Anatomy & Histology of Bones

1. Histology of Bone

2. What is Bone:
Bone is the basic unit of skeletal system
which provides-
 Framework of the body
 Protection to vital organs
 Mechanical movement

3. Classification of Bone
Based on location: 2
Types
 Axial skeleton.
* Central axis of skeleton
* 28 skull bone
* 26 vertebrae
* 25 ribs
* 1 hyoid bone

4.  Appendicular skeleton.
* Non-axial bones of skeleton
* 64 in upper extremities
* 62 in lower extremities
Classification of Bone (cont.)

5. Based on shape:
 Flat bone: skull, vertebrae, ribs
 Tubular bone: bones in hands and feets
 Irregular bone: face and vertebral column
 Sesamoid bone: patella
 Accessory bone: bones that develop in other
ossification centre
Classification of Bone (cont.)

6. Based on size:
 Long bone: tubular in shape with a hollow
shaft.
Classification of Bone (cont.)
 Short bone: cuboidal in shape, located
in hands and feet.

7. Gross structure of bone:
 Epiphysis: Ends of a bone
 Diaphysis: Shaft of a bone
 Metaphysis: Joining of Epiphysis and
Diaphysis. This is the most vascular part of a
bone. Because most of the supplying arteries
and veins enters through this area.
 Periosteum: Outer covering of bone. This
area is pain sensitive.
 Endosteum: thin layer lining the medulary
cavity.

9. Blood and nerve supply of
Bone:
Blood: Bone has a rich vascular supply,
receiving 10-20% of total CO. major
contributing arteries are-
* Diaphyseal Nutrient artery
* Metaphyseal and Epiphysial arteries
* Periosteal arterioles
Nerves: Rich in articular extremities,
vertabrae, and flat bones. Most of the
cases nerves accompany with arteries.

10. Microscopic structure of bone:
1. Bone cell:
 Osteoprogenitor cell:
◦ Osteo = bone, pro = precursor, gen = to
produce
◦ Unspecialized cells
◦ Undergo mitosis and develop into
osteoblasts
◦ Found in: inner periosteum, endosteum,
and in canals

11.  Osteoblast:
 Cells that form bone
 Lost ability to divide
 Secretes collagen which helps build
bones
 Found on surface of bones
Microscopic structure of bone
(cont.):

12.  Osteoclast:
◦ Develop from circulating monocytes (WBC)
◦ Settles on surface of bone
◦ Function is bone resorption (destroying
matrix)
Microscopic structure of bone
(cont.):

13.  Osteocyte:
◦ Mature bone cells from osteoblasts
◦ Principal cells of bone tissue
◦ Can’t divide
◦ Maintains cellular activity
 Exchange of nutrients and waste with blood
 Calcium absorption
Microscopic structure of bone
(cont.):

14. 2. Bone matrix: Bone matrix consist of
both organic and inorganic materials.
The major constituent of matrix are-
 Type-1 collagen
 Glycos-aminoglycan
 Bi-carbonate
 Citrate
 Mg, K, P, Na
Microscopic structure of bone
(cont.):

15. 3. Haversian system: primary structural
unit of a compact bone is the
haversian system. This is usually a
few milimiteres long and 0.2mm in
diameter. This system contains-
 Haversian canal
 Volkmans canal
 blood vessel
 Bone cells
Microscopic structure of bone
(cont.):

16. Microscopic structure of bone
(cont.):

17. Microscopic structure of bone
(cont.):

18. Joints:
 Synostosis joint: Nonmovable
 Synchondrosis: joint with limited movement,
ie. Costochondral joints
 Syndesmosis: bones are joint with interrosias
membrane, ie. Tibio-fibular joint.
 Diarthrosis: joint with great mobility, ie. Knee,
shoulder etc.
Connective structure of bone:

19. Periosteum:
 Outer covering of bone
 Carries a dense network of blood, lymphatic
vessels and sensory nerve.
 Due to presence of sensory nerve
periosteum is pain sensitive.
Connective structure of bone
(cont.):

20. Endosteum:
 composed of osteoprogenitor cell
 covering of the surface of medullary cavity
and haversian canal.
Connective structure of bone
(cont.):

21. Synovium:
 Synovial membrane: smooth and
villous connective tissue.
 Consists of phagocytic and fibroblast
like cells, elastic fibers, nerve, adipose
tissue.
Meniscus
Intervertebral disc
Connective structure of bone
(cont.):