The heart and the network of blood vessel constitute cardia vascular system. It consist of heart, arteries and veins, pulmonary and systemic circulation, various valves, ad conduction system like SA and SV nodes punkinjec fibres which maintains heart contractions.
Heart is a hollow muscular organ located in the space called mediastinum, between the lungs in the thoracic cavity. It weighs about ¼ kg and is of the size of one’s fist. It is located with its broad end base above and apex narrowed below.
Pericardium is a tough membrane, double layered fibroserous sac that covers the heart and protects it from overdistention. The tough outer layer is called pericardium and the inner layer is called visceral pericardium that closely adheres the heart. In between pericardial fluid is present that protects the heart from friction and helps free movement of heart.
Heart wall and its structure. The wall of the heart is made up of three layers of tissue from outside to inside. The external layer is the epicardium, the middle layer is thick endocardium and the inner most one isendocardium. Heart is divided into halves. Each half is further divided into upper auricle and lower ventricle. The vertically are atria (right and left) , while the lower chambers are ventricles. The Inter Ventricular and interatrial septum separates the two ventricles and two artia. The right half is concerned with pulmonary blood circulation while the left half of the heart is concerned with systemic blood circulation.
Right atrium receives the blood from the lower and upper parts of the body through inferior and superior vena cava respectively. When the atrium is full, it contracts and the blood flows into the relaxed right ventricle. When the ventricle is full it begins to contract allowing the blood to pass into lungs through pulmonary arteries. To prevent the blood flow back into atrium, the right atrio ventricular valve or tri cuspid valve closes.