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Body Lab 3-5 / Week 02 / Thursday
4/6
Week 02 · The Skeleton

Thursday

Joints let you move
// The living frame that holds you up
⏱ about 15 min

Thursday: Joints Let You Move

Rocket builds a cardboard puppet. Its arms are stiff sticks that cannot bend. "It looks so stiff!" he says.

Raven waves her arm in a big circle. "What do you notice about my arm?"

Nova hovers by Raven's shoulder. "Look where two bones meet," she says. "That is where bending happens."

Rocket grabs paper fasteners. "Joints! My puppet needs joints."

Where bones meet

A joint is a place where two bones meet.

Some joints do not move at all. The skull has joints like these.

Other joints move a lot. They let you bend, twist and turn.

Ligaments hold bones together at the joints. They are like very strong rubber bands.

Cartilage cushions the bones so they do not rub together.

Three moving joints

JointHow it movesWhere you have one
hinge jointBends one way, like a doorelbows, knees, fingers
ball-and-socket jointMoves in every directionshoulders, hips
pivot jointTwists or rotatesthe neck, to turn your head side to side

In a ball-and-socket joint, the round end of one bone fits in a cup.

Joints also have a slippery fluid. It helps them move easily.

NAME THAT JOINT
  • Read the question.
  • Tap your answer.
Your knee bends one way, like a door. What joint is it?
Your shoulder lets your arm swing in a big circle. What joint is it?
You turn your head to look left and right. What joint helps?
What do we call the place where two bones meet?
WHY THIS EXERCISEA joint is where two bones meet.
Bones are held together at joints by ____.
Bendy tissue that cushions bones is ____.
Try it
Slowly bend and straighten your elbow. Can it bend backward?
Now swing your arm slowly in a circle at the shoulder.
Which joint moved in more directions?
Safety first
Move slowly and gently.
Never push a joint farther than it wants to go.
Give yourself plenty of space.
StatementTrue or false?
Every joint in the body can move.?
Your elbow is a hinge joint.?
Your hip is a ball-and-socket joint.?
A pivot joint lets you twist.?
WHY THIS EXERCISESkull joints stay still. Hinge, ball-and-socket and pivot joints move.
WHERE IS IT?
  • Read the question.
  • Tap your answer.
Where do you have ball-and-socket joints?
Where do you have joints that do not move?
A joint that bends one way like a door: ____ joint.
A joint that twists: ____ joint.

Joint genius! Tomorrow we hunt for record-breaking bones and count bones in hands.

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