The endosteum (: endostea) is a thin vascular membrane of

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

that lines the inner surface of the bony tissue that forms the medullary cavity of long

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

s. This endosteal surface is usually resorbed during long periods of

malnutrition Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is a deficiency, excess, or imbalance of energy, protein and other nutrients which adversely affects the body's tissues a ...

, resulting in less cortical thickness. The outer surface of a bone is lined by a thin layer of connective tissue that is very similar in morphology and function to endosteum. It is called the

periosteum The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. (At the joints of long bones the bone's outer surface is lined with "articular cartila ...

, or the periosteal surface. During bone growth, the width of the bone increases as osteoblasts lay new bone tissue at the periosteum. To prevent the bone from becoming unnecessarily thick,

osteoclasts An osteoclast () is a type of bone cell that breaks down bone tissue. This function is critical in the maintenance, repair, and remodeling of bones of the vertebral skeleton. The osteoclast disassembles and digests the composite of hydrated ...

resorb the bone from the endosteal side.

Additional images

File:Illu long bone.jpg , Long bone

References

External links

* – "Bone, structure (LM, High)"
Image at dal.ca
Musculoskeletal system {{musculoskeletal-stub