2.46 – Describe the structure of the thorax: the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes.
🏆 By the end I will be able to…
All: name the parts of the thorax and put the airway in order.
Most: describe what each structure does.
Some: explain how each structure is adapted to its job.
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Teacher Tools – Lesson 6
This lesson runs active — evidence is the per-pupil Match Report (Independent + Exit slides). Worksheets below are an optional paper fallback only.
⏱️ Before We Start · 60 sec
Before We Start: Why We Even Have a Breathing System
Quick recall, not new content. Last lessons you learned respiration — your cells release energy from glucose. Aerobic respiration needs a constant supply of oxygen and makes waste carbon dioxide. (It's on Side A of your bridge sheet.)
The job the breathing system has to do
Respiration only keeps going if oxygen keeps arriving and carbon dioxide keeps leaving. That's the breathing system's job.
1. Respiration happens in cells and needs a steady supply of oxygen.
2. That oxygen comes from the air → into the lungs → into the blood.
England beat Mexico 3–2 — and hung on with 10 men through 11 minutes of added time. The catch? That stadium sits 2,000+ metres up, where the air has roughly a third less oxygen. Every player was gasping.
Thinner air = harder to get O₂ = the breathing system on overtime 🫁
Talk — 20 seconds: Remember oxygen debt from last lesson? After a sprint you pant to pay it back. Those players paid a huge debt in thin air. Today we open up the machine that delivers all that oxygen — your thorax. If you're tired this morning, that's your thorax too. 😴
Arrival Task
Arrival Task – Recall from Respiration
Instructions: Answer from memory. Q1–3 recall respiration. Q4 leads into today.
🔄 Retrieval Grid — Recall from "Respiration Equations"
Quick recall: try all 4 before the teacher reveals answers. Keeps knowledge "sticky"!
1. Word equation for aerobic respiration?
Glucose + O₂ → CO₂ + H₂O (+ ATP)
2. What gas do we need to breathe in?
Oxygen
3. What gas do we breathe out?
Carbon dioxide
4. Why do we need to breathe?
To get O₂ for respiration / remove CO₂ waste
1. Respiration (Recall)
Write the word equation for aerobic respiration.
Glucose + Oxygen → Carbon Dioxide + Water (+ ATP)
2. ATP (Recall)
Name two things ATP provides energy for in cells.
Any two: muscle contraction, active transport, cell division, protein synthesis, nerve impulses, body temperature.
3. Anaerobic (Recall)
What does anaerobic respiration produce in animals?
Lactic acid.
4. Lead-in: Breathing
Aerobic respiration needs oxygen. How does oxygen get from the air outside into your blood?
Through the lungs / breathing system (the thorax).
1. Respiration (Recall)
Write the balanced symbol equation for aerobic respiration.
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
2. Differences (Recall)
State two differences between aerobic and anaerobic respiration.
Aerobic needs oxygen/anaerobic doesn't. Aerobic in mitochondria/anaerobic in cytoplasm. Aerobic makes lots of ATP/anaerobic makes little.
3. Oxygen Debt (Recall)
Explain what the oxygen debt is.
Extra oxygen needed after exercise to break down the lactic acid that built up during anaerobic respiration.
4. Lead-in: Breathing
Respiration needs oxygen and produces carbon dioxide. Suggest what the breathing system must do to keep respiration going.
It must bring oxygen into the blood and remove carbon dioxide from the blood (gas exchange).
1. Equations (Recall)
Write the word equations for anaerobic respiration in animals and in yeast.
Explain why respiration is NOT the same as breathing.
Respiration is a chemical reaction inside cells that produces ATP. Breathing (ventilation) is the physical movement of air in and out of the lungs.
3. Application (Recall)
Explain why muscle cells have more mitochondria than skin cells.
Muscle cells need more ATP for contraction, so they need more mitochondria to carry out more aerobic respiration.
4. Lead-in: Breathing
Aerobic respiration needs a constant supply of oxygen and must remove CO₂. Suggest why the breathing system needs structures with a very large surface area.
A large surface area allows more oxygen and CO₂ to be exchanged at once, keeping up with the demand from respiration in all cells.
Starter
Starter: Wake Up Your Thorax 🫁
First — 60 seconds, everyone in. Hand on your ribs, hand on your belly. Follow the circle. This wakes you up and shows you today's lesson happening in your own chest.
