Blood Vessels 8.2

Question 1

Structural components of blood vessels

Answer 1

Elastic fibres so that the blood vessels can stretch and return back to their normal size, making them flexible
Smooth muscle so the blood vessels can contract and relax, adjusting its size.
Collagen can provide structural support to maintain the shape of the vessel

Question 2

Arteries

Answer 2

This carries blood away from the heart to the rest of the body and carries oxygenated blood unless it’s the pulmonary artery. They are usually under high pressure
The layers of the artery are the collagen layer on the outside, smooth muscle, an elastic layer, endothelium.
The elastic layer is the most important as it allows the artery to stretch and it’s lumen to get bigger to increase blood flow, but also recoil and return to its normal size to keep the blood flow constant in between heart contractions.

Question 3

Arterioles

Answer 3

They link arteries and capillaries together. Arterioles have more smooth muscle than in arteries which can control the flow of blood to certain organs.

Question 4

Vasoconstriction

Answer 4

When the blood vessels smooth muscle contracts and reduces the size of the lumen which constricts blood to a certain place

Question 5

Vasodilation

Answer 5

When the blood vessels smooth muscle relaxes and increases the size of the lumen, so more blood can flow through.

Question 6

Capillaries

Answer 6

They are a microscopic network of tubules that connect the arterioles to the venules. Oxygenated blood will enter and when it leaves it will be deoxygenated. The lumen is so small that only one blood cell will take up the whole diameter. It has really cell walls that are one cell thick so that the diffusion rate is big. They have a large surface area and are quite long compared to the arterioles which slow down the flow of blood so that more gas exchange can occur

Question 7

Veins

Answer 7

These carry blood away from the cells and back to the heart under slightly lower pressure. It receives deoxygenated blood from the venules and contains a large amount of your blood at one time. Veins have valves to protect against the backflow of blood. Their walls contain a lot of collagen and not as much smooth muscle or elastin and they also have a large lumen.

Question 8

Venules

Answer 8

These take deoxygenated blood from the capillaries and move it to the veins. They have very thin walls and not a lot of smooth muscle because it is not under a lot of pressure.

Question 9

How are veins adapted to move blood?

Answer 9

Because blood is under low pressure in the veins and has to move against gravity, the veins have to be adapted to prevent backflow of blood etc.
The majority of veins have inner flaps that are extensions of the inner lining. They keep the blood flowing in the direction towards the heart, and if blood starts flowing the other way, the valve will close to prevent backflow. Veins also run between your arms and legs so when your muscles contract, they will squeeze the veins and the blood will be moved towards the heart. The moving of your chest cavity also moves blood up to your chest.