Movement Machine Slides
Grade 3 Science • Indiana Standards
Living Systems & Movement
The Movement Machine
Discover how bones, joints, and muscles team up to protect your body and power every move you make!
Mission 1
Protect Organs
Mission 2
Bend at Joints
Mission 3
Power Movement
Skeletal System Overview
The 3 Big Jobs of Your 206 Bones
Job Breakdown
1. Support & Shape
Bones act like the wooden frame of a house. Without them, you would be floppy like a jellyfish!
💡 Keeps you standing upright
2. Protection
Hard outer bone forms armor around your softest, most vital internal organs.
💡 Brain, heart & lungs stay safe
3. Movement
Bones act as solid levers. When muscles pull on them, your whole body jumps, walks, and writes!
💡 Powered by muscles & joints
⭐ Fun Fact: An adult body has 206 bones, but you were born with about 300! Bones fuse together as you grow
Skeletal Protection
Nature's Built-In Helmets & Shields
Armor Check
The Cranium (Skull)
Your Natural Helmet
The skull is made of multiple curved bones tightly locked together. It shields your brain from bumps and falls.
🧠
Protects: Brain, eyes, and inner ears.
The Rib Cage
Your Chest Cage
12 pairs of curved rib bones form a flexible protective cage that expands when you inhale and guards your vital core organs.
❤️
Protects: Heart, lungs, and liver.
TRY IT!
Gently tap the top of your head with your fingertips. Feel how solid and hard your skull is! Take a deep breath and feel your ribs expand.
The Movement Team
How We Move: The Dynamic Trio
Teamwork
1. Bones
The Levers
Bones give structure and a solid surface for muscles to hold onto.
2. Joints
The Pivot Points
The places where two bones meet so parts can bend, rotate, and hinge.
3. Muscles
The Motors
Tissues that tighten and shorten (contract) to pull bones into action!
Bone (Lever) + Joint (Hinge) + Muscle (Pull) = Full Movement!
Joint Fundamentals
What Exactly Is a Joint?
Meeting Points
The Definition
A joint is any place in your body where two or more bones connect.
Without joints, your skeleton would be one giant, rigid stick. You couldn't sit, wave, chew, or walk!
Cartilage Cushion: A smooth, rubbery layer coats the bone ends so they glide smoothly without grinding!
Imagine If...
Imagine if your arms had no elbow joints!
- How would you eat an apple?
- How would you brush your teeth?
- How would you put on a backpack?
👉 Joints give us the flexibility to do everyday tasks!
✋ Count how many joints are in just one finger! (Hint: Look at the creases) Answer: 3 joints per finger!
Joint Type #1
Hinge Joints: Back and Forth
1-Direction Movement
Like a Door Hinge
Opens & Closes in One Direction
Just like a door swings open and closed on its metal hinge, a hinge joint allows bones to swing back and forth in one direction.
Elbows
Bends forearm up/down
Knees
Bends lower leg back
Key Characteristics
- Very strong and stable for lifting and kicking.
- Does not twist all the way around.
Classroom Action
Bend your elbow like you are lifting a book. Notice how it only bends one way and stops!
Found in: Elbows, Knees, and Finger knuckles!
Joint Type #2
Ball-and-Socket: All-Around Motion
360° Rotation
Ball Fits in a Cup
Maximum Freedom of Movement
The rounded end of one bone (the ball) fits snugly inside a cup-shaped hollow (the socket) of another bone.
Shoulders
Widest range in body
Hips
Deep socket for weight
Why We Need It
- Allows full circles, side-to-side, and up/down movement.
- Essential for swimming, throwing baseballs, and dancing.
Classroom Action: Windmill
Make a slow circle with your arm in the air. Feel your shoulder rotate all the way around!
💡 Hinge = 1 direction (door) | ⚽ Ball-and-Socket = All directions (joystick)
The Engine of Motion
Muscles ONLY Pull — They Never Push!
Muscle Pairs
Bending Your Arm
Lift
When you bend your elbow to show your muscles:
💪 Bicep contracts (shortens & bunches up) to pull forearm up.
😴 Tricep relaxes (stretches out).
Straightening Your Arm
Extend
To straighten your arm back out:
🦾 Tricep contracts (on the back of arm) to pull arm straight!
😴 Bicep relaxes.
KEY RULE
Muscles work in opposing pairs because they can only pull in one direction!
Pull + Relax = Move
Bone Health & Safety
Fueling Your Skeletal Framework
Healthy Habits
Calcium & Vitamin D
Calcium hardens your bone matrix. Vitamin D helps your body absorb it.
🥛 Milk, yogurt, broccoli & sunshine
Active Play
Running, jumping, and dancing signal your bones to grow denser and stronger!
🏃 Jump rope, tag, soccer & gymnastics
Safety Gear
Helmets protect your cranium; knee and wrist guards protect your delicate joints.
🚲 Helmets on bikes, scooters & skates
✨ Your bones are living organs that constantly rebuild and repair themselves every single day!
Classroom Showdown
Movement Machine Quick Quiz!
3 Quick Checks
Question 1
Which type of joint allows your knee to bend back and forth like a door?
Answer: Hinge Joint
Question 2
Do muscles push bones, pull bones, or do both?
Answer: Muscles ONLY pull!
Question 3
What vital organ does your cranium (skull) protect from injury?
Answer: Your Brain
🎉
You are now official Skeletal System Movement Experts!
Ready for Action!
