Blood Vessels

Question 1

What do arteries do

Answer 1

They carry blood away from the heart to the organs

Question 2

What is blood in the arteries under

Answer 2

High pressure

Question 3

What happens when the heart beats and what is it called

Answer 3

A surge of even higher pressure blood is pushed down the arteries and this is called the pulse

Question 4

What is a feature of the blood in arteries

Answer 4

It is always moving forward even between heart beats.

Question 5

What is the average diameter of an artery

Answer 5

4-10mm

Question 6

What is a feature of the artery wall and why

Answer 6

The artery wall is very thick allowing the artery to withstand the high pressure of the blood.

Question 7

What does the artery wall consist of

Answer 7

several layers

Question 8

What is the outer layer made up of and why

Answer 8

It has a collagen rich outer layer. And the collagen plays a structural role, strengthening the artery wall against the pressure of the blood.

Question 9

What is the 2nd layer of the artery made out of and what does it do

Answer 9

Smooth muscle , and when the smooth muscle contracts the diameter of the artery narrows allowing the body to control how much blood flows through different organs.

Question 10

What do smaller arteries have compared to larger arteries and why

Answer 10

They tend t have a greater proportion of smooth muscle compared to larger arteries because they have a greater role in controlling blood flow.

Question 11

What is the 3rd layer of arteries made out of

Answer 11

It is a layer rich in elastic fibres and the elastic fibres. Contain the protein called elastin which can stretch.

Question 12

What occurs to the elastic fibres when the heart beats.

Answer 12

When the heart contracts a surge of high pressure blood passes through the artery as the surge moves through the elastic fibres stretch. They then recoil once the surge has passed. The elastic recoil helps to keep the blood moving smoothly forward in between contractions of the heart.

Question 13

What is the central cavity of the artery called and what does it do

Answer 13

It is called the lumen and it is where the blood flows through

Question 14

What is the lumen lined with

Answer 14

A thin layer of endothelial cells, presenting a very smooth surface to reduce friction as the blood flows through.

Question 15

What do arteries branch into

Answer 15

Smaller blood vessels called arterioles.

Question 16

What is the job of the arterioles

Answer 16

Is to deliver blood to capillaries.

Question 17

What is similar about the walls of arterioles and arteries and what is different

Answer 17

The walls of the arterioles contain the same layers as arteries. However, they differ in their relative thickness, having a diameter of around 50uM.

Question 18

What is the difference in pressure in arteries and arterioles and the thickness of the elastic layer

Answer 18

In arterioles the blood pressure is lower than in arteries and the elastic layer is relatively thin compared to arteries.

Question 19

What is the smooth muscle layer in arteries compared to arterioles

Answer 19

It is relatively thicker in arterioles compared to arteries
As they are involved in controlling the amount of blood that passes through capillaries.

Question 20

What happens when the smooth muscle in arterioles contracts and relaxes

Answer 20

When the smooth muscle in the arterioles contracts, blood flow through capillaries is reduced, called vasoconstriction.

When the smooth muscle is arterioles relaxes, blood flow through capillaries increases, called vasodilation.

Question 21

When does vasodilation occur

Answer 21

Takes place when an organ requires an increased amount of oxygen.

Question 22

What is present in every organ and tissue

Answer 22

Extensive networks of capillaries

Question 23

What is a feature of capillaries and what is a network of them called

Answer 23

The capillaries are extensively branched
A network of capillaries is called a capillary bed

Question 24

What occurs in the capillary bed

Answer 24

It is where substances are exchanged between the blood and the body cells

Question 25

What substances move where in the capillary bed

Answer 25

Oxygen and glucose move from the blood to the body cells while waste products like urea and CO2 diffuse from cells back to the blood.

Question 26

What does the branching of capillaries do and what have capillaries evolved to do

Answer 26

The extensive branching of capillaries provides a massive surface for the exchange of materials And capillaries have evolved to maximise the rate of diffusion.

Question 27

What is the structure of capillaries

Answer 27

Capillary walls are very thin and only consist of a single layer of endothelial cells. On the outside of the capillary there is a very thin membrane called the basement membrane.

Question 28

What are adaptations of capillaries (1)

Answer 28

As capillary walls only consist of a single layer of cells there is a very short diffusion distance between the blood and the cells near the capillary. Increasing the rate of diffusion.

Question 29

What are adaptations of the capillary (2)

Answer 29

The diameter of a capillary lumen is only slightly greater than that of a red blood cell, so when red blood cells pass through capillaries they are pressed against the capillary walls reducing the distance for diffusion of O2. It also means that red blood cells travel through capillaries one at a time.

Question 30

What are present in the capillary walls

Answer 30

There are small gaps between endothelial cells, allowing the fluid to pass out of the blood. This is called tissue fluid and it bathes the cells providing essential molecules like glucose and amino acids.

Question 31

What is the 2nd function of the gaps in the capillary walls

Answer 31

They also allow white blood cells to leave the bloodstream

Question 32

What occurs once the blood has passed through the capillary bed

Answer 32

It then makes its way into very small veins called venules. These connect to larger veins, which carry deoxygenated blood to the vena cava where it passes into the heart.

Question 33

What is a feature of the blood travelling in veins and venules

Answer 33

They are under low pressure and is not travelling in pulses

Question 34

What are some differences between veins and arteries (1)

Answer 34

They have a thinner wall than arteries as they don’t have to withstand high pressures Veins have a larger lumen - so carry a greater volume of blood compared to arteries The smooth muscle layer and elastic layer are thinner in veins compared to arteries too

Question 35

What are some comparisons between veins and arteries (2)

Answer 35

There is no elastic recoil in veins The lumen of veins has a thin lining of endothelium cells, and this surface reduces friction between the blood and the wall of the vein like in arteries.

Question 36

What is an adaptation of veins

Answer 36

They contain valves which keep blood moving in the forward direction.

Question 37

What is a feature of the direction that blood may travel in veins

Answer 37

because the blood in the veins is travelling back to the heart it may be moving against gravity. And because the blood in the veins is travelling slowly and is under low pressure this makes movement very slow.

Question 38

How do veins solve the problem of slow transport against gravity

Answer 38

Many veins are found between skeletal muscles and when they contract they squeeze the veins between them, and because veins have a thin wall they change shape and the squeezing forces the blood along.

Question 39

What do the valves do when blood travels in different directions

Answer 39

If the blood moves forward they remain open. If the blood moves backwards then they shut.

Question 40

What does the combined effect of valance and muscle squeezing do

Answer 40

Moves blood towards the heart

Question 41

What is another way that helps blood to move towards the heart (inhalation)

Answer 41

When we inhale the pressure in the cavity decreases. This decrease in pressure helps to move blood in the chest veins towards the heart.