Tue May 01, 2012 By:

explain briefly about circulatory system in humans...!!

Expert Reply
Tue May 01, 2012

The main components of the human circulatory system are the heart, blood, blood vessels and lymphatic system. 


The human heart contains four chambers: two atria and two ventricles. Oxygen-poor blood enters the right atrium through a major vein called the vena cava. The blood passes through the tricuspid valve into the right ventricle. Next, the blood is pumped through the pulmonary artery to the lungs for gas exchange. Oxygen-rich blood returns to the left atrium via the pulmonary vein. The oxygen-rich blood flows through the bicuspid (mitral) valve into the left ventricle, from which it is pumped through a major artery, the aorta to different parts of the body.



Blood is the medium of transport in the body. The fluid portion of the blood, the plasma, is a straw-coloured liquid composed primarily of water. All the important nutrients, the hormones, and the clotting proteins as well as the waste products are transported in the plasma. Blood contains three types of blood cells i.e. red blood cells, white blood cells and platelets, which are suspended in the plasma.

Red blood cells transport respiratory gases throughout the body, white blood cells helps to defend body against diseases and foreign particles and platelets are essential for blood clotting.


Blood vessels:

The three important blood vessels are arteries, veins and capillaries.

Arteries are blood vessels that carry the oxygenated blood away from the heart.

Veins are the blood vessels that carry deoxygenated blood back to the heart.

Capillaries are the smallest blood vessels in the body. Their structure consists of just a single layer of endothelial cells. Water and other small-molecule substances can pass through this wall. Capillaries act as a link between arteries and veins. The exchange of blood and tissue takes place at the capillary bed.


Lymphatic system :

The lymphatic system is an extension of the circulatory system consisting of a fluid known as lymph, capillaries called lymphatic vessels, and structures called lymph nodes. Lymph is a watery fluid derived from plasma that has seeped out of the blood system capillaries and mingled with the cells. Rather than returning to the heart through the blood veins, this lymph enters a series of one-way lymphatic vessels that return the fluid to the circulatory system. Along the way, the ducts pass through hundreds of tiny, capsule-like bodies called lymph nodes.

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