Topic 2 - Gaseous Exchange

Question 1

What is the structure of a mammalian lung

Answer 1

Air leaves lungs from trachea, which leads into the thoracic cavity. This splits into two bronchi which branch into bronchioles. In these bronchioles is a cluster of alveoli

Question 2

How does gas exchange in a mammal occur

Answer 2

By diffusion

Question 3

What is the stages of inhalation

Answer 3

Muscular region of diaphragm contracts / external intercostal muscles contract
Diaphragm flattens / ribs move up and out
Volume of thorax increases
Pressure around lungs decrease
Pressure in alveoli decrease
Air enters lungs

Question 4

What is the stages of exhalation

Answer 4

Muscular region of diaphragm and external intercostal muscles relax
Diaphragm returns to some / ribs move down and in
Volume of thorax decreases
Pressure around lungs increases
Pressure in alveoli increase
Air leaves lungs

Question 5

How is gas diffuse rapid in mammalian lungs

Answer 5

Concentration gradient is maintained by ventilation of the lungs and blood flow through capillaries
Alveoli and capillaries have large surface area
Walls of alveoli are thin

Question 6

What enters and leaves in mammalian gas exchange

Answer 6

Oxygen enters
CO2 leaves

Question 7

What occurs during forced exhalation

Answer 7

Thoracic cavity reduces even further