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Auralith Learning

Year 8 · Science · Breathing and respiration · Lesson 1

Breathing and gas exchange

The parts of the gas exchange system, how we breathe in and out, gas exchange in the alveoli, and the differences between inhaled and exhaled air.

Whiteboard video lesson: Breathing and gas exchange

25-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

  • Label the gas exchange system
  • Describe breathing in and out
  • Explain gas exchange in the alveoli
  • Explain how alveoli are adapted
  • Compare inhaled and exhaled air

The method

  1. Air passes through the trachea, bronchi and bronchioles to the alveoli.
  2. Breathing in: rib muscles contract, ribs move up and out, diaphragm flattens; pressure falls and air rushes in.
  3. In the alveoli, oxygen diffuses into the blood and carbon dioxide diffuses out.
  4. Alveoli have a large surface area, thin walls, are moist and have a good blood supply.

Key words: trachea, bronchi, bronchioles, alveoli, diaphragm, ribs, diffusion, gas exchange, inhale, exhale.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

Look at the diagram. Name the part labelled A, and give its job.

  1. Step 1: Find the label
  2. Step 2: A = bronchi
  3. Step 3: Job: carry air into each lung

Answer: Bronchi: carry air into each lung

Question 2

Look at the diagram. Name the part labelled B, and give its job.

  1. Step 1: Find the label
  2. Step 2: B = diaphragm
  3. Step 3: Job: muscle that helps us breathe

Answer: Diaphragm: muscle that helps us breathe

Question 3

Look at the diagram. Name the part labelled C, and give its job.

  1. Step 1: Find the label
  2. Step 2: C = ribs
  3. Step 3: Job: protect the lungs; help breathing

Answer: Ribs: protect the lungs; help breathing