2.5 The structure and function of veins, capillaries and arteries

Question 1

Identify the three different types of blood vessels that make up the circulatory system.

Answer 1

The circulatory system is made up of three types of blood vessels; arteries, capillaries and veins and the movement of blood through these vessels is powered by a pump called the heart.

Question 2

Where does the pulmonary vein take blood.
(Circuit of the circulatory system) 1

Answer 2

Blood is oxygenated as it travels through the lungs. When oxygenated blood leaves the lungs, it travels in the pulmonary vein and is carried into the left atrium of the heart.

Question 3

How is the oxygenated blood supplied to the body tissues
(Circuit of the circulatory system) 2

Answer 3

Blood then flows from the left atrium into the left ventricle and is pumped out of the left ventricle into the aorta which supplies the oxygenated blood to the body tissues.

Question 4

Where does the vena cava deliver blood
(Circuit of the circulatory system) 3

Answer 4

The body tissues carry out respiration, using up the oxygen and producing carbon dioxide. The blood is now deoxygenated, and it is returned from the body tissues to the heart in the vena cava. The vena cava delivers blood into the right atrium.

Question 5

Where does the pulmonary artery carry blood
(Circuit of the circulatory system) 4

Answer 5

Blood then flows from the right atrium into the right ventricle before being pumped out of the heart into the pulmonary artery. The pulmonary artery carries the deoxygenated blood up to the lungs where the blood will become oxygenated again.

Question 6

where does blood circulate

Answer 6

Blood circulates from the heart through the arteries into the capillaries and then through the veins and back to the heart

Question 7

State the function of arteries and describe the changes in pressure that occur as blood travels around the circulation system.

Answer 7

Arteries carry blood away from the heart under high pressure. Arteries divide into smaller and smaller blood vessels called arterioles and then capillaries.

Question 8

State the function of capillaries and describe the changes in pressure that occur as blood travels around the circulation system.

Answer 8

The capillaries form a network that allows exchange of materials with body cells. Blood enters the capillary network under high pressure but then loses pressure so that by the time that the blood exits the capillary bed it is under low pressure.

Question 9

State the function of capillaries and describe the changes in pressure that occur as blood travels around the circulation system.

Answer 9

Blood leaves the capillary network in small veins called venules and these join up to form bigger veins. Veins carry blood back to the heart under low press

Question 10

Explain why a pulse can be felt in an artery

Answer 10

The elastic walls of the arteries stretch and recoil to accommodate the surge of blood that passes through the artery after each contraction of the heart. This stretch and recoil of the elastic fibres within the thick muscular walls of the artery is what is felt as a pulse.

Question 11

What is the central lumen

Answer 11

All blood vessels have a central lumen – the area where the blood flows
The central lumen is lined by a layer of cells called the endothelium.

Question 12

What is the endothelium surrounded by

Answer 12

In arteries and veins the endothelium is then surrounded by further layers of tissue. The outermost layer is composed of connective tissue containing elastic fibres. The middle layer contains smooth muscle with more elastic fibres.

Question 13

Arteries walls are….

Answer 13

When compared, the arteries have much thicker muscular walls and a smaller central lumen than veins. The other major structural difference between arteries and veins is that only veins contain valves.

Question 14

Capillarie structure

Answer 14

Capillaries allow exchange of substances with tissues.

Capillary walls are only one endothelial cell thick.

Question 15

What are clefts?

Answer 15

Clefts / slits between the endothelial cells allow materials to pass in and out of the capillary.

Only one red blood cell at a time can fit through the central lumen of a capillary.

Question 16

What is exchanged between the lumen of the capillary

Answer 16

Materials are exchanged between the lumen of the capillary and the tissue fluid surrounding the body cells.

Question 17

Where are the valves located

Answer 17

Valves are found between the atria and ventricles, between the ventricles and the arteries leaving the heart and within veins

Question 18

What are the function of valves

Answer 18

The function of valves is to prevent the backflow of blood between heartbeats.

Question 19

How do valves operate

Answer 19

The valves are forced open when the heart beats to let the blood move forward. The valves then close when the heart relaxes to prevent the blood flowing back down the vein / into the previous chamber under the force of gravity.

Question 20

How is blood flow regulates

Answer 20

Blood flow can be regulated using the nervous system to send nerve impulses to the smooth muscle tissue of the arteries

Question 21

What is it called when the smooth muscles contact

Answer 21

The signals can cause the smooth muscle to contract, this is called vasocontraction and will decrease the blood flow through the artery by reducing the diameter of the lumen

Question 22

What happens when the smooth muscles relax

Answer 22

Alternatively, the signals can cause the smooth muscle to relax, this is called vasodilation and will increase the blood flow through the artery by increasing the diameter of the lumen

Question 23

What are vasoconstriction and vasodilation used for

Answer 23

Vasoconstriction and vasodilation are mechanisms used to redistribute blood flow to body organs during different activities and they are also used during thermoregulation.

Question 24

Describe the exchange of materials between blood vessels and body cells.

Answer 24

Materials are exchanged between the blood capillaries and tissue fluid surrounding the body cells.

Question 25

What direction does the exchange between blood vessels and body cells happen

Answer 25

This happens in both directions. The initial exchange of materials from the capillaries happens due to pressure filtration of the blood plasma through the capillary walls into the tissue fluid

Question 26

What does the tissue fluid supply the body with?

Answer 26

The tissue fluid then supplies body cells with glucose, oxygen and other substances needed for cell metabolism. Carbon dioxide and other metabolic wastes diffuse out of the body cells and into the tissue fluid.

Question 27

What is glucose, oxygen and other substances exchanged back into

Answer 27

These materials are then exchanged back into the blood plasma when tissue fluid is reabsorbed back into the blood capillaries.

Question 28

State the role of lymph vessels in the circulation system

Answer 28

Lymphatic vessels absorb excess tissue fluid that is not reabsorbed into the capillary network. They transport their lymph fluid for eventual return to the circulatory system.

Question 29

Compare the composition of blood plasma and tissue fluid.

Answer 29

Blood plasma and tissue fluid both carry almost the same materials e.g. glucose, O2, CO2 and amino acids. However, the main difference is that tissue fluid does not contain the plasma proteins that would be found in blood plasma. Plasma proteins are too large to move through the blood capillary walls during pressure filtration.