Blood Vessels

Question 1

Describe the structure of the inner endothelium layer

Answer 1

This layer is smooth, reducing friction. This reduces resistance, making it easier for blood to flow.

Question 2

Describe the structure of the smooth muscle

Answer 2

the muscle can cause the vessel to constrict (narrow) and dilate (widen) to control blood flow

Question 3

Describe the structure of the elastic layer

Answer 3

The elastic layer stretches and recoils to maintain pressure

Question 4

Describe the structure of the collagen outer layer

Answer 4

Provides protection

Question 5

Contrast the structure of an artery and a vein

Answer 5

• Arteries have a thicker muscle layer than veins
• Arteries have a thicker elastic layer than veins
• Veins have a wider lumen than arteries
• Veins have valves whereas arteries do not

Question 6

Contrast the structure of an arteriole and an artery

Answer 6

• Arterioles have a relatively thicker muscle layer compared to arteries.
• Arteries have a relatively thicker elastic layer compared to arterioles.

Question 7

Which layer is present in capillaries

Answer 7

Endothelium

Question 8

Why is only one layer present in capillaries

Answer 8

Capillaries are the sites of exchange therefore need a shorter diffusion distance to increase the rate of diffusion

Question 9

Why are capillaries considered to be a tissue whereas arteries are an organ

Answer 9

Capillaries are only made from one type of cell, whereas arteries are made from several types and therefore several tissues

Question 10

Why do arteries have a thicker elastic layer than other types of vessel

Answer 10

The recoil smooths out the pressure, helping to maintain a constant pressure at all times

Question 11

Why do arteries and arterioles have a thicker muscle layer than other vessels

Question 12

Why don’t veins need a thick elastic layer

Answer 12

Veins are further from the ventricles

Question 13

Why do veins need valves but arteries don’t

Answer 13

Back flow will more likely occur in veins because blood is at a lower pressure

Question 14

Why don’t veins need a thick muscle layer

Answer 14

There’s no need to regulate flow, because we want all the blood to go back to the heart

Question 15

Why do veins need a relatively thinner wall

Answer 15

• Low pressure in veins
• A thicker wall would mean that the muscle pump wouldn’t sufficiently squeeze the vessels to create pressure

Question 16

Why do veins need a larger lumen

Answer 16

• Resistance is inversely proportional to vessel diameter
• As diameter increases, resistance decreases so blood flow in veins increases

Question 17

Why do capillaries have an endothelium that is only one cell thick

Answer 17

Shorter diffusion distance

Question 18

Why are capillaries numerous and highly branched

Answer 18

Increases SA

Question 19

Why do capillaries have a narrow lumen?

Answer 19

• Resistance increases
• Blood flow slows down

Question 20

Why do some capillaries have spaces between the cells in the endothelium (fenestrations)

Answer 20

Allows things out of the capillaries into the tissues e.g. WBCS