Question

1. Briefly discuss the layers, chambers, valves, vasculature, and the conduction system of the heart.

Answer 1

The Heart:

The heart is a conical hollow muscular organ situated in the middle mediastenum.It is enclosed within the pericardium.

•Layers:

The heart consists of three layers outer epicardium,middle myocardium and inner endocardium.

• Chambers:

The human heart has four chambers.These are the right and left atria and the right and left ventricles.The atria lie above and behind the ventricles.The atria are separated from each other by interatrial groove.The ventricles are separated from each other by interventricular groove.Valves prevent the backflow of blood and separate the atria from ventricle and the ventricle from the pulmonary artery or aorta.

•Valves:

The valves of heart maintain the unidirectional flow of blood and prevent its regurgitation in the opposite direction.

There are two pairs of valves in the heart,a pair of atrioventricular valves and a pair of semilunar valves.

Left atrioventricular valve is called Bicuspid valve and the right atrioventricular valve is called Tricuspid valve.

The aortic and pulmonary valves are called semilunar valves.Each valve has three cups.These are present between ventricles of the heart and the pulmonary artery and aorta.

•Vasculature:

The heart is supplied by two coronary arteries arising from ascending aorta.Both arteries run in the coronary sulcus.

Right coronary artery has large marginal and posterior interventricular branches and other small branches like right atrial,right ventricular,conus,nodal and infundibular,terminal.

Left coronary artery has large anterior interventricular branch and branches to diaphragmatic surface of the left ventricle, including a large diagonal branch,and other small branches like left atrial, pulmonary,terminal.

The veins of the heart are great cardiac vein,middle cardiac vein,right marginal vein, posterior vein of the left ventricle, oblique vein of left atrium,anterior cardiac veins,and venae cardis minimi.

•Conduction system: It is made of myocardium that is specialized for initiation and conduction of the cardiac impulse.It has the following parts:

*Sinuatrial node (SA node) known as pacemaker of heart.It generates impulses.The impulse travels through the atrial wall to reach the AV node.

*Atrioventricular node (AV node) is smaller than the SA node and is present above the opening of the coronary sinus.

*AV bundle of his is the muscular contnection between atrial and ventricular musculature.It divides into right and left branches.

*The right and left branches divide into purkinje fibres which forms a subendocardial plexus.