Give reasons for the following.
1. Ventricles have thicker walls than auricles.
2. Openings of auricles into ventricles are
guarded by valves.
3. Arteries have thick walls.
4. Valves are present in veins but not in arteries.
5. Persons of blood group O are universal
donors.
Answers
Explanation:
1 ventricle are thick because it has to pump blood from heart to various distant organs hence requires a get muscle contraction. The wall of ventricles have hence more muscles hence thick.
2 the valves present between the auricles and ventricles prevents the back flow of blood when the ventricle is contracted. The valves get closed during contraction and blood makes pressure on valves between the ventricle and aorta and pulmonary arteries. Hence the valves open and blood goes to lungs and other body organs.
3 Arteries have thick walls to help maintain the pressure of blood flow through out the body. Cause of the thick walls and narrow lumen the blood reaches ever part effectively with nutrients.
4 The pressure with which the ventricles pumps the blood is effective enough to reach all parts of body. But when the blood has to reach heart from body part there is no force which can push the blood till the heart. Hence the valves helps the bloods backflow and helps it to reach heart.
5 The blood has a pair of antibodies and antigens. But in O blood group antigens are absent from RBCs hence it can be given to any person with unknown origin while other Rh factor hold importance while blood transfer. Specifically O negative blood is transferred cause its Rh factor is also absent so it can help in blood transfusion