Library · Anatomy
Medullary cavity of bone
Make it clearer
Long bones are not solid. Inside they have a space that runs along their length, the medullary cavity, and that space is in the diaphysis, the elongated middle part of the bone. What lives in there is the bone marrow.
The wall of that cavity is not bare. It is lined by the endosteum, a very thin membrane that also lines the Haversian canals, small channels inside the bone, and all the other internal cavities. The endosteum contains osteoprogenitor cells, reserves that can turn into the cells that build bone.
And not all marrow is the same or in the same place. In a long bone, the space in the diaphysis holds yellow marrow. Red marrow, where red blood cells are formed, is concentrated in the epiphysis, the widened end of the bone.
A long bone is therefore a hollow tube: the wall carries the weight and the center is left free for something else. It is the same reason a steel tube weighs less than a solid bar and holds up almost as well.
In brief
The medullary cavity is the space that runs inside the diaphysis, the long part of the bone, and it houses the bone marrow.
A hollow tube, with the wall bearing the load and the center left open.
It is lined by the endosteum, a thin membrane with osteoprogenitor cells that also lines the Haversian canals and the other internal cavities of bone.
In a long bone the diaphysis holds yellow marrow, while red marrow, where red blood cells are formed, is concentrated in the epiphysis.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingAnatomy, Bones, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingHistology, Periosteum And Endosteum, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated