Anatomically, the heart was nearly the size of a fist for a weight ranging from 250 to 350g. It lies within the mediastinum, extending from the 2nd to 5th coast intercostal space between the spine and sternum, surrounded by the lungs, its apex resting on the diaphragm.

I-The pericardium:

The outer core is called the pericardium, made of dense and strong, protecting the heart, then two layers, one parietal and other visceral, defining a virtual cavity, where the cells produce pericardial fluid in serous for lubrication.


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II-The myocardium.

This is the tunic “through” the heart, composed mainly of cardiac muscle cells, and has the capacity to contract. They are entangled in a network of elastic fibers of connective tissue, forming the cardiac fibrous skeleton, thicker in places to form rings of support around the perimeter of valves and points of emergence of the great vessels.

III-The endocardium.

Corresponds to the inner layer made of a squamous epithelium, lining the heart chambers and is continuous with the endothelium of large vessels.

IV-cavities and great vessels.

The heart has four chambers, two atria and two ventricles.

From the right atrium entering three veins: the superior vena cava blood of bringing the regions above the diaphragm, the vena cava, bringing blood to areas under the diaphragm, and the coronary sinus, reducing the blood used by the myocardium itself.

From the left atrium arrive four pulmonary veins (attention to the confusion, however, the pulmonary veins bring oxygenated blood, but should not be called pulmonary arteries, which they bring the vitiated blood to the lungs).

Circulatory level, there are the lesser circulation or pulmonary circulation and the systemic circulation or systemic circulation:

The right heart is the pump of the pulmonary circulation, the oxygen-poor blood enters through the right atrium, then descends into the right ventricle, which propels the blood into the pulmonary trunk, from which both pulmonary arteries which carry the blood to cells. Then he goes back through the pulmonary veins to reach the left heart.

The left heart is the pump from the systemic circulation: the oxygen-rich blood from the lungs enters the pulmonary veins by the left atrium, before being expelled by the ventricle into the aorta, from which all branches to the different systems. Then he goes back through the venous system via the vena cava, the right heart.

The V-valve system.

Like any pump, the heart can not ensure its effectiveness in the presence of anti-reflux system, a role held in by four heart valves, two atrio ventricular valves, the aortic valve and the pulmonary trunk.

Atrio ventricular valves are located at the junction between the atrium and ventricle. The atrioventricular valve right ventricle, tricuspid valve is called the left is called bicuspid. Thin White cords of collagen anchor the valves and thus allow the sealing of these, but also prevent a reversal of the valve in his headset.

The valve of the aorta and pulmonary trunk has a role to prevent reflux into the ventricles

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