The Alveolus
- The lungs are the gas exchange surface in humans
- They are adapted to maximise the exchange of gas by diffusion
- Inside the lungs there are many air-filled structures called alveoli
- Alveoli are found at the end of the bronchioles
- They consist of many individual sacs, each of which is called an alveolus
- Each alveolus has a single-celled wall with a moist lining
- The alveoli are surrounded by a network of capillaries containing red blood cells and plasma
- Oxygen diffuses into the blood from the alveoli
- Carbon dioxide diffuses out of the blood into the alveoli
- Alveoli are found at the end of the bronchioles
Alveoli structure diagram
Alveoli contain many sac-like structures each of which is a single alveolus
Examiner Tip
You need to be able to label the following structures on a diagram of the alveoli:
- End of bronchiole
- Wall of alveolus
- Moist lining of alveolus
- Wall of capillary
- Red blood cells and plasma
