Short notes on the structure of human heart

The heart is covered by a wall called pericardium which is made up of three layers. These are the epicardium, the myocardium and the endocar­dium. The epicardium is a serious membrane and is the outer most layers. This secrets a serious fluid into the space between the visceral and the parietal pericardium. This fluid called the pericardialfluid allows smooth movement when the heart beats. It has been estimated that there will be normally about 15 ml of the pericardial fluid.

The myocardium is the intermediate layer. It is composed of specialised muscle tissues called the cardiac muscles. These muscles are striated fi­bres. The myocardium is thin in the auricles but thick in the ventricles specially so in the left ventricle.

The endocardium is the inner most layer. This is a thin membranous struc­ture in contact with the blood. It is composed of flattened endothelial cells. The endocardium is thicker in the auricles than in the ventricles. Internally the heart is composed of 4 chambers namely


1. Right auricle (atrium)

2. Left auricle (atrium)

3. Right ventricle and

4. Left ventricle


There are two auricles – the right and the left. These are separated by a thin interauricular septum. The ventricles are also two in numbers and they are separated by the interventricular septum. The right auricles open into the right ventricle by the right auriclo ventricular openings guarded by a tricuspid valve having three flaps.

The left auricle opens into the left ventricle by left auriclo ventricular aperture guarded a bicuspid valve Jiaving two flaps. This valve is also called the mitral valve. The right auricle receives venous blood through superior and inferior vena cave. The left auricle receives oxygenated blood through the pulmonary vein returned from the lungs.