Bone Structure
The structure of a bone varies depending on its size, shape and function. Bones are classified according to their shape: flat, short, long, irregular, sesamoid.
Imagine your femur as we talk about this next section on long bones.
The long central tubular section is the diaphysis. The hollow center is lined with endosteum and filled with marrow. At the end of each diaphysis is an epiphysis. The epiphysis are commonly covered with articular cartilage for protection and integral to joint movement. Articular cartilage is usually composed of hyaline cartilage. There is a thin wrap that goes around the diaphysis called the periosteum.
There are two types of structural bone. Compact is a very dense, weight-bearing bone. Spongy bone is still supportive but less dense so it is lighter weight. If we were composed of only compact bone, our weight would be much heavier, which would be a disadvantage for movement and survival.
Questions:
Name the following:
This is composed of hyaline cartilage at the end of a long bone______________________________
The end of a long bone is called the ___________________________________________________
The long central hollow portion of a long bone __________________________________________
A thin connective tissue wrap that covers and helps provides nutrients _______________________
The lighter weight bone mostly located in the epiphysis ___________________________________
A very dense type of bone mostly in the diaphysis _______________________________________
Microscopic Structure
The basic unit of compact bone is the osteon. The osteon resembles a bull’s eye target with rings that grow out from the center. In the center of the osteon is the central canal, which is also called the osteonic canal. Osteonic canals contain blood vessels and nerves that run longitudinally through the bone. In concentric circles around the osteon are small spaces called lacunae, where bone cells reside. Mature bone cells are called osteocytes, which are responsible for general maintenance of the bone. Osteocytes also help break down bone. Less mature bone cells are called osteoblasts, which are responsible for creating new bone.
Osteocytes pass gases and nutrients through small interconnections called canaliculi. Larger transverse pathways that connect two osteons together are called perforating canals. Blood vessels and nerves run transversely in the perforating canals.
Intercellular matrix is composed of collagen and inorganic salts.
Questions:
Bone cells that create and lay down bone are called ______________________________________
Mature bone cells that break down bone are called _______________________________________
Small connections within and osteon are called __________________________________________
Large transverse connections between two different osteons are called _______________________
Another name for central canal is ____________________________________________________
Bone is organized in concentric circles called an _________________________________________
T/F Osteons are common in spongy bone.
T/F The dense network of osteons create a very supportive type of bone.