This definitions covers Key Definitions within Gas Exchange in Humans for GCSE Biology. Lung structure, alveoli adaptations, breathing mechanism, gas transport in blood, and effects of smoking It is section 12 of 19 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 12 of 19
Practice
19 questions
Recall
23 flashcards
Key Definitions
Gas exchange: The process by which oxygen moves from the alveoli into the blood and carbon dioxide moves from the blood into the alveoli, both by diffusion down concentration gradients.
Alveolus (plural: alveoli): Tiny, thin-walled, moist air sacs at the ends of bronchioles in the lungs, adapted to maximise the rate of gas exchange between air and blood.
Trachea: The main airway that carries air from the throat to the bronchi; supported by C-shaped rings of cartilage that prevent it collapsing when you breathe in.
Bronchi (singular: bronchus): The two airways that branch from the trachea, carrying air into the left and right lungs.
Bronchioles: Smaller airways that branch repeatedly from the bronchi and carry air to clusters of alveoli.
Diaphragm: A dome-shaped sheet of muscle below the lungs that contracts and flattens during inhalation to increase thoracic volume and draw air into the lungs.
Intercostal muscles: Muscles between the ribs that contract (external intercostals) during inhalation to raise the rib cage and increase lung volume.
Concentration gradient: The difference in concentration of a substance between two regions; diffusion always occurs from an area of higher concentration to an area of lower concentration, down the gradient.