1. 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. Leucocytes are called soldiers of our body.
5. Valves are present in veins but not in arteries.
Answers
Answer:
The lower chambers are the right and left ventricles, which receive blood from the atria above. Their muscular walls are thicker than the atria because they have to pump blood out of the heart. Although the left and right ventricle are similar in structure,The white blood cells or leukocytes help provide immunity by destroying or killing foreign pathogens and antigen and thereby provide protection from diseases and infections. They are therefore called the soldiers of our body. the walls of the left ventricle are thicker and stronger.
The auricles and ventricles are guarded by valves because these valves control the flow of blood and also see that the blood does not flow back. They control the flow of blood in one direction.
Arteries and arterioles have relatively thick muscular walls because blood pressure in them is high and because they must adjust their diameter to maintain blood pressure and to control blood flow.
Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.
Answer:
(1) The lower chambers are the right and left ventricles, which receive blood from the atria above. Their muscular walls are thicker than the atria because they have to pump blood out of the heart.
(2) The auricles and ventricles on each side of the heart communicate with each other through openings.
(3) Arteries and arterioles have relatively thick muscular walls because blood pressure in them is high and because they must adjust their diameter to maintain blood pressure and to control blood flow.
(4) The white blood cells or leukocytes help provide immunity by destroying or killing foreign pathogens and antigen and thereby provide protection from diseases and infections. They are therefore called the soldiers of our body.
(5) Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.