3.2.4 Gas Exchange In Mammals (humans)

Question 1

What are the structures involved in the gas exchange system in humans

Answer 1

Lungs -> Trachea -> bronchi -> bronchioles -> alveoli -> alveolus

Question 2

How does the gas exchange surface maintain a large surface area in humans

Answer 2

Many alveoli, dense network of capillaries over each alveolus

Question 3

How does the gas exchange surface maintain a short diffusion pathway in humans

Answer 3

Capillary wall is one flattened endothelial cell thick, capillaries are really close to alveolus, alveolus wall is 1 squamous epithelial cell thick

Question 4

How does the gas exchange surface maintain a steep concentration gradient in humans

Answer 4

Blood flows away from alveolus taking oxygen with it, deoxygenated blood flows towards alveoli, diffusing carbon dioxide into alveolus, oxygen levels in alveoli kept higher than blood due to inhalation

Question 5

What is the function of the surfactant found in the alveolus, and how might similar artificial surfactant have a medical use

Answer 5

Keeps alveoli open, to assist breathing in premature babies

Question 6

How does Ventilation affect gas exchange

Answer 6

Maintains the concentration gradient, respiratory medium always flows down a pressure gradient, so we have to make the pressure in our body lower than the pressure outside (by increasing volume) for air to move in - inhalation, and vice versa for exhalation

Question 7

Describe how ventilation works in humans

Answer 7

Antagonistic intercostal muscles - internal and external, movement of ribs, contraction or relaxation of diaphragm, changes in thoracic volume and pressure, movement of air out or in