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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.