Biology revision 1- Structure of the human body

The human skeleton contains 206 bones
Bones allow us to move, support and protect us
Bones are hollow, and contain marrow, which makes red blood cells
Invertebrates have no backbone, but a tough exoskeleton
1. Invertebrates have a backbone and internal skeletons called endoskeletons
Bones are light and strong
Muscles always work in pairs called antagonistic pairs.
Muscles are attatched to bones by cords called tendons
Muscles contain the movements of the joints
Muscles contract and expand to move joints
Types of joints are-hinge joints, knee joints, hip joints and ball and socket joints.
1. Knee joints are in the knee (obviously) and are not very special
2. HIinge joints only bend in one direction
3. Ball and socket joints allow twisting and bending
4. Hip joints also have no special features
5. Fixed joints are in the skull, where bones meet but there is no movement

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