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Explain the structure of mammalian heart with a neat labelled diagram.

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The heart of Mammals is somewhat fist shaped, broader at the anterior end and triangular, narrow & pointed at the posterior end marked by an apex at its tip.

MAMMALIAN HEART (MAN) SECTIONAL VIEW

The heart is made up of cardiac muscle and protected on its outer side with a double membrane, the pericardium, with its pericardial fluid. Internally the heart is 4 chambered with a left half consisting of the left auricle (receiving chamber) followed by the left ventricle (pumping chamber) and the right half consists of the right auricle (receiving chamber) and the right ventricle (pumping chamber). The left half is separated completely from the right half with the auriculoven-tricular septum.

The auricles or atrium (the receiving chambers) of the heart are anterior in position followed by the ventricles which posterior in position. The walls of the auricles are thinner than the ventricles and the walls of the ventricles bear special papillary muscles and tribaculae holding the valves present between the auricles and ventricles. The chambers are lined by simple squamous epithelium or endocardium. The auricles and ventricles are separated and guarded by valves allowing the flow of blood only in one direction due to their mode of arrangement.

The right auriculo-ventricular value is a tricuspid (3 flapped) valve opening towards the right ventricle and that between the left auricle and ventricle is the Bicuspid (2 flapped) or mitral valve opening towards the left ventricle.

The left side of the heart receives oxygenated blood through a set of blood vessels and pumps blood through a set of blood vessels towards the body. The right side of the heart receives impure (deoxygenated) blood from the body (cells) and pumps blood to lungs for purification through another set of blood vessels.

They are as follows;

(i) Superior and inferior vena cava:

Bring blood collected (deoxygenated) from various (upper NS and lower) parts of the body into the right auricle.

(ii) Pulmonary artery and its branches:

The pulmonary artery carries deoxygenated blood pumped by the right ventricle to the lungs for purification of blood in terms of respiratory gases (removal CO2 & addition of O2) channelised to left & right lobes of the lung with the help of its branches. The pulmonary artery is guarded by semilunar valves.

(iii) The pulmonary veins:

Collect the purified blood from the left & right lobes of the lung and carry it into the left auricle.

(iv) Aorta:

It is the largest vessel of the heart guarded by semilunar valves. It transports blood (oxygenated) pumped by the left ventricle (received from left auricle) into the body through its branches (to the upper and lower parts of the body).

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