Internal structure of heart class 12

Internally, the heart is divided into four chambers: • Two upper chambers known as atria: right atrium (RA) and left atrium (LA) ; • Two lower chambers called ventricles: right vetricle (RV) and left ventricle (LV). Functionally, the heart consists of two pumps (right and left), each consisting of an atrium and a ventricle separated by an atrioventricular valve. • The right pump (consisting of RA and RV) receives deoxygenated blood and pumps it into the pulmonary circulation). • The left pump (LA and LV) receives oxygenated blood from the lungs and sends it throughout the whole body (via the systemic circulation). The atria have relatively thin walls and they receive blood, while the ventricles with relatively thick walls pump blood out of the heart. The heart chambers are separated from each other by muscular walls known as septa (singular: septum). They include the following: • Interatrial septum - between atria; • Interventricular septum - between ventricles; • Atrioventricular septum - between atria and ventricles.

The human heart In all vertebrates including human beings, there is a single heart which acts as a pumping organ of blood vascular system. It receives and pumps blood from and to different organs of the body. For this purpose, it undergoes spontaneous, rhythmical and ceaseless contractions (beats) throughout the life. • Appearance and position: • Is a hollow, muscular organ (made up of involuntary cardiac muscles), roughly of the size of one’s fist (12×9 cm) • Average weight is about 300gm in males and 250gm in females • Is reddish-brown in color and somewhat conical in shape • Located almost in the middle of the thoracic cavity close to its front wall and between the lungs. Its broad base faces upward and backward whereas the narrow apex is directed downward, forward and slightly to the left. • Protective covering: • The heart is enclosed in a tough, two-layered sac, the pericardium, comprising inner visceral pericardium attached to the heart and the outer parietal pericardium. • The two layers have a potential space or cavity in between them, the pericardial cavity which consists of about 50 ml of pericardial fluid. • This fluid keeps the heart moist, allows its free movement and reduces the friction between the heart wall and the surrounding tissues when the heart beats. • The pericardium protects the heart from mechanical injury and checks its overstretching and overfilling with blood. • External structure: • The smaller upper chambers, auricles (atria) are demarcated ...

Hint: Heart is the four chambered organs present in the chest region and it is surrounded by the membrane called pericardial membrane. The main function of the heart is to pump the blood and transport it to all parts of the body. Complete answer: The mass of the heart is two third at the center. The layer of the pericardial membrane covering the heart is divided into three types as epicardium, myocardium and endocardium. Epicardium is the outer layer; myocardium is the middle layer and the endocardium is the inner layer covering the heart. Chambers of the heart: The heart is of four chambers as right atrium, right ventricle, left atrium and left ventricle. The atria are thin walled chambers that transport blood to all the parts of the body where the veins are of thick-walled membrane and receive blood from all the parts of the body. This thickness of the heart varies due to the width of the myocardium present. Right chambers receive deoxygenated blood and left chambers receive oxygenated blood. These chambers have valves between them to maintain the flow of blood in one direction. The valves between the right auricle and ventricle are called tricuspid valves. And between the left auricle and ventricle is a bicuspid valve. Valves between the pulmonary trunk and right ventricle are semilunar valves and between the left ventricle and aorta is a semilunar valve.