OrganisationKey Facts

The Breathing Mechanism

Part of Gas Exchange in Humans · GCSE GCSE Biology revision

This key facts covers The Breathing Mechanism 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 5 of 19 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 5 of 19

Practice

21 questions

Recall

23 flashcards

The Breathing Mechanism

Inspiration (Breathing In)

Step 1: Diaphragm contracts and flattens (moves down)

Step 2: External intercostal muscles contract, lifting ribs up and out

Step 3: Chest cavity volume increases

Step 4: Pressure inside lungs decreases (below atmospheric pressure)

Step 5: Air rushes in through airways to equalize pressure

Expiration (Breathing Out)

Step 1: Diaphragm relaxes and returns to dome shape (moves up)

Step 2: External intercostal muscles relax, ribs move down and in

Step 3: Chest cavity volume decreases

Step 4: Pressure inside lungs increases (above atmospheric pressure)

Step 5: Air is pushed out through airways

Note: Normal expiration is passive (requires no energy), but forced expiration involves contraction of internal intercostal muscles and abdominal muscles.

Keep building this topic

Read this section alongside the surrounding pages in Gas Exchange in Humans. That gives you the full topic sequence instead of a single isolated revision point.

Alveolus Structure (Microscopic View)Gas Transport in Blood The Breath of Life: Gas Exchange Respiratory System Structure

Practice Questions for Gas Exchange in Humans

Which is the correct order of structures air passes through to reach the lungs?

A. Trachea → bronchi → bronchioles → alveoli
B. Bronchi → trachea → bronchioles → alveoli
C. Trachea → bronchioles → bronchi → alveoli
D. Bronchioles → bronchi → trachea → alveoli

1 markfoundation

Explain how the structure of alveoli is adapted for efficient gas exchange.

4 marksstandard

Quick Recall Flashcards

What are alveoli?

Tiny air sacs in the lungs where gas exchange takes place - oxygen enters the blood and carbon dioxide leaves

What is the trachea?

The main airway (windpipe) that carries air from the throat to the lungs, reinforced with cartilage rings

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Alveolus Structure (Microscopic View)

Gas Transport in Blood