1. Bone Structure

2. Bone Structure in General
Bone is a type of connective tissue
It is as strong as steel but as light as aluminum
It is a moist living tissue that constantly breaks down and rebuilds itself
Each bone adjusts its shape and size during the growing process, after injury, and in response to stress
A bone’s shape makes possible its functions
Bony projections called processes provides sites of attachment for ligaments and tendons
Grooves and openings are passageways for blood vessels and nerves

3. Parts of a Long Bone Long bones are divided into three regions
Epiphysis
Metaphysis
Diaphysis

4. Epiphysis Is the expanded portion at the end of each long bone
It forms a joint (articulates) with another bone
The proximal epiphysis is the end nearest the torso
The distal epiphysis is the end farthest from the torso
The outer surface of the epiphysis is covered with a layer of hyaline cartilage called articular cartilage

5. Diaphysis & Metaphysis
The diaphysis is the shaft of the long bone
The metaphysis is the widening part of the bone between the epiphysis and diaphysis

6. Internal Long Bone Structure
Long bone consists of a porous central cavity surrounded by a ring of dense material
The layers from the outside to the inside of bone are:
Periosteum
Compact bone
Spongy bone
Medullary cavity
Endosteum
Marrow

7. Periosteum Is a tough membrane that covers the surface of the bone
It doesn’t cover the articular cartilage on its ends
It contains a network of blood vessels and nerves, which supply nutrients and signal pain

8. Compact Bone
Is a hard thick layered material that enables bone to endure large amounts of stress
It makes up the wall of the diaphysis
It is also known as cortical bone
Its extracellular matrix is continuous with no gaps

9. Spongy Bone Composes mainly the epiphysis of bone
It is also known as cancellous bone
It consists of many branching bony plates called trabeculae
Irregular connecting spaces between the trabeculae help reduce the bone’s weight
The bony plates are most highly developed in the regions of the epiphyses subjected to compressive forces

10. Medullary Cavity, Endosteum, & Marrow
In the diaphysis, compact bone forms a semi-rigid tube with a hallow chamber called the medullary cavity
This cavity is continuous with the spaces of spongy bone
A thin membrane containing bone-forming cells, called the endosteum lines it
A specialized connective tissue known as marrow, fills it
Marrow comes in two forms red & yellow

11. Internal Long Bone Structure

12. Microscopic Structure of Compact Bone
Compact bone is composed of cylinders of mineral crystals and protein fibers called lamellae
In the center of each lamellae is a narrow channel called a Haversian canal
Blood vessels run through interconnected Haversian canals, supplying nourishment to the bone tissue
Wrapped around each Haversian canal are layers of protein fibers
Haversian canals are connected to each other via Volkmann’s canals, which carry a blood vessel, nerve, and lymph vessel

13. Microscopic Structure of Compact Bone
Embedded within the large gaps between the protein layers are bone cells, known as osteocytes
Each osteocyte is embedded in fluid filled cavities called, lacunae and surrounded by concentric layers of bone matrix, lamellae
The lamellae and lacunae together form an osteon
The lacunae are connected to one another and to Haversian canals by a system of interconnecting canals called canaliculi

14. Internal Bone Structure