Tap start when you're ready
Feel it: ribs lifting = your intercostal muscles · belly pushing out = your diaphragm pulling down. You just used two structures we name today. Calm and awake — now let's warm up your memory. ⬇️
Now — no pressure! Tap a word, then tap the numbered clue it belongs to. Stuck? Tap 💡 letter for a hint. Gaps get filled together during the lesson.
Matched: 0/5
Word bank — tap one, then tap its clue:
Trachea
Bronchi
Alveoli
Lungs
Diaphragm
1tap ▶The tube air goes down…
2tap ▶Two branches splitting off the main tube…
3tap ▶Tiny air sacs (think bubbles)…
4tap ▶The big pink organs…
5tap ▶The sheet of muscle underneath…
Prefer paper? You can still label the printed diagram in your book — this is just to warm up your memory.
I Do
I Do: The Airway (Spec 2.46)
Key Idea: Air travels through a series of tubes that get smaller and smaller until it reaches the tiny air sacs (alveoli) where gas exchange happens.
The Air Pathway (biggest → smallest)
🌬️
Trachea (Windpipe) – the main tube that draws air into the lungs. Held open by C-shaped rings of cartilage.
↓
🔀
Bronchi (singular: bronchus) – the trachea splits into two bronchi, one going to each lung.
↓
🌿
Bronchioles – the bronchi split into many smaller tubes called bronchioles.
↓
🫧
Alveoli – tiny air sacs at the ends of bronchioles. This is where gas exchange happens.
The Thorax
trachea → bronchi → bronchioles → alveoli
🧠 Everyone stand — do the actions. "Tiny Beings Breathe Air" with your body. Follow the highlight, then we do it twice with no words.
🫸🫷Trachea one straight tube
✌️Bronchi splits into two
👐Bronchioles wiggle all fingers
😗Alveoli puff your cheeks
Each one gets smaller — like a tree trunk → branches → twigs → leaves. 🌳
Aspire: Why does the trachea have C-shaped rings of cartilage but the bronchioles don't? The trachea needs to stay permanently open (it's wide and could collapse). Bronchioles are tiny and embedded in lung tissue, which keeps them open. The C-shape also allows the oesophagus behind to expand when swallowing food.
Don't write:"Air goes into the lungs through the bronchitis."
Write:"Air enters through the trachea, then bronchi, then bronchioles, then reaches the alveoli."
"Bronchitis" is a disease! The structures are: bronchus (singular) / bronchi (plural). Spelling matters.
We Do
We Do: Find It on Your Own Body 🫵
Before the screen — stand up. Teacher calls a structure, you point to where it is on you (trachea = throat, ribs = cage, diaphragm = under the ribs…). Then a volunteer places the matching label on the board to confirm. Body first, board second.
Labels placed: 0/7
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Label Bank – click one, then click the correct hotspot:
Key Idea: The thorax has structures that protect the lungs, move air in and out, and keep everything working smoothly.
💡 Spot check — which TWO are muscle? Tap them:
Ribs
Intercostals
Diaphragm
Pleura
🦴 Ribs & Ribcage BONE
The ribcage is bone that protects the lungs and heart. Think crash helmet for your chest.
💪 Intercostal Muscles MUSCLE
Two sets between the ribs: external (outside) and internal (inside). They move the ribs up/down.
🫁 Diaphragm MUSCLE
A sheet of muscle at the bottom. It changes the volume of the thorax when breathing.
🧴 Pleural Membranes
Surround the lungs and make pleural fluid that lubricates them — less friction when they move.
Aspire: Why two sets of intercostals? They work antagonistically — external pull ribs up/out (breathe in), internal pull ribs down/in (breathe out).
💡 Real-World Link: Your ribs protect your lungs like a crash helmet protects your brain. But unlike a helmet, your ribcage can also move – thanks to the intercostal muscles. Without them, you couldn't breathe!
When labelling diagrams: use the exact spec word. Not "muscle between ribs" — write "intercostal muscles". Not "wind pipe" — write "trachea".
Watch & check: You've met the airway and the protective parts — now see them together. Use the toggle to switch, watch it light up, then finish the sentences. This is exactly what the match task needs next.
🌬️💨
Trachea windpipe
→
Bronchi 2 tubes
→
Bronchioles smaller
→
Alveoli air sacs
Air travels through tubes that get smaller and smaller, ending at the tiny alveoli where gas exchange happens.
Ribs (bone) protect · intercostals + diaphragm (muscle) will move air · pleural membranes lubricate.
We'll see HOW these move air in the next lesson — Ventilation.
Switch demos with the toggle; replay with Run demo.
Listen for the exact words: trachea (not "windpipe"), bronchi/bronchus (not "bronchitis"), alveoli (not "air bags").
✍️ Now finish these — say it out loud first, then jot it down:
Air's path: trachea → ____________ → ____________ → ____________. Gas exchange happens in the ____________.
The ribs are made of ____________ and their job is to ____________. The diaphragm is made of ____________.
Air: trachea → bronchi → bronchioles → alveoli; gas exchange in the alveoli. Ribs = bone, they protect the lungs/heart. Diaphragm = muscle.
Ready check: Cover the screen — can you say the airway order AND name one part that protects and one that moves air? If yes, you're ready for the match task.
We Do
We Do: Pick the Matchday Line-up ⚽
Every structure has a job on the team. Drag each one onto the role it plays. Correct picks snap in and lock green; a wrong drop bounces back gently. Name all 7 for the full-time whistle! 🎉
Matched: 0/7
Drag a structure ↓ onto its matching job
🌬️ Trachea
🫧 Alveoli
🦴 Ribs
🌿 Bronchioles
🧴 Pleural membranes
🔀 Bronchi
💪 Intercostal muscles
dropMain tube (windpipe) that draws air into the lungs
dropTiny air sacs where gas exchange happens
dropTrachea splits into two of these, one per lung
dropBones that protect the thorax
dropSmaller tubes that branch off the bronchi
dropLubricate the lungs during breathing
dropMuscles between the ribs (internal & external)
Independent Work
Commentary Relay – Be the Pundit 🎙️
No worksheets — you talk. Round the room: each person picks a structure and commentates what it is and its job (like Match of the Day). Use the sentence stem on screen if you need it. TA ticks you off live as you go — that's today's evidence.
Commentary Relay Timer
08:00
🎙️ Commentary stems — pick your level
Warm-up: "The ____ is the ____." (name + what it is)
Main: "The ____ is where/that ____, which matters because ____." (name + job)
Top pundit: "The ____ is adapted for its job because ____." (structure → function)
⚽ Bonus commentary: Link one structure back to last night — e.g. "At altitude the players needed the alveoli's huge surface area to grab enough oxygen." Nail it = ⭐ Player of the Match.
📋 Live Evidence — streamlined
Whole class — one tap each:
tap to pick who commentates next
—
Names pull from your Cold Call roster (else the Year 10 group). Tap a name = present/absent. The 🎙️ cell cycles – → F → M → H (their commentary level). Autosaves for today — a reload won't lose it. ⭐ = Player of the Match.
Exit Ticket
Exit Ticket
Full-time whistle — 3·2·1 out loud. Books closed. Say your answers to the room (or a partner) — no writing needed. Teacher taps Reveal to check, and ticks your Exit on the Match Report. Every honest go counts.
Use a stem: “The ____ is where gas exchange happens.” · “The ____ is a muscle that changes the volume of the thorax.” · “The ribs are bones that ____ the lungs.”
Alveoli — where gas exchange happens. Diaphragm — a muscle that changes the volume of the thorax. Ribs — bones that protect the lungs and heart. Pleural membranes — make fluid that lubricates the lungs. Bronchi/bronchioles — tubes that carry air toward the alveoli.
1 One question you still have (or one thing to remember)
Your teacher will pick a few of these up next lesson (Ventilation).
Optional paper fallback:
Slide 1/9
Knowledge Organiser (L6): Structure of the Thorax
Structure
What It Is
Function
Thorax
The chest cavity
Contains the heart, lungs and associated structures.
Trachea
Windpipe – main tube
Draws air into the lungs. Held open by cartilage rings.
Bronchi
Two branches from trachea
Trachea splits into left and right bronchus, one per lung.
Bronchioles
Smaller tubes from bronchi
Branch off the bronchi, getting smaller and smaller.
Alveoli
Tiny air sacs
At the end of bronchioles. Where gas exchange happens.
Ribs / Ribcage
Bones enclosing thorax
Protect the lungs and heart.
Intercostal muscles
Muscles between ribs
External (outside) and internal (inside). Move ribs during breathing.
Diaphragm
Sheet of muscle
At the bottom of the thorax. Moves up/down to change thorax volume.
Pleural membranes
Membranes around lungs
Produce pleural fluid to lubricate lungs during breathing.
