What is the structure of a typical long bone?
The major parts of a long bone are: epiphysis, epiphyseal plate, metaphysis, diaphysis, medullary cavity, articular cartilage, and periosteum.
Epiphysis—From the Greek, meaning “to grow upon,” this spongy bone tissue is spherical in shape and is located at both the distal and proximal end of a long bone.
Epiphyseal plate—This is a layer of hyaline cartilage between the epiphysis and metaphysis. It is the location where bones continue to grow after birth and is therefore often referred to as the epiphyseal growth plate.
Metaphysis—From the Greek meta, meaning “between,” this is the area of the bone between the epiphysis and diaphysis.
Diaphysis—From the Greek, meaning “to grow between,” the diaphysis is the long, cylindrical, hollow shaft of the bone.
Medullary cavity—From the Latin word meaning “marrow,” it is the area within the diaphysis and contains fatty (mostly adipose) yellow marrow in adults.
Articular cartilage—A thin layer of hyaline cartilage covering the epiphysis where the bone joins another bone. It helps to reduce friction during joint movement and allows the bones to glide past one another.
Periosteum—From the Greek peri, meaning “around,” and osteon, meaning “bone,” it is a white, tough, fibrous membrane that covers the outer surface of the bone whenever it is not covered by articular cartilage. It contains nerves, lymphatic vessels, and blood vessels that provide nutrients to the bone.