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Question
What is circulatory system? Describe the circulatory system of humans.
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Solution
The system that transports nutrients in the body and collects waste materials for disposal is the circulatory system.
Circulatory system of humans
Humans have a closed circulatory system. Blood pumped by the heart always flows through a closed network of blood vessels.
Human circulatory system consists of blood, a muscular, four-chambered heart and a network of closed, branching blood vessels − veins, arteries and capillaries.
(i) Heart:
In human beings, the heart is a muscular organ. It is divided into four chambers – right auricle, right ventricle, left auricle, and left ventricle. The walls of these chambers are made up of a special muscle called myocardium, which contracts continuously and rhythmically to distribute blood to all the body cells.
(ii) Blood:
Blood is a red coloured connective tissue consisting of a fluid matrix, plasma, and consists of RBCs, WBCs and platelets. Blood carries other substances around the body, inside arteries, veins and capillaries. These include gases (oxygen and carbon dioxide), waste products (water and urea), hormones, enzymes and nutrients (glucose, amino acids, vitamins and minerals). Blood flows through the circulatory system.
(iii) Blood vessels:
Arteries are tough, elastic tubes that carry blood from the heart and supply it to various organs of the body. As the arteries move away from the heart (i.e., on reaching organs and tissues), they divide into smaller vessels. The smallest vessels called capillaries have very thin walls. Arteries are red in colour because they carry oxygenated blood.
Capillaries (in organs and tissues) join together to form veins. Veins collect blood from different organs and tissues. Veins are thin-walled as compared to arteries. This is because they bring back blood from the organs to the heart and blood is no longer under pressure. These veins carry deoxygenated blood into the heart.
Circulatory system of humans
Humans have a closed circulatory system. Blood pumped by the heart always flows through a closed network of blood vessels.
Human circulatory system consists of blood, a muscular, four-chambered heart and a network of closed, branching blood vessels − veins, arteries and capillaries.
(i) Heart:In human beings, the heart is a muscular organ. It is divided into four chambers – right auricle, right ventricle, left auricle, and left ventricle. The walls of these chambers are made up of a special muscle called myocardium, which contracts continuously and rhythmically to distribute blood to all the body cells.
(ii) Blood:
Blood is a red coloured connective tissue consisting of a fluid matrix, plasma, and consists of RBCs, WBCs and platelets. Blood carries other substances around the body, inside arteries, veins and capillaries. These include gases (oxygen and carbon dioxide), waste products (water and urea), hormones, enzymes and nutrients (glucose, amino acids, vitamins and minerals). Blood flows through the circulatory system.
(iii) Blood vessels:
Arteries are tough, elastic tubes that carry blood from the heart and supply it to various organs of the body. As the arteries move away from the heart (i.e., on reaching organs and tissues), they divide into smaller vessels. The smallest vessels called capillaries have very thin walls. Arteries are red in colour because they carry oxygenated blood.
Capillaries (in organs and tissues) join together to form veins. Veins collect blood from different organs and tissues. Veins are thin-walled as compared to arteries. This is because they bring back blood from the organs to the heart and blood is no longer under pressure. These veins carry deoxygenated blood into the heart.
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