8.2 Blood Vessels

Question 1

what are the different components utilised in blood vessels

Answer 1

elastic fibres
smooth muscle
collagen

Question 2

elastic fibres

Answer 2

composed of elastin and can stretch and recoil providing vessels walls with flexibility.

Question 3

smooth muscle

Answer 3

contracts or relaxes which changes the size of the lumen

Question 4

collagen

Answer 4

provides structural support to maintain the shape and volume of the vessel

Question 5

arteries structure

Answer 5

Artery walls consist of 3 layers. Tunica externa/adventitia, tunica media and tunica intima.
Artery walls contain elastin fibres, smooth muscle and collagen.
Have a narrow lumen which helps to maintain a high blood pressure
A pulse is present in arteries

Question 6

tunica intima

Answer 6

made up of an endothelial layer, a layer of connective tissue and a layer of elastic fibres.
The endothelium is one cell thick and lines the lumen of all blood vessels.
It’s very smooth and reduces friction for free blood flow.

Question 7

tunica media

Answer 7

made up of smooth muscle cells and a thick layer of elastic tissue.
Arteries have a thick tunica media.
The layer of thick muscle cells strengthen the arteries the arteries so they can withstand high pressure, also enables them to contract and narrow the lumen for reduced blood flow.
The elastic tissue helps to maintain blood pressure in the arteries, it stretches and recoils to even out any fluctuations in pressure.

Question 8

tunica adventitia

Answer 8

covers the exterior of the artery and is mostly made up of collagen.
Collagen is a strong protein protecting blood vessels from damage by over-stretching.

Question 9

arteries function

Answer 9

Arteries transport blood away from the heart (usually at high pressure) to tissues

Carry oxygenated blood except from pulmonary artery which carries deoxygenated blood from the heart to the lungs

Question 10

arteries adaptations

Answer 10

Endothelium is one cell thick and lines the lumen of all blood vessels, it’s very smooth and reduces friction for free blood flow

Thick tunica media strengthens arteries so they can withstand high pressure.

Collagen is strong so protects blood vessel from damage by over stretching

Narrow lumen maintains high blood pressure

Elastin fibres enable arteries to withstand the force of blood pumped out of the heart and stretch (within limits maintained by collagen) to take the larger blood volume. In between contractions of the heart, the elastic fibres recoil and return to their original length

Question 11

arterioles structure

Answer 11

Unlike arteries, arterioles have a lower proportion of elastic fibres and a large number of muscle cells.
Presence of muscle cells allows them to contract and close their lumen to stop and regulate blood flow.

Question 12

arterioles function

Answer 12

Link the arteries and capillaries

Vasoconstriction – smooth muscle in the arteriole contracts and constricts the vessel preventing blood flowing into a capillary bed

Vasodilation – smooth muscle in wall of arteriole relaxes and blood flows through into the capillary bed

Question 13

capillaries structure and adaptations

Answer 13

Very small lumen – forces blood to travel slowly which provides more opportunity for diffusion to occur

A large number of capillaries branch between cells – substances can diffuse between the blood and cells quickly as there is a short diffusion distance

Wall of capillary made solely from a single layer of endothelial cells – wall is only one cell thick so reduces diffusion distance for oxygen and carbon dioxide between the blood and the tissues of the body. White blood cells can combat infection in affected tissues by squeezing through the intercellular junctions in the capillary walls.

Provide a very large surface area for the diffusion of substances into and out of the blood

Question 14

capillaries function

Answer 14

Microscopic blood vessels that link the arterioles and venules

Form an extensive network through all the tissues of the body

Substances are exchanged through the capillary walls between the tissue cells and the blood

Question 15

veins structure

Answer 15

Tunica media is much thinner in veins, and there is no need for thick muscular layer as veins don’t have to withstand high pressure

Lumen in vein is much larger than that of an artery

Veins contain valves

A pulse is absent in veins

The walls contain lots of collagen and relatively little elastic fibres

Question 16

veins function

Answer 16

Transport blood to the heart (usually at low pressure) away from the cells of the body

They carry deoxygenated blood except from pulmonary vein which carries oxygenated blood from the lungs to the heart

Question 17

veins adaptations

Answer 17

Veins contain valves to prevent the backflow of blood

Many of the bigger veins run between the big, active muscles in the body. When the muscles contract they squeeze the veins, forcing the blood towards the heart. The valves prevent backflow when the muscles relax

The breathing movements of the chest act as a pump. The pressure changes and the squeezing actions move blood in the veins of the chest and abdomen towards the heart

Question 18

venules structure

Answer 18

Have few or no elastic fibres and a large lumen

As the blood is at a low pressure after passing through the capillaries there is no need for a muscular layer

Have very thin walls with just a little smooth muscle

Question 19

venules function

Answer 19

Link the capillaries with the veins