The endosteum is the thin membrane which lines the medullary cavity.
The medullary cavity is the innermost or central cavity of the bone shaft red and yellow bone marrow is stored and hence it is also called the marrow cavity.
It is located in the main shaft of long bone or the diaphysis and consists of compact bone.
The walls of the medullary cavity composed of spongy bone and has thin lining of vascular membrane called endosteum.
Medullary cavity is present inside all the bones mostly and holds the bone marrow.
