supprot animal bodies from the outside (exokeleton) mostly seen in insects or arthropods or inside (indoskeleton) of the body made of bones, seen in humans
Bones
are hard and strong, containing a lot of calcium.
if you don't have enough calcium in your diet, your bones may not grow properly.
bones contain living cells, so you also need protein in your diet to build strong bones.
Joints
bones cannot bend, so movement in skeletons can only take place where two bones meet eachother, called joints.
Hinge Joints
they work like hinges on a door and let the bones move back and forth in one direction, in the same way a door opens and closes.
Ball-and-socket Joints
let bones move in a complete circle, having one bone end in a ball like shape and the other havinga cup or socket that the ball fits into.
