Examville.com – Quick Review of Anatomy – Structure of Human Heart

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STRUCTURE OF HUMAN HEART
It is a blunt conical organ of about 12 cm long and 9 cm broad, Its narrow apex is pointed downward and to the left. Heart is enclosed in a double walled sac called Pericardium outer membrane is parietal pericardial membrane (fibrous) and inner one is visceral pericardial membrane (serous). In between the two layers is a fluid-filled space, the fluid is called pericardial fluid & it prevents any friction between the heart walls and the surrounding tissues, protection from shock and mechanical injury. Heart-wall consists of three layers–epicardium (outermost), Myocardium (middle one) and endocardium (inner most). Among these three layers, myocardium consists of cardiac muscles, resembling the striated muscles structurally and smooth muscles functionally because of involuntary muscle. The human heart consists of four chambers two auricles (atria) and two ventricles. The auricles are located at the broader end and the ventricles are towards the posterior narrow end. There is an external transverse groove between the auricles and ventricles, it is called coronary sulcus.

Internally, the two (right and left) auricles are separated by an inter atrial septum. It has an oval depression called fossa ovalis, which is the remnant of foramen ovale of foetal heart. The two ventricles are separated by inter-ventricular septum. The atria and ventricles are separated by auriculo-ventricular septum (Av septum). It has an opening between the right auricle and right ventricle, guarded by tricuspid valve.

The opening in the A-v septum between the left auricle and left ventricle is guarded by biscuspid or mitral valves. The pointed ends of the flaps of A.V. valve are attached to the ventricular wall by chordae tendinae. The right auricle receives inferior and superior vena cava and the left auricle receives two pairs of pulmonary veins. The two major arteries leaving the heart are pulmonary artery (from right ventricle) and aorta from left ventricles) their openings are guarded by semilunar valves. The wall of the heart is made of cardiac muscle fibres which branch & connect with one another forming a network, this facilitates quick conduction of the cardiac impulse. Coronary arteries & vein supply blood to the cardiac muscles.