Blood Vessels

Question 1

What is an artery?

Answer 1

Carries blood away from the heart and into the arterioles.

Question 2

What is an arteriole?

Answer 2

Smaller than arteries and they connect to the capillaries.

Question 3

What is a capillary?

Answer 3

Connects the arterioles to the veins.

Question 4

What is a vein?

Answer 4

Carries blood back into the heart.

Question 5

Describe the muscle layer of an artery.

Answer 5

The muscle layer of the arteries is thicker than veins so that constriction and dilation can occur to control the volume of blood.

Question 6

Describe the muscle layer of an arteriole.

Answer 6

The muscle layer of the arterioles is thicker than in the arteries to help restrict blood flow to the capillaries.

Question 7

Describe the muscle layer of a vein.

Answer 7

The muscle layer of the veins is relatively thin so it cannot control the flow of blood.

Question 8

Describe the muscle layer of a capillary.

Answer 8

Capillaries have no muscle layer.

Question 9

Describe the elastic layer of an artery.

Answer 9

The elastic layer of the arteries is thicker than veins to help maintain blood pressure. The walls can stretch and recoil in response to the heart beat.

Question 10

Describe the elastic layer of an arteriole.

Answer 10

The elastic layer of an arteriole is thinner than in the arteries as the pressure is lower.

Question 11

Describe the elastic layer of a vein.

Answer 11

The elastic layer of the veins is relatively thin as the pressure is much lower.

Question 12

Describe the elastic layer of a capillary.

Answer 12

No elastic layer in capillaries.

Question 13

Describe the wall thickness of an artery.

Answer 13

The wall thickness of the arteries is thicker than that of the veins to help prevent the vessels from bursting due to the high pressure.

Question 14

Describe the wall thickness of an arteriole.

Answer 14

The arterioles wall thickness is thinner as pressure is slightly lower.

Question 15

Describe the wall thickness of a vein.

Answer 15

The wall thickness of the veins is thin as the pressure is much lower so there is a low risk of bursting. The thinness means the vessels are easily flattened, which helps the flow of blood up to the heart.

Question 16

Describe the wall thickness of a capillary.

Answer 16

Capillaries have a one cell thick wall. This provides a short diffusion distance for exchanging materials between the blood and cells.

Question 17

What do veins have that the other blood vessels don’t?

Answer 17

Valves

Question 18

Describe the lumen of a vein.

Answer 18

The lumen of a vein is an irregular shape and it is much bigger than the arteries lumen.

Question 19

Describe the lumen of an artery.

Answer 19

The artery’s lumen is much smaller than the vein.

Question 20

Why is the lumen of a vein bigger than that of an artery?

Answer 20

This is due to the differences in the thickness of the wall.

Question 21

Why do capillaries have a narrow diameter?

Answer 21

To slow blood flow.

Question 22

What effect does it have when a red blood cell can only just fit in the diameter of the lumen of a capillary?

Answer 22

This slows the blood flow so there is more time for diffusion.

Question 23

Describe 3 adaptations of a vein.

Answer 23

• Wider lumen than arteries → less resistance to blood flow
• Very little elastic and muscle tissue → blood pressure lower
• Valves → prevent backflow of blood

Question 24

Describe 4 adaptations of a capillary.

Answer 24

• The wall is a thin (one cell) layer of endothelial cells -> reduces diffusion distance.
• Capillary bed -> large network of branched capillaries -> Increases surface area for diffusion.
• Small diameter / narrow lumen -> Reduces blood flow rate so more time for diffusion
• Pores in walls between cells -> Allow larger substances through

Question 25

What is the function of a capillary?

Answer 25

Allows efficient exchange of substances between blood and tissue fluid (exchange surface)

Question 26

What is the function of the arterioles?

Answer 26

Directs blood to different capillaries / tissues.

Question 27

Describe 2 adaptations of the arterioles.

Answer 27

Thicker smooth muscle layer than arteries - Contracts → narrows lumen (vasoconstriction) → reduces blood flow to capillaries - Relaxes → widens lumen (vasodilation) → increases blood flow to capillaries Thinner elastic layer → pressure surges are lower (as further from heart / ventricles)

Question 28

Describe 5 adaptations of the arteries.

Answer 28

- Narrow lumen - maintains high pressure. - Smooth/folded endothelium - reduces friction. - Thick wall - withstands high pressure and prevents bursting. - Thick smooth muscle tissue - Can contract and withstand pressure. - Thick elastic tissue - Can stretch as ventricles contract and recoil as ventricles relax, to maintain high pressure.