Structure of Heart

Topics: Heart, Right ventricle, Blood Pages: 3 (957 words) Published: April 26, 2013


Position, Shape and Size of the Heart:
The human heart is located between the lungs in the thoracic cavity (i.e. it is not situated on the left side of the chest). The heart is a hollow, fibro-muscular organ and is somewhat conical in shape. It is about the size of one’s fist, measures about 12 cm in length and 9 cm in breadth. Its weight is about 300 g in an adult. The heart is enclosed in pericardium (a double- layered membranous sac). It protects the heart from mechanical injury. The space between two pericardial membranes is the pericardial space, which is filled with the pericardial fluid. The pericardial fluid keeps the heart moist and reduces friction between the heart wall and the surrounding tissues when the heart beats. Human heart is made of cardiac muscles or myocardia which contract rhythmically by self generated impulse.

The human heart has a mass of between 250 and 350 grams and is about the size of a large fist.[12] It is enclosed in a double-walled protective sac called the pericardium. The superficial part of this sac is called the parietal pericardium. The inner pericardium layer is called the visceral pericardium. Together they are usually called the serous pericardium because they contain the pericardial fluid. Outside the parietal pericardium there is a fibrous layer which depends from the mediastinal fascia and is called the fibrous pericardium.[13] The pericardium sac protects the heart, anchors its surrounding structures, but has no effect over the heart function in normal individuals.[14] The double membrane of pericardium contains the pericardial fluid which provides a smooth lubricated sliding surface within which the heart organ can move in response to its own contractions and to movement of adjacent structures such as the diaphragm and lungs.[15]

At 21 days after conception, the human heart begins beating at 70 to 80 beats...
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