Discuss the functional organization of mammalian circulatory system.

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It consists of the heart, blood vessels and blood.

The heart is a muscular organ that contracts rhythmically, pumping the blood through the circulatory system. Its wall consists of three tunics: endocardium (internal), myocardium (middle) and pericardium (external). The endocardium is a single layer of squamous cells. The myocardium is the thickest layer and consists of cardiac muscle cells arranged in layers. The pericardium is a membranous bag that surrounds the heart. The pericardial sac contains fluid that lubricates the heart and facilitates its movement.

The heartbeat is also called cardiac cycle. The left ventricle takes in a volume of blood from pulmonary veins and left atrium and ejects it into aorta. The right ventricle takes in a similar volume of blood from systemic veins and right atrium and ejects it into the pulmonary artery. Each heartbeat consists of a ventricular diastole (rest period) and a ventricular systole (contraction period).

Blood enters the heart by way of superior vena cava and inferior vena cava into the right atrium. The tricuspid valve releases it into the right ventricle which pumps it through the pulmonary valve and pulmonary artery into the lungs for oxygen and release of CO2. The pulmonary vein carries blood into the left atrium and the mitral valve feeds it to the left ventricle. Finally its pumped past the aortic valve and into the aorta and back into circulation. Dividing the two sides of the heart is the muscular septum. The point of the heart is called the apex.

Arteries are blood vessels that carry oxygen-rich blood from the heart (except pulmonary artery) to various body tissues. Their walls are thick and contain heavy muscular layer that can withstand the blood pressure produced by the heart. They branch into smaller tubes known as arterioles and capillaries.

Veins are blood vessels that return blood from throughout the body to the heart and then convey it to the lungs, where CO2 collected from the body and oxygen from the atmosphere are exchanged. Both arteries and veins have valves which prevent “back flow”.

Capillaries constitute the smallest blood vessels and they form a complex network of thin tubules that anastomose profusely and through whose walls the interchange between blood and tissues occur. Transfer of nutrients from blood to tissue, and waste products from tissue to blood takes place in capillaries. Capillaries are widely distributed in tissues

marto answered the question on April 16, 2019 at 09:05

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Discuss the functional organization of mammalian circulatory system.

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