HEART

The heart is a conical hollow muscular organ.

Position
 It is situated in the middle mediastinum.

Structure of the heart
*Anterior or sternocostal surface
*Inferior or diaphragmatic surface
*Posterior surface or base

  Borders of the heart
 1. Right border
 2. Inferior border, at the left extremity of which  is the apex.
 3. Left border, which separates the anterior and left surfaces of the heart.

Chambers of the heart
Mention the different chambers of the heart.

The heart has four chambers
right and left atria, and right and left ventricles. The tissue separating the two atria is the interatrial septum, and the separating the two ventricles is the interventricular septum.

Right atrium
It is the right upper chamber of the heart. It receives venous blood from the whole body through three vessels :
1. superior vena cava
2. Inferior vena cava
3. Coronary sinus, which returns blood from the walls of the heart itself.


Right ventricle
The right ventricle is a triangular chamber which receives blood from the right atrium and pumps it to the lungs through the pulmonary trunk and pulmonary trunk and pulmonary arteries.

Left atrium
The left atrium is a quadrangular chamber situated posteriorly. It receives oxygenated blood from the lungs through four pulmonary veins, and pumps it to the left ventricle through left atrioventricular orifice (mitral orifice).

Valves of the heart
Types of valves of the heart
For maintaining unidirectional blood flow through the heart, it contains four valves in its orifice :
1. tricuspid
2. pulmonary
3. mitral
4. aortic