Bones have a hard coating to protect the nerves, marrow and blood vessels located in the cavity,
Spiders do not have bones. They are arthropods, their soft tissues are contained inside a hard external coating called an exoskeleton.
soft you can bend and hard you can not
Seal's bones are hard.
Calcium makes bones and teeth strong as it is like the enamel coating your teeth and bones.
Periosteum
Spiders do not have bones. They have exoskeletons which is a hard outer shell.
Mainly Diatoms
Hard.
Yes bones are as hard as rock they can take up to 1,000 pounds of pressure
The coating that goes over human bones is called periosteum. It is a dense layer of vascular connective tissue that envelops the bones, except at the surfaces of the joints. The periosteum plays a crucial role in bone growth, repair, and the attachment of muscles and tendons, as it contains nerves and blood vessels that nourish the bone.
They have an endoskeleton. The prefix exo- means external and the prefix endo- means inside. Frogs are vertebrates which means they have an internal skeletal system with bones and a backbone, they do not have a shell like a snail on the outside without bones on the inside. They do not have a hard coating on the outside instead of bones like an insect does.
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