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Located in the main shaft of a long bone (consisting mostly of compact bone), the medullary cavity has walls composed of spongy bone (cancellous bone) and is lined with a thin, vascular membrane . [1] [2] This area is involved in the formation of red blood cells and white blood cells, and the calcium supply for bird eggshells. The area has been ...
The endosteum (pl.: endostea) is a thin vascular membrane of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones. [1] [2] This endosteal surface is usually resorbed during long periods of malnutrition, resulting in less cortical thickness. [citation needed]
Beneath the cortical bone layer is a layer of spongy cancellous bone. Inside this is the medullary cavity which has an inner core of bone marrow, it contains nutrients and help in formation of cells, made up of yellow marrow in the adult and red marrow in the child.
The cortex of a bone is used to refer to its outer layers, and medulla used to refer to the inner surface of the bone. Red marrow, in which blood is formed is present in spongy bone as well as in the medullary cavity, while the fatty yellow marrow is present primarily in the medullary cavity. [citation needed]
The ulna is a long bone. The long, narrow medullary cavity of the ulna is enclosed in a strong wall of cortical tissue which is thickest along the interosseous border and dorsal surface. At the extremities the compact layer thins. The compact layer is continued onto the back of the olecranon as a plate of close spongy bone with lamellae parallel.
Bone marrow comprises approximately 5% of total body mass in healthy adult humans, such that a man weighing 73 kg (161 lbs) will have around 3.7 kg (8 lbs) of bone marrow. [5] Human marrow produces approximately 500 billion blood cells per day, which join the systemic circulation via permeable vasculature sinusoids within the medullary cavity. [6]
Diagram of a typical long bone showing both compact (cortical) and cancellous (spongy) bone. Osteons on cross-section of a bone. In osteology, the osteon or haversian system (/ h ə ˈ v ɜːr. ʒ ən /; named for Clopton Havers) is the fundamental functional unit of much compact bone.
The medial lemniscus, also known as Reil's band or Reil's ribbon (for German anatomist Johann Christian Reil), is a large ascending bundle of heavily myelinated axons that decussate in the brainstem, specifically in the medulla oblongata.