty tissue, especially on the outside. Both anatomically and functionally, the heart is divided into a left and a right half by the cardiac septum. Each half contains two separate spaces: the atrium (pl. atria), or auricle, and the ventricle.

The upper reservoirs, or collecting chambers, are the thin-walled atria, and the lower pumping chambers are the thick-walled ventricles. The total thickness of the ventricular walls is about three times that of the atria; the wall of the hearts left half is approximately twice as thick as that of the right half. The thickness of the heart muscle varies from 2 to about 20 mm (0.1 to 0.8 in). This thickness is correlated with the maximum pressure that can be attained in each chamber.