Bone Flashcards
What is the composition of bone?
33% organic material & 67% inorganic material by dry weight
Describe the constituents of the organic material.
It constitutes the organic matrix of bone which is composed of fibers and ground substance.
The fibers are mainly collagen type 1 and constitute about 90% of the organic matrix.
The ground substance is amorphous. It is composed of non-collagenous matrix proteins (10%) such as saialoproteins, osteocalcin, osteonectin, and proteoglycans..
What is the function of non-collagenous proteins?
The play a role in:
- bone matrix mineralization
- cellular adhesion
- regulating bone activity during alternating between bone formation and resorption.
Describe the constituents of inorganic material.
It consists mainly of apatite crystals which are composed mainly of calcium and inorganic orthophosphate . These crystals are in the form of plates which are deposited on and between collagen molecules (microfibrils) and non-collagenous ground substance. The can be seen under electron microscope.
How is bone physiology controlled?
It is controlled systemically by hormones, especially parathyroid and locally by growth factors and cytokines.
Complete:
All bones are composed of a …………………….. and a ……………….. formed by a network of bone trabeculae filled with red or yellow bone marrow.
dense outer sheet of compact bone, central medullary cavity
What is the periosteum?
It is a fibrocellular vascular membrane that covers the outer surface of the bone. It consists of 2 layers :
- outer fibrous layer
- inner cellular layer
Describe the 2 layers of periosteum?
- The outer fibrous layer: consists of dense irregular connective tissue with some fibroblasts and blood vessels. It sends collagen fibers to penetrate the superficial layer of compact bone and binds the periosteum to the bone. The embedded portions of the fibers within the bone are called Sharpey’s Fibers.
- The inner cellular layer: contains progenitor cells, which can proliferate and differentiate into osteoblasts. The deeper cells of this layer close to the forming bone are the osteoblasts which produce the bone matrix.
Complete:
The cells of the periosteum communicate with each other and with osteocytes within bone by ……………… .
Gap junctions
What is the Endosteum?
It is a cellular layer of flattened osteogenic cells that lines the inner surface of the compact bone and trabeculae in the marrow cavities. They also line the Haversian canals and Volkmann’s canals.
What are types of bone?
There are two main types of bones: 1- Lamellar bone - Compact or cortical bone - Cancellous or spongy bone - Bundle bone 2- Embryonic or non-lammellar bone - Woven bone
What types of lamellae are recognized in compact bone?
There are 3 distinct types : concentric, interstitial, and circumferential lamellae
What is the Haversian canal (osteon)?
The main bulk of the compact bone is made up of concentric bony layers or concentric lamellae surrounding a central canal containing blood vessels, lymphatics and nerves. This canal is a Haversian canal which together with the surrounding lamellae forms a Haversian system or osteon.
What are Volkman’s canal?
They are horizontal or oblique channels that connect the adjacent Haversian canals to each other, the marrow cavity, and to the periosteum. The ensure a rich vascular network throught the bone.
What is the interstitial lamellae?
They are irregular lamellae, remnants of old Haversian systems created during resorption, reapposition of bone and remodeling, They are interspersed between intact Haversian systems.
