Year 8 Science
Body Systems
Revision Lesson
Six systems, one working body.
Learning intentions
We are learning to:
• Name the main organs of each body system and describe what each system
does.
Digestive
Respiratory
• Use the correct scientific terms when explaining structure and function.
• Explain how the systems work together to keep the body alive.
Circulatory
Excretory
Success criteria, I can:
• Label the key organs of all six systems.
• Match each system to its main job.
Musculoskeletal
• Give one example of two systems working together.
• Answer short-response questions using proper vocabulary.
Nervous
The six systems at a glance
Digestive
Respiratory
Circulatory
Breaks food into nutrients the body can
absorb.
Takes in oxygen and removes carbon
dioxide.
Transports oxygen, nutrients and wastes.
Excretory
Musculoskeletal
Nervous
Removes liquid waste and balances water.
Supports the body and lets it move.
Detects change and coordinates
responses.
Warm-up: brain dump
On your own (3 min)
Then with a partner (2 min)
• List every organ you can remember in one minute.
• Compare lists and add any organs you missed.
• Next to each one, write which system it belongs to.
• Agree on one job for each of the six systems.
• Circle any organ you are unsure about.
• Be ready to share one organ your partner forgot.
• Star the system you feel most confident on.
Share back: cold-call two pairs before moving on.
Digestive system
Its job: Breaks food down into small nutrients so the body can absorb them for energy, growth and repair.
Key structures
Must-know terms
• Mouth, oesophagus, stomach
• Mechanical vs chemical digestion
• Small intestine (most absorption)
• Enzymes speed up chemical digestion
• Large intestine (water absorbed, waste formed)
• Absorption of nutrients into blood
• Liver and pancreas help digestion
• Villi increase surface area in the small intestine
Quick check
Where are most nutrients absorbed into the blood?
Respiratory system
Its job: Brings oxygen into the body and removes carbon dioxide. This is called gas exchange.
Key structures
Must-know terms
• Nose and mouth, trachea (windpipe)
• Gas exchange happens in the alveoli
• Bronchi branching into the lungs
• Oxygen in, carbon dioxide out
• Alveoli (tiny air sacs)
• Diaphragm moves to inhale and exhale
• Diaphragm (muscle below the lungs)
• Alveoli are thin and moist for fast exchange
Quick check
In which structures does gas exchange actually take place?
Circulatory system
Its job: Transports oxygen, nutrients, wastes, hormones and heat around the whole body.
Key structures
Must-know terms
• Heart (the pump)
• Red blood cells carry oxygen
• Arteries carry blood away from the heart
• Capillaries are one cell thick
• Veins return blood to the heart
• Double circulation: lungs then body
• Capillaries (thin walls for exchange)
• Blood also carries carbon dioxide away
Quick check
Which blood vessels have walls thin enough for exchange with cells?
Excretory system
Its job: Removes liquid wastes such as urea and controls the body’s water and salt balance.
Key structures
Must-know terms
• Kidneys (filter the blood)
• Filtration of waste from blood
• Ureters (tubes to the bladder)
• Urea is a nitrogen waste
• Bladder (stores urine)
• Urine = water + dissolved wastes
• Urethra (urine leaves the body)
• Kidneys balance water in the body
Quick check
Which organ filters wastes out of the blood?
Musculoskeletal system
Its job: Supports the body, protects organs and allows movement. Muscles pull on bones to move them.
Key structures
Must-know terms
• Bones and the skeleton
• Tendons attach muscle to bone
• Joints (where bones meet)
• Ligaments attach bone to bone
• Muscles attached across joints
• Antagonistic pairs (biceps and triceps)
• Tendons and ligaments
• Muscles can only pull, not push
Quick check
What type of tissue connects a muscle to a bone?
Nervous system
Its job: Detects changes (stimuli), sends fast electrical messages and coordinates the body’s responses.
Key structures
Must-know terms
• Brain and spinal cord (central nervous system)
• Stimulus leads to a response
• Nerves reaching the whole body
• CNS = brain + spinal cord
• Neurons (nerve cells)
• Messages travel as electrical signals
• Sense organs detect stimuli
• A reflex is a fast, automatic response
Quick check
Which two organs make up the central nervous system?
How the systems work together
Getting energy to a muscle cell takes several systems at once:
→
Oxygen breathed in at the
alveoli.
→
Food broken down into
glucose.
→
Blood carries oxygen +
glucose to the cell.
Cell releases energy; the
muscle contracts.
And the wastes? The blood carries carbon dioxide back to the lungs to breathe out, and carries urea to the kidneys to remove in
urine. The nervous system fires the whole time to tell the muscle when to act.
Watch out: common traps
✗
Myth: We breathe out only carbon dioxide.
✗
Myth: Digestion is finished in the stomach.
✗
Myth: Arteries always carry oxygen-rich blood.
✗
Myth: Muscles push bones into place.
Actually: Exhaled air is mostly nitrogen and still has oxygen. Only a small amount of gas swaps over.
Actually: Most nutrients are absorbed later, in the small intestine.
Actually: Usually true, but the pulmonary artery carries oxygen-poor blood to the lungs.
Actually: Muscles can only pull. They work in antagonistic pairs to move a joint both ways.
Practice questions
Answer in your book. Use full scientific terms.
Multiple choice
Short response
1. Most nutrient absorption happens in the:
A) stomach B) small intestine
C) large intestine D) liver
• 4. Name the three types of blood vessel and give one feature
of each.
2. The main job of the respiratory system is to:
A) pump blood B) exchange gases
C) filter blood D) digest food
3. Which connects bone to bone?
A) tendon B) ligament
C) cartilage D) nerve
• 5. Explain how the respiratory and circulatory systems work
together to get oxygen to a muscle cell.
• 6. Describe what happens in a simple reflex, from stimulus
to response.
Rapid-fire round
Hands up or whiteboards. One word answers.
1
Organ that filters the blood?
6
What connects muscle to bone?
2
Tiny air sacs in the lungs?
7
CNS = brain + what?
3
Muscle that helps you breathe?
8
Waste removed by the kidneys?
4
Vessels that carry blood away from the heart?
9
Cells that carry oxygen?
5
Where does chemical digestion begin?
10
Muscle pair that bends and straightens the arm?
Exit ticket: 3 - 2 - 1
On a slip of paper before you leave:
3
systems you can explain the job of, without notes.
2
scientific terms you want to lock in before the test.
1
question you still have about how the body works.