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๐ฌ Think about it
Swing your arm in a full circle.
Almost no other joint lets you do that.
What kind of joint gives the shoulder such freedom?
Let us see.
What is a ball and socket joint?
๐๏ธ GIF placeholder โ animation of the shoulder rotating in all directions at the ball and socket joint
Ball and Socket Joint
Ball
the rounded top of the upper arm bone
Socket
the hollow of the shoulder bone
โ
A joint allowing forward, backward, sideways and circular movement โ as at the shoulder.
| Feature | Description |
|---|---|
| How it fits | Rounded top of the upper arm bone fits a hollow of the shoulder bone |
| Movement allowed | Forward, backward, sideways and circular movement |
| Example in body | The shoulder; shoulder and collarbone form the shoulder girdle |
- The rounded top of the upper arm bone fits into a hollow of the shoulder bone.
- This forms the ball and socket joint.
- It allows forward, backward, sideways and circular movement.
- The shoulder and collarbone form the shoulder girdle.
![3.5.1 Ball and socket joint - Tissues in Action - [Teachoo] - Concepts](https://cdn.teachoo.com/19d9353f-693b-4165-8065-6cbaa868bce5/ball-and-socket-joint-shoulder-.webp)
Rounded head
of arm bone (ball)
Hollow socket
of shoulder bone
โ_โe Moves inall
directions
Shoulder girdle
(shoulder +
collarbone)
Important Points
- A ball and socket joint has a rounded bone fitting into a hollow.
- It allows movement in all directions.
- The shoulder is a ball and socket joint.
โ Test Yourself
-
Which joint allows the arm to move in all directions?
View Answer
The ball and socket joint. -
Where is a ball and socket joint found?
View Answer
At the shoulder (and the hip).
Important Definitions
- Ball and socket joint โ a joint where a rounded bone fits into a hollow, allowing movement in all directions.
