Melanoma skin cancer. Cells are dead, wear off. Keratim protein produced in skin cells as they move to surface.
Hydra has opening to fluid compartment, but small opening.
Great ape - opposable thumb and big toe. Our opposable thumb allows grasping. Has blood vessel, nerve. Bone deposited around osteoblast until trapped in lacunae spaces, then cells called osteocytes. Bones remodeled throughout life.