Gas exchange

Question 1

Features of Gas Exchange Surfaces

Answer 1

Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster

Question 2

Function of Cartilage in the Trachea

Answer 2

Rings of cartilage surround the trachea (and bronchi)
The function of the cartilage is to support the airways and keep them open during breathing
If they were not present then the sides could collapse inwards when the air pressure inside the tubes drops

Question 3

Explain the function of diaphragm

Answer 3

The diaphragm is a thin sheet of muscle that separates the chest cavity from the abdomen; it is ultimately responsible for controlling ventilation in the lungs
When the diaphragm contracts it flattens and this increases the volume of the chest cavity (thorax), which consequently leads to a decrease in air pressure inside the lungs relative to outside the body, drawing air in.
When the diaphragm relaxes it moves upwards back into its domed shape and this decreases the volume of the chest cavity (thorax), which consequently leads to an increase in air pressure inside the lungs relative to outside the body, forcing air out

Question 4

Explain what happens during inhalation and exhalation

Answer 4

During inhalation the external set of intercostal muscles contract to pull the ribs up and out:
This also increases the volume of the chest cavity (thorax), decreasing air pressure, drawing air in
During exhalation, the external set of intercostal muscles relax so the ribs drop down and in:
This decreases the volume of the chest cavity (thorax) increasing air pressure, forcing air out