Rørknogle

Rørknogle is a Danish term that translates to "hollow bone" or "pipe bone" in English. In anatomical contexts, it refers to the long bones of the limbs, such as the femur (thigh bone) and humerus (upper arm bone). These bones are characterized by their cylindrical shape, which is formed by a shaft containing a hollow medullary cavity.

The structure of a rørknogle is adapted for weight-bearing and locomotion. The outer layer is composed of dense, compact bone, providing strength and rigidity. Inside this is spongy bone, which is less dense and contains red bone marrow responsible for blood cell production. The medullary cavity, a central canal within the bone, also houses bone marrow, which can be red or yellow depending on the age of the individual and the specific bone.

The hollow nature of these bones offers a significant advantage in terms of weight reduction without compromising structural integrity. This is particularly important for animals that need to move efficiently. In birds, for example, rørknogle are even more specialized, often being pneumatized, meaning they contain air sacs that further reduce weight for flight. The term is primarily used in zoology and comparative anatomy to describe this common skeletal feature across various vertebrate species.