1) Write the word equation for aerobic respiration.
2) Name two things ATP provides energy for.
3) What does anaerobic produce in animals?
4) How does oxygen get from air into your blood?
Middle
1) Write the balanced symbol equation for aerobic respiration.
2) State two differences between aerobic and anaerobic.
3) Explain the oxygen debt.
4) What must the breathing system do to keep respiration going?
Higher
1) Write both anaerobic word equations (animals + yeast).
2) Explain why respiration is NOT breathing.
3) Why do muscle cells have more mitochondria?
4) Why does the breathing system need structures with large SA?
Lesson 6 Starter: Label What You Can
Label parts 1–5 on the diagram below. If you're stuck, use the Word Bank. Don't worry about getting them all – you'll complete the rest during the lesson.
Label
My answer
Hint
1
The tube air goes down
2
Two branches splitting off the main tube
3
Tiny air sacs (think bubbles)
4
The big pink organs
5
The sheet of muscle underneath
Word Bank: Alveoli, Bronchi, Diaphragm, Lungs, Trachea
1) The windpipe is also called the: A) Bronchus B) Trachea C) Alveolus D) Diaphragm
2) The trachea splits into how many bronchi? A) 1 B) 2 C) 3 D) 4
3) Where does gas exchange happen? A) Trachea B) Bronchi C) Alveoli D) Ribs
4) The diaphragm is made of: A) Bone B) Cartilage C) Muscle D) Membrane
Part B: Short Answer
5) Put these in order from largest to smallest: Alveoli, Bronchi, Bronchioles, Trachea.
6) What do the ribs do?
7) Name the membranes that surround the lungs.
Part C: Long Answer
8) Describe the pathway air takes from the trachea to where gas exchange happens. Name each structure.
Part D: Exam Question [3 marks]
9) Describe three structures found in the thorax and state the function of each. [3]
Independent Work – Middle (Grades 2–3)
Part A: Multiple Choice
1) Pleural membranes: A) Protect the heart B) Lubricate the lungs C) Make mucus D) Exchange gases
2) External intercostal muscles are on the: A) Inside of ribs B) Outside of ribs C) Bottom of thorax D) Top of lungs
3) Alveoli are found at the end of: A) Trachea B) Bronchi C) Bronchioles D) Ribs
Part B: Short Answer
4) Complete the table:
Structure
Function
Trachea
Bronchi
Alveoli
Diaphragm
Intercostal muscles
5) Name the two types of intercostal muscles and where each is found.
Part C: Long Answer
6) Explain why the thorax needs both ribs and intercostal muscles.
Part D: Exam Question [4 marks]
7) Describe the structure of the thorax. Include the airway pathway, the protective structures, and the role of the pleural membranes. [4]
Independent Work – Higher (Grades 3–5)
Part A: Multiple Choice
1) Airways branch into smaller tubes because: A) It looks nice B) It increases SA for gas exchange C) It slows air down D) It makes breathing harder
2) Intercostal muscles work antagonistically meaning: A) They fight each other B) When one contracts the other relaxes C) They both contract together D) They don't move
Part B: Short Answer
3) Explain why the airway branches into smaller and smaller tubes ending in millions of alveoli.
4) Explain the role of pleural membranes and predict what would happen without them.
Part C: Long Answer
5) Explain why the thorax needs both a ribcage for protection AND muscles that can change its volume.
Part D: Exam Question [5 marks]
6) Describe the complete structure of the thorax. For each structure, explain how it contributes to the thorax's function of getting oxygen into the blood. [5]
Exit Ticket – Foundation (U–1)
1) Put in order largest → smallest: Alveoli, Bronchi, Bronchioles, Trachea.
2) What is the diaphragm made of?
3) What do the ribs do?
Exit Ticket – Middle (2–3)
1) Name the two types of intercostal muscles and where each is found.
2) What do pleural membranes do?
3) Describe the air pathway from trachea to alveoli.
Exit Ticket – Higher (3–5)
1) Explain why the thorax needs both ribs AND intercostal muscles.
2) Why do airways branch into millions of alveoli?
3) Predict what happens if pleural membranes are damaged.
We Do – Class Evidence
🎓 TA Focus
🎯 Cold Call
—
📺 The Breathing System
Short GCSE/IGCSE clip on the structure of the respiratory system (spec 2.46). Teacher: swap the link in the code if you prefer another.
🏆 Class Progress Board
XP earned this lesson through the interactive tasks.
