Structure of human heart and Working of the heart

Human heart

                      The heart is conical, hollow muscular organ, situated in the thoratic cavity between the lungs. It is covered by a double walled protective membarne called pericardium.

                The heart consists of four chambers. Upper two chambers are called auricles and lower two chambers are called ventricles. The chambers are divided by partitions called septa. Auricles open into ventricles through openings which are guarded by values.

              Four pulmonary venis open into the left auricle. The superior and inferior vena cava which collect deoxygenated blood from various parts of the body open into the right auricle. The aorta arises from the left ventricle. It carries oxygenated blood to various parts of the body. Pulmonary artery arises from the right ventricle. It carries deoxygenated blood to the lungs.

Valves 

          The opening between the right auricle and right ventricle is guarded by tricuspid valve. Similarly, the opening between the left auricle and left ventricle is guarded by bicuspid valve or mitral valve. These valves allow the blood to flow in one direction. The opening of pulmonary artery into the right ventricle is guarded by semilunar valve. In the same way, the opening of aorta into the left ventricle is guarded by semilunar valve.

Working of human heart

                       Heart is the pumping organ, which pumps the blood to various parts of the body. Left auricle relaxes and receive the oxygenated blood. At the same time right auricle receives the deoxygenated blood. Then auricles contract and blood enters into their respective ventricles. Ventricles then contract and the blood from the ventricles enter into their respective blood vessels. Blood flows from left ventricle into aorta and from right ventricle into pulmonary artery. The contraction of the heart is called systole. The relaxation of the heart is called diastole.

                 These are three types of blood vessels. They are the following: Arteries, Veins and Capillaries.

                   The arteries carry blood from the heart to the various parts of the body. Arteries are thick walled and are placed deep inside the body. They divide to form smaller branches called arterioles.

                   The arterioles divide and subdivide to from the capillaries, which reunite to form the vein. The veins are thin walled. They are placed superficially. They carry blood from the different parts of the body to the heart.