The endosteum (plural endostea) is a thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the

medullary cavity The medullary cavity (''medulla'', innermost part) is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow ( adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity. Located in the m ...

of long

bone A bone is a Stiffness, rigid Organ (biology), organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red blood cell, red and white blood cells, store minerals, provid ...

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 ...

, 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 Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

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. Endosteum lines the inner surface of the medullary cavity of all long bones. Structu ...

, or the periosteal surface. During

bone growth Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

, the width of the bone increases as

osteoblasts Osteoblasts (from the Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts function ...

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 prote ...

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