Describe The Anatomy Of the Heart
Description:
A human heart is a triangular and muscular organ located in the thoracic cavity between the lungs. The human heart is about 12 cm in length and 250 gm in weight. It is larger in males than in females. It is enclosed and protected in a double-walled pericardium. The outer is the parietal pericardium and the inner is the visceral pericardium. The cavity between two pericardial membranes is filled with pericardial fluid that protects the heart from shocks, and mechanical injury and also allows free movements of the heart during a heartbeat.
The external structure of the heart
The human heart is a four-chambered organ, having two auricles and two ventricles. The right auricle and right ventricle are the chambers for the impure blood whereas the left auricle and left ventricle are for the pure blood. There is no mixing of impure and pure blood in the heart.
- Auricles: Auricles are thin-walled chambers. The left auricle is smaller than the right auricle. The left and right auricles are externally separated by a vertical inter-auricular groove. Similarly, the auricle and ventricle are extremely demarcated by an oblique groove called auriculo-ventricular sulci. Besides that, there are coronary sulcus and interventricular sulcus present.
The right auricle receives the venous(impure) blood from different parts of the body through openings-one superior vena cava, one inferior vena cava, and one coronary sinus. Similarly, the left auricle receives oxygenated (pure) blood from the lungs through openings of two pairs of pulmonary veins.
- Ventricles: Ventricles are thick-walled. The left ventricle is somewhat longer and about three times thicker than the right ventricle. The right ventricle receives impure blood from the right auricle, whereas the left ventricle receives pure blood from the left auricle. There is no mixing of pure and impure blood.
- Aorta And Pulmonary Trunk: An aorta arises from the left auricle. It has two parts- ascending and descending aorta. The ascending aorta gives off three aortic arches- Brachiocephalic left common carotid and left subclavian. Coronary arteries arise from the ascending aorta and supply blood to the heart. Aorta supplies pure blood throughout the body. The pulmonary trunk arises from the right ventricle. It divides into left and right pulmonary arteries that carry deoxygenated blood to the lungs.
The internal structure of the heart
The internal structure of the human heart has the following parts:
- Auricles:
- Ventricles:
- Bicuspid and Tricuspid valve: The auricles and ventricles are separated by the auriculo-ventricular septum. Each auricle opens into its corresponding ventricle through an auriculo-ventricular aperture. These apertures are guarded by flaps or valves which open only in the ventricle and prevent the back-flow of the blood. The left auriculo-ventricular aperture is guarded by a bicuspid valve or mitral valve. Similarly, the right auriculo-ventricular aperture is also guarded by a tricuspid valve. These valves are attached by fibrous cords called chordae tendineae with papillary muscles of the ventricular wall. Papillary muscles are the extensions of the ventricle wall. Its main function is to hold the flaps of valves and thus not allow them to enter the auricles during powerful ventricular contraction.
- Semilunar valves: These valves are located at the base of openings of the aorta and pulmonary trunk. Each valve is made up of three flaps half-moon shaped, attached to the inside of the arterial wall. These valves prevent the blood from returning back to the ventricles once forced out.
