Marrow cavity
Also called: medullary cavity, bone marrow cavity
What it means
The marrow cavity is the hollow, central space inside a long bone that holds bone marrow.
Changes in the marrow cavity and the cortical bone around it affect how strong your bones stay as you age.
The marrow cavity, also called the medullary cavity, is the hollow space that runs through the center of a long bone, like the femur or humerus. In adults it's mostly filled with yellow marrow, which is rich in fat cells, though red marrow (where blood cells are made) is found in certain areas like the ends of long bones and flat bones.
This cavity is lined by a thin layer of tissue called the endosteum, which plays a role in bone remodeling, the constant process of breaking down and rebuilding bone. The marrow cavity itself isn't 'active' bone tissue, but it sits right next to the inner cortical bone surface, where a lot of resorption and rebuilding happens over a lifetime.
You won't see this term on a bone density report, but it's part of the basic architecture of every long bone. As bones age or lose density, the cortical shell around the marrow cavity can thin, which is one reason bone strength and fracture risk change over time.
The hollow marrow cavity and the cortical bone around it together affect how strong your bones stay.
Where this leads
WordWondering what actually fills that hollow cavity? Bone marrow is the soft tissue inside that makes your blood cells.
Related words
Bone marrow is the soft tissue inside bones where red bone marrow makes your red blood cells, white blood cells, and…
Yellow bone marrow is the soft, fatty tissue found mostly in the hollow centers of long bones, as opposed to red…
The endosteum is the thin layer of cells lining the inner surface of bone, next to the marrow cavity.
Cortical bone is the dense, hard outer layer of bone that forms a protective shell and resists bending and twisting…
The diaphysis is the long middle shaft of a long bone, such as the femur or humerus, made mostly of dense cortical…
Endosteal resorption is the thinning of bone from the inner surface outward, which widens the hollow space inside…
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