6.6 Structure of the human gas-exchange system

Question 1

Why do aerobic organisms require a constant supply of oxygen ?

Answer 1

All aerobic organisms require a constant supply of oxygen to release energy in the form of ATP during respiration.

Question 2

Why is the volume of oxygen absorbed and volume of co2 to be removed large in mammals?

Answer 2

1. they are relatively large organisms with a large volume of living cells
2. they maintain a high body temperature which is related to them having high metabolic and respiratory rates

Question 3

Where is the site of gas exchange in mammals and why is it located inside the body?

Answer 3

Lungs.
They are located inside the body because air is not dense enough to support and protect these delicate structures + the body as a whole would otherwise lose a great deal of water and dry out.

Question 4

What supports and protects the lungs?

Answer 4

Ribcage

Question 5

What are the 5 main parts of the human gas-exchange system and their structure and function?

Answer 5

1. Lungs
   - lobed structures made up of a series of highly branched tubules called bronchioles which end in tiny air sacs called alveoli
2. Trachea
   - flexible airway supported by rings of cartilage. The cartilage prevents the trachea collapsing as the air pressure inside falls when breathing in. Tracheal walls are made up of muscle lined with ciliated epithelium and goblet cells.
3. Bronchi
   - 2 divisions of the trachea leading to a lung. Produce mucus to trap dirt particles and have cilia that move the dirt-laden mucus towards the throat. The larger bronchi are supported by cartilage, although the amount of cartilage is reduced as the bronchi get smaller
4. Bronchioles
   - series of branching subdivisions of the bronchi. Their walls are made of muscle lined with epithelial cells. This muscle allows them to constrict so that they can control the flow of air in and out of the alveoli.
5. Alveoli
   - minute air-sacs with a diameter of 100 and 300 micrometers at the end of the bronchioles. Between the alveoli there are some collagen and elastic fibres. The alveoli are lined with epithelium,. The elastic fibres allow the alveoli to stretch as they fill with air when breathing in. They can spring back during breathing out in order to expel the co2 rich air. The alveolar membrane is the gas-exchange surface.