Gas exchange in humans

Question 1

What are the parts in the human gas exchange system?

Answer 1

Trachea
Ribcage
Intercostal muscles 
Bronchus 
Bronchiole
Diaphragm 
Alveoli

Question 2

Where does the air go to as it enters through breathing?

Answer 2

Trachea

Question 3

What does the trachea split into?

Answer 3

2 bronchi

Question 4

What does the bronchi branch off into?

Answer 4

Bronchioles

Question 5

What are the two types of intercostal muscles?

Answer 5

External

Internal

Question 6

What is ventilation?

Answer 6

Process of inspiration (breathing in) and expiration (breathing out)

Question 7

What happens during inspiration?

Answer 7

External intercostal muscles and diaphragm contract, it flattens

Question 8

How does the ribcage move during inspiration?

Answer 8

Upwards and outwards

Question 9

How do the movements of the diaphragm and intercostal muscles affect volume and pressure? How does this affect the movement of air?

Answer 9

Volume increases
Pressure decreases
The air flows down the trachea down a pressure and diffusion gradient to an area of low pressure

Question 10

Is inspiration an active or a passive process?

Answer 10

Active

Question 11

What happens during expiration?

Answer 11

External intercostal muscles and diaphragm relax, it domes

Question 12

How does the ribcage move during expiration?

Answer 12

Downwards and inwards

Question 13

What happens to the volume and the pressure during expiration?

Answer 13

Volume decreases

Pressure increases

Question 14

Is expiration passive or active?

Answer 14

Passive

Question 15

What happens during forced expiration?

Answer 15

The external intercostal muscles relax and the internal intercostal muscles contract which pulls the ribcage further down and in

Question 16

What are alveoli?

Answer 16

Microscopic air sacs

Question 17

What surrounds alveoli?

Answer 17

Capillaries

Question 18

What is the structure of the alveoli?

Answer 18

Single, thin layer of alveolar epithelium cells

Question 19

What are the walls of capillaries made from?

Answer 19

Capillary endothelium

Question 20

What protein is in the walls of the alveoli?

Answer 20

Elastin

Question 21

How does elastin benefit the alveoli?

Answer 21

Helps alveoli return to normal shape after exhaling and inhaling air

Question 22

What diffuses out of the alveoli?

Answer 22

Oxygen

Question 23

What are the factors which affect the rate of diffusion?

Answer 23

A thin exchange surface - short diffusion pathway
A large surface area - there’s lots of alveoli, large area for exchange to take place
Concentration gradient

Question 24

What is there between the alveoli and the capillaries?

Answer 24

A steep concentration gradient of oxygen and carbon dioxide

Question 25

What are the two layers that the air has to diffuse across in order to get to the capillaries?

Answer 25

Alveolar epithelium | Capillary endothelium

Question 26

Just before a person starts to exhale, the composition of the air in an alveolus differs the composition of the air in the trachea. Give two ways in which the composition would differ. (1 marks)

Answer 26

1) More CO2 | 2) More O2 in alveoli

Question 27

Suggest why blood returning to the heart from the lungs contains some carbon dioxide (2 marks)

Answer 27

- Not all CO2 will diffuse into the lungs | - The concentration gradient will become equal when there is an equal amount of CO2 into the blood and the lungs

Question 28

Describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood (5 marks)

Answer 28

- Alveoli have a large surface area - Thin alveolar walls - Cell membrane permeable to gases - Wide trachea with cartilage rings - Capillary walls are thin

Question 29

Describe and explain the mechanism that causes forced expiration. (4 marks)

Answer 29

- external intercostal muscles and diaphragm are relaxed - Internal intercostal muscles contract - decreases the volume and increases the pressure - air is forced out down a pressure gradient, out of the lungs

Question 30

People who have been fire-breathers for many years often find they cannot breathe out properly. Explain why. (2 marks)

Answer 30

- Thick layers of scar tissue - Lose elasticity - Less recoil

Question 31

Explain how downward movement of the diaphragm leads to air entering the lungs (2 marks)

Answer 31

- Increases the volume - Decreases the pressure - Air moves in down pressure gradient