Do you know that in a year your heart beats over 30 million times? This means in a lifespan of 80 years, it would be around 2.5 billion times. How does the heart make up its pace? What are the different parts of a heart? Let us have a brief discussion on the structure of the human heart and blood vessels.
The heart is a fist-sized muscular organ made up of cardiac muscles. Heart, blood and a network of arteries, veins, and other blood vessels make the cardiovascular system. The heart is the key structure of a circulatory system because it is the motor or pumping organ which helps in circulation of blood throughout the body as per requirement. For example, during exercise or other heavy works, it pumps more blood than during rest.
The heart is located in the thoracic cavity between the lungs and protected by a thick wall called pericardium. It is divided into four chambers namely- right and left atria and left and right ventricles. Atria are present on the top and ventricles are the chambers at the bottom. Interatrial septum is a thin wall which separates the right and left atria whereas two ventricles are divided the by interventricular septum. Valves are the fibrous tissues which ensure the unidirectional flow of blood in the heart. The valve present between the right atrium and ventricle is known as tricuspid valve and this prevents the backward flow of blood from the right ventricle the to right atrium. Mitral or bicuspid valve is the valve that separates the left atrium and ventricle.
Sino-atrial node (SA node) and atrioventricular node (AV node) are the two nodal tissues present in the human heart and it is mainly involved in helping the heart to produce its own action potential (impulses). This action potential results in the contraction of cardiac muscles (heart muscles) and causes the pumping of blood. Around 70-75 impulses per minute are made by SA nodes and maintain the rhythm of the heart beating. Thus SA nodes are called as pacemakers.
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