6.8 Exchange of gases in lungs

Question 1

What is the site of gas exchange in mammals

Answer 1

The epithelium of the alveoli
Situated in the lungs

Question 2

How are the alveoli adapted for gas exchange

Answer 2

. Tiny air sacs to give large surface area to volume ratio

. Moist lining to dissolve the gases so they can diffuse quickly

. Next to capillaries for a good blood supply to maintain diffusion gradient between the alveolar surface and the blood capillary which carries the oxygen away to the body

. Short diffusion gradient as the alveolar wall and the capillary are both one cell thick so there is quick and efficient transport

Question 3

Why are the alveoli in the lungs, and the lungs in the body

Answer 3

As they are very thin, they are delicate so can be easily damaged , so are located there for protection

Question 4

How are the capillaries adapted for gas exchange in lungs

Answer 4

. They are so narrow that the red blood cells are flattened against capillary walls in order to squeeze through

This slows down the red blood cells as they pass so there is more time for diffusion
This reduces the distance between alveoli and red blood cells as they are flattened against capillary walls

. The walls are only one cell thick of both capillaries and alveoli so short diffusion pathway

. Alveoli and pulmonary capillaries have a large surface area

Question 5

How is a steep concentration gradient maintained in the lungs

Answer 5

Breathing movements ventilate the lungs

The heart constantly circulates blood around the alveoli

So this ensures there is a steep concentration gradient of oxygen and CO2

Question 6

What are 5 risk factors for lung disease

Answer 6

. Smoking (90% of cases have been heavy smokers)

. Air pollution

. Genetic make up

. Infections

. Occupation eg working with harmful chemicals that are inhaled