Aarti Gupta
Ans1).Arteries:--
1.Arteries carry oxygenated blood,away from the heart except pulmonary artery.
2..These are mostly deeply situated in the body.
3.These are thick-walled, highly muscular.
4.These posses narrow lumen.
5.Valves are absent.
6.These are reddish in color.
7.Blood in arteries moves with pressure.
Veins:--
1.Veins carry deoxygenated blood,towards the heart except pulmonary veins.
2.These are superficial and deep in location.
3.These are thin-walled.
4.These posses wide lumen.
5.Valves are present which provide unidirectional flow of blood.
6.These are bluish in color.
7.Blood in veins moves under very low pressure.
Ans2) . Blood goes through the heart twice during each cycle in vertebrates like animals having three-chambered heart like frogs,lizards and those having four-chambered heart like mammals and birds.Such circulation is called as double circulation which can be understand as that there are two circuits for blood passing through the heart--
1.Pulmonary Circulation– Deoxygenated blood is pumped from the heart to the lungs,and oxygenated blood returns to the heart from the lungs.
2. Systematic Circulation-- Oxygenated blood is pumped from the heart to the entire body including all the organs and then the deoxgenated blood returns to the heart as much of the oxygen has been supplied to the tissues.
Thus during one complete cycle of flow through the whole body,blood in a double circulatory system passes through the heart twice.
