red marrow - myeloid (blood producing) tissue found in the spaces in the spongy bone, produces both red and white blood cells. Red marrow does not increase in proportion to bone growth, and in the adult much of the red marrow changes to yellow (fatty) marrow, especially in the medullary canal.
	yellow marrow - Consists mostly of fat cells. It can revert to red marrow under extreme hematopoietic stress, such as in blood loss.
	periosteum - a fibrous covering of bones which connects to tendons and ligaments and anchors blood vessels and nerves. The inner layer of the periosteum contains osteoprogenitor cells, derived from mesenchyme cells, these are the cells which divide to become osteoblasts under appropriate stimuli. An extremely strong connection is formed with tendons and ligaments because the collagen fibers from these structures, called Sharpey's fibers, extend at an angle into the bone where they are continuous with collagen fibers in its extracellular matrix.
	endosteum - fibrous tissue lining the medullary canal. Often only once cells thick its cells are also osteoprogenitor cells.
	medullary canal - central canal of a long bone. It makes the bone lighter and in adults contains yellow marrow.
	articular cartilage - hyaline cartilage which forms part of synovial joints.