Sharks have a skeleton composed of cartilage, not bones.
Cartilage is a type of connective tissue that grows from the mesoderm at early stages, which makes it different than bone. Cartilage has yellowish appearance and it bends in response to force. Bone forms in red blood cells called osteoblasts and the matrix formed by osteoblasts when they combine together makes material shaped like bones. Chondrocytes are cells that produce this cartilaginous substance for shark’s bodily structure and sharks do not grow new ones once they replace their old ones like humans do because sharks never stop growing
A shark skeleton has only cartilage.
Sharks have skeletons consisting of a cartilaginous endoskeleton composed of flexible cartilage rather than bone tissue. Cartilage does not fossilize as bone tissue does, so it is difficult to say which ancient animals had a cartilaginous skeleton and what their relationship to the modern descendants would be. Some paleontologists theorize that this adaptation may have developed from fish that left the oceans for fresh water environments which do not contain many nutrients needed for building strong bones out of calcium carbonate, such as sharks or rays. Since there are no hard structures in living sharks’ skeletons, they also find it easier to change shape (especially before birth)
Sharks are cartilaginous fish, which means they don’t have any bones. Sharks have hard bodies with bony plates called dermal denticles that give them a smooth shape. It is impossible to count the number of shark’s bones because they don’t actually have any more than the rest of us! In total, sharks only really have skeletons made of cartilage not bone, as a result they are sometimes called jawless fish and their skeletons consist mainly just protective plates or spines and do not contain minerals like calcium or phosphorus. Their skeleton is similar to our ear’s eardrum; an animal with no real known substantial form of protection but does serve some function in keeping attributes that help make up who it is.
