The Lungs (AQA GCSE Combined Science: Trilogy: Biology): Revision Note
Exam code: 8464
The lungs
The lungs are organs that carry out gas exchange
Ribs:
Bones that surround and protect the lungs
Intercostal muscles:
Muscles between the ribs which contract and relax to enable breathing in and out
Diaphragm:
Sheet of connective tissue and muscle that contracts and relaxes to change the volume of the thorax; this aids inhalation and exhalation
Trachea:
Windpipe that connects the mouth and nose to the lungs
Lining produces mucus and is lined with ciliated cells to protect against pathogens
Bronchus (plural bronchi):
Tubes branching off the trachea; one bronchus leads to each lung
Also produce mucus and lined with ciliated cells
Bronchioles:
The bronchi split to form smaller tubes that connect to each alveolus
Alveoli (singular alveolus):
Tiny air sacs where gas exchange takes place
Adaptations for gas exchange
Gas exchange occurs via diffusion, so the adaptations that aid gas exchange maximise the rate of diffusion
The lungs are adapted for gas exchange as follows:
Feature | Explanation |
|---|---|
Many alveoli | A large surface area is available for diffusion |
Alveolar walls are one cell thick | A short diffusion distance maximises the rate of diffusion |
Alveoli are surrounded by capillaries | A good blood supply ensures that a concentration gradient is maintained |
Continuous ventilation | Ensures constant supply of oxygen and removal of carbon dioxide in order to maintain a concentration gradient |
Examiner Tips and Tricks
Make sure that you can clearly link the features of the lungs to their function.
Never say that the alveoli have 'thin cell walls', as this is incorrect. Instead you should say that the walls of the alveoli are one cell thick.
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