Structure And Function Of Blood Vessels

Question 1

How do arteries and veins differ in function?

Answer 1

Artery’s transport high pressure blood away from the heat whereas, veins transport low pressure blood back to the heart.

Question 2

How are arteries and veins similar in structure?

Answer 2

1. Tough outer coat
2. Smooth muscle and elastic tissue
3. Inner single cell layer of smooth endothelium

Question 3

How do arteries and veins differ in structure?

Answer 3

1. Arteries have a narrow lumen, but veins have a wide lumen
2. Arteries are thicker than veins as they carry blood at higher pressures
3. Arteries contain more smooth and elastic tissue than veins
4. Not all arteries have valves but all veins do

Question 4

What is the importance of elastic tissues to arteries?

Answer 4

• arteries carry blood at high pressures away from the heart
• the aorta has a thick layer of elastic tissue and when the left ventricle contracts, the aorta wall stretches and when the left ventricle relaxes, the aorta wall recoils
• this helps to smooth out surges in blood flow and helps to maintain a relatively high blood pressure
• aorta contain a higher ratio of elastic fibres to smooth muscle fibres to withstand blood pressure and helps smooth blood flow

Question 5

What features do veins have that allow for low pressure blood to be returned back up to the heart?

Answer 5

1. Semi-lunar valves at intervals
   —> prevent back flow which ensures blood travels in one direction towards the heart
2. Contracting muscles in the legs and body
   —> these press on the veins and squeeze the blood along

Question 6

Describe the structure and function of arterioles.

Answer 6

• made up of the same 3 layers as arteries and have a higher proportion of smooth muscle compared to elastic fibres
• arterioles control the flow of blood to different tissues or organs by contraction or relaxation of smooth muscle in their wall

Question 7

What is vasodilation?

Answer 7

• the middle layer of smooth muscle relaxes causing the arterioles to widen
• increasing blood supply to the capillaries

Question 8

What is vasoconstriction?

Answer 8

• the middle layer of smooth muscle tissue contracts causing the arterioles to narrow
• this reduces the blood supply to capillaries

Question 9

Describe the structure of capillaries.

Answer 9

1. Walls are made of endothelium tissue which is one cell thick
   —> very short diffusion distance
2. Lumen is very narrow
   —> red blood cells travel slowly in single file giving more time for diffusion
3. Tissue cells are very close to capillaries
   —> short diffusion pathway
4. Large number of capillaries arranged in capillary beds
   —> large total surface area for faster diffusion