Our skeletal system is a vital organ system, yes it is actually alive itself! It keeps our other vital organs safe, makes locomotion possible, manufactures blood and handles its own repair and maintenance.
There are three types of skeletal system; Hydrostatic skeletons are found in jellyfish and worms, exoskeletons are found on insects (made of chitin) and molluscs (made of calcium carbonate), and finally, the most successful is the endosekelton, found in us and many other animals.
The endoskeleton can support more mass, and allows for more room to grow, most importantly, we don’t have need molt such as most molluscs do, so it doesn’t leave us vulnerable to predators.
Humans have 206 bones in our skeletal system, not including our teeth, and through the study of osteology we have found they begin as cartilage and are made of a third calcium phosphate to two thirds Collagen. With this incredible bone matrix it’s no wonder we are so successful.
From Crash Course: Biology on YouTube presented by Hank Green.