6.6 Structure of the human gas exchange system

Question 1

Why do mammals require such a large volume of oxygen in/CO2 out?

Answer 1

• they are large with lots of living cells

- they maintain high body temperature so have high metabolic and respiratory rates.

Question 2

Why are the lungs located inside the body?

Answer 2

• They are delicate and air isn’t dense enough to support them
• It stops the body losing too much water

Question 3

Describe the lungs.

Answer 3

Lobed structures made up of bronchioles which branch into alveoli.

• supported by the rib cage
• ventilated by a constant stream of air.

Question 4

Describe the trachea.

Answer 4

A flexible airway supported by rings of cartilage which stop it collapsing when pressure falls.
- tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells.

Question 5

Describe the bronchi.

Answer 5

2 divisions of the trachea, similar to it in structure,

• produce mucus to trap dirt, and cilia to move it towards the throat.
• cartilage is reduced as bronchi get smaller.

Question 6

describe the bronchioles.

Answer 6

Branching subdivisions of the bronchi.

• walls are made of muscle lined with epithelial cells.
• the muscle allows them to constrict and move air in and out of the alveoli.

Question 7

describe the alveoli.

Answer 7

Tiny air sacks at the end of the bronchioles.

• Between alveoli are collagen and elastic fibers, allowing them to stretch when filling with air, and hold more.
• the alveolar membrane is the gas exchange surface.