6.4 - Gas Exchange

Question 1

What are the 3 key processes in physiological respiration?

Answer 1

• Ventilation
• Gas exchange
• Cell respiration

Question 2

Define ventilation.

Answer 2

The physical exchange of air between the atmosphere and the lungs, achieved by breathing.

Question 3

Define gas

Answer 3

The exchange of gas (carbon dioxide and oxygen) between the alveoli and the bloodstream.

Question 4

Define cell respiration.

Answer 4

The release of energy in the form of ATP from organic molecules (glucose).

Question 5

What is the purpose of ventilation?

Answer 5

Oxygen is consumed by cells during respiration and carbon dioxide is produced as a waste product.

This means O2 is constantly being removed from the alveoli into the bloodstream.

The lungs function as a ventilation system by continually cycling fresh air into the alveoli from the atmosphere.

This means O2 levels stay high in alveoli (and diffuse from the air into the blood) and CO2 levels stay low (and diffuse from the blood into the air)

Therefore, ventilation is needed to maintain a CONCENTRATION GRADIENT in the alveoli.

Question 6

Draw the lungs.

Answer 6

Great :D

Question 7

Draw an a alveolar and associated capillary.

Answer 7

Perfect!

Question 8

Explain the structure of an alveoli, relating it to its function.

Answer 8

• very thin epithelial layer (one cell thick) to minimise diffusion distances for gases
• surrounded by a rich capillary network to increase gas exchange with the blood
• spherical in shape to maximise surface area for gas exchange
• internal surface is covered with a layer of fluid, as dissolved gases are better able to diffuse into the bloodstream

Question 9

Define alveoli.

Answer 9

A cluster of air sacs at the end of bronchioles where gas exchange with the bloodstream occurs.

Question 10

Compare and contrast type I and type II pneumocytes.

Answer 10

Type I

• involved in the process of gas exchange between the alveoli and the capillaries
• flattened in shape and extremely thin to minimise diffusion distance for gases
• connected by junctions, which prevents the leakage of fluid into th air space

Type II

• secrete pulmonary surfactant, which reduces surface tension in the alveoli
• cube in shape and possess many granules (for storing surfactant components)
• make up 60% of total cells

Question 11

What is the purpose of a pulmonary surfactant?

Answer 11

Reduces surface tension and ensures that all the alveoli inflate at roughly the same rate.

Question 12

Why are alveoli moist, and what issue can arise with this..

Answer 12

The alveoli are moist so that gases can dissolve across the liquid - however this fluid surface reduces the surface area… - therefore a pulmonary surfactant is necessary to reduce surface tension.

Question 13

Gases move from a region of _____ pressure to _____ pressure.

Answer 13

High to low pressure

Question 14

When the pressure in the chest is less than the atmospheric pressure (or pressure in the air), air will ….

Answer 14

… Move into the lungs/Inspiration

Question 15

When the pressure in the chest is higher than the atmospheric pressure, air will …

Answer 15

… Move out of the lungs/Expiration

Question 16

An increased volume of air inside the chest _______ the pressure inside the chest.

Answer 16

Lowers. Air moves into the lungs.

Question 17

Muscles can _______ or ______ the volume of air inside the chest.

Answer 17

Increase or decrease

Question 18

A decreased volume of air inside the chest ______ the pressure inside the chest.

Answer 18

Increases. AIr moves out of the lungs.

Question 19

As volume decreases, pressure _____.

Answer 19

Increases.

Question 20

During inspiration, which muscles are contracting?

Answer 20

DIaphragm muscles contract.

External intercostal muscles contract.

Question 21

What happens to the chest cavity and diaphragm during inspiration?

Answer 21

Diaphragm flattens and chest cavity increases which reduces pressure. Air will want to move in.

Question 22

During expiration, which muscles are contracting?

Answer 22

Internal intercostal muscles contract.

Abdominal muscles contract.

Question 23

During expiration, which muscles are relaxed?

Answer 23

Diaphragm muscles relax.

Question 24

What happens to the chest cavity and diaphragm during expiration?

Answer 24

DIaphragm curves upwards and chest cavity decreases which increases pressure. Air will move out.

Question 25

What are the causes of lung cancer?

Answer 25

• Radiation
• Smoking
• Age
• Pollution
• Genetics

Question 26

What are consequences of lung cancer?

Answer 26

Inability to breathe, death

Question 27

What are the causes of emphysema?

Answer 27

The loss of elasticity in the walls of alveoli.

Question 28

What are the consequences of emphysema?

Answer 28

The loss of elasticity results in the ENLARGEMENT of the alveoli, leading to a LOWER total SURFACE AREA for gas exchange. It can also cause HOLES to develop and alveoli to MERGE into huge air spaces.

Leads to damaged lung tissue.

Question 29

What happens to the ventilation rate during exercise?

Answer 29

• Increases ventilation rate (more breaths allows for a more continuous exchange of gases)
• Increases tidal volume (increasing the volume of air taken in and out per breath allows for more air in the lungs to be exchanged)

Question 30

How can ventilation rate be measured?

Answer 30

Using a spirometer OR a more simpler method - a balloon.

A person breathes into a balloon and the volume of air exhaled is measured.
The volume of air can be determined by submerging the balloon in water and measuring the volume displaced (1ml = 1cm3).