Term 1G

rad

e 5

Life and living things, structures

Un

it 2

Animals and theirskeletons2.2 Joints2.2.1 Joints in the human bodyThe two most common types of joints are discussed below:Ball and socket joints Hinge joints

Animals and theirskeletons

Ball and socket joints Hinge joints

The most flexible joints. Allows bones to turn and swing in differentdirections.

The round top part of one bone fits into the cup-shaped socket of another bone.

The joint can only bend in onedirection along a straight line.

It works the same as the hinges of adoor.

Animals and theirskeletons

Ball and socket joints Hinge joints

Examples: hip joint and shoulder joint

This is why your arms and legs can swing in many directions.

Examples: elbow and knee

This is why you can bend your elbowand knee in one direction only.

Animals and theirskeletons

2.2.2 CartilageCartilage:• strong flexible substance; • softer than bone; • found on the bones at

joints;• serves as a cushion

between the two bones.

Joints

Animals and theirskeletons

Animals and theirskeletons

2.2.3 LigamentsLigaments:• are strong and

elastic; • connect the two

bones in a joint.; • hold the bones in

place.

Animals and theirskeletons2.2.4 Joints in animalsskeleton of a snake skeleton of a fish.

Animals and theirskeletonsExamples of different animals that have limbsthat are fitted to the rest of the skeleton by joints:

Animals and theirskeletons

Most mammals have four limbs.

Animals and theirskeletons

Most reptiles and amphibians also have four limbs.