| A | B |
|---|
| Axial skeleton | the portion of the skeleton that supports and protects the head, neck, and trunk |
| appendicular skeleton | the portion of the skeleton that attaches to the axial skeleton and has the limbs attached to it |
| exoskeleton | a body covering, typically made of chitin, that provides support and protection |
| symbiosis | a close relationship between two or more species where at least one benefits |
| smooth muscles | involuntary muscles |
| skeletal muscles | voluntary muscles |
| keratinization | process by which cells are hardened and die in order to make hair, nails, and the other layer of skin |
| bone marrow | makes blood cells |
| collagen | makes bones flexible |
| minerals | makes bones hard |
| arthropods | animals with exoskeletons |
| ligament | holds bones together in a joint |
| cartilage | cushions the bones in a joint so they do not rub together painfully |
| tendon | connects skeletal muscles to the skeleton |
