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.

[1][2] This area is involved in the formation of red blood cells and white blood cells, and the calcium supply for bird eggshells.

[3] Intramedullary is a medical term meaning the inside of a bone.

Examples include intramedullary rods used to treat bone fractures in orthopedic surgery and intramedullary tumors occurring in some forms of cancer or benign tumors such as an enchondroma.

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