1. Histology of Bones Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

2. (osteo= bone, genic= forming).
Connective tissue
Cells
Ground substances
1- Osteogenic
(osteo= bone, genic= forming).
2- Osteoblasts
(blast= seed).
3-Osteocytes
(cyte= cell).
4-Osteoclasts
(clast = broken).
Fibers
Mostly of Calcium and Phosphorus in the form of Hydroxyapatite crystals, responsible about Hardness of bone
Collagen
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

3. Bone cells 1- Osteoprogenitor cells
Found in the inner cellular layer of periosteum, the endosteum.
Have the ability to begin mitotic division.
Can differentiate into Osteoblasts.
Most active during bone growth and repair.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

4. 2- Osteoblasts Located on surface of bone.
Synthesize collagen fibers and can initiate calcification, called
Bone-building cells.
Imprisoned inside the matrix they secrete inside spaces called Lacunae and become Osteocytes.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

5. Do not undergo cell division.
3- Osteocytes
Mature bone cells derived from osteoblasts and housed in lacunae inside calcified matrix.
Do not undergo cell division.
Adjacent osteocytes contacted via cytoplasmic processes inside canaliculi that radiate in all directions.
Actively involved in Maintenance of matrix.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

6. Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

7. Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

8. 4-Osteoclasts
Multinucleated giant cells that originates from BM and involved in the resorption and remodeling of bone tissue.
Concentrated in the endosteum.
They releases lysosomal
enzymes and acids that dissolve the underlying matrix.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

9. Bone Tissue Components: Endosteum: Periosteum: Osseous tissue.
A membrane that covers external surface of bone.
Endosteum:
A membrane that lines cavities within bone.
Red and yellow bone marrow.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

10. Endosteum Thin membrane that lines bone cavities.
Contains monolayer of osteogenic cells.
Functions:
Nutrition of bone.
Provider of a continuous supply of osteoblasts for bone growth or repair.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

11. fibrous dense irregular connective tissue
Periosteum
Periosteum: double-layered membrane on external surface of bones
Outer layer:
Inner layer
fibrous dense irregular connective tissue
osteogenic stem cells that differentiate (specialize) into bone cells like osteoblasts (bone forming) or osteoclasts (bone dissolving) cells
protective

12. Organization of bone tissue
compact
spongy
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

13. 1. Compact bone About 80% of the whole skeleton.
Form external layer of all bones.
The basic unit of compact bone arranged in units called Osteons (Haversian system).
Their central canal runs longitudinal & lines by endosteum.
A transverse Volkmann's canals interconnects the osteons, periosteum and endosteum together. Osteons are aligned in the direction along lines of stress.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

14. 2- Spongy bone About 20% of the whole skeleton.
Consist of irregular network of trabeculae (= little beams) with numerous spaces in between filled with bone marrow.
No Haversian system.
Contain osteocytes within lacunae that nourished by diffusion from bone marrow.
Trabeculae are precisely oriented along lines of stress and located where stresses applied from many directions.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

15. Parts of a long bone Diaphysis-shaft Epiphyses- ends
Come together at metaphyses
Articular cartilage protects epiphyses
Periosteum covers bone
Medullary cavity contains marrow; is lined by endosteum
4/23/2019
Dr.Amjad Shatarat MD, PhD The University of Jordan

16. Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

17. Ossification (osteogenesis)
1-Intramembranous Bone develops from fibrous membrane
For example, Flat bones of skull and mandible
2-Osteocytes secrete calcium
Compact and spongy bone form
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

18. Endochondral ossification
Bone develops from hyaline cartilage
Most bones are formed this way
Calcification is triggered when chondrocytes die
Vascularization triggers ossification
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

19. Bone growth in length (epiphyseal plate)
Growth is on epiphyseal side
Resting cartilage secures
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

20. Bones get thicker? Periosteum
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

21. Bone remodeling replaces old tissue (destroyed and reformed)
Bone is Dynamic
Bone remodeling replaces old tissue (destroyed and reformed)
Coupled process between:
Bone deposition (by osteoblasts)
Bone destruction/resorption (by osteoclasts)
5-7% of bone mass recycled weekly
All spongy bone replaced every 3-4 years.
All compact bone replaced every 10 years.
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

22. Wolff’s law Life style and bone formation
Why is exercise good for bones?
Wolff’s law
Bones respond to muscles pulling on them (mechanical stress) and to gravity by keeping the bones strong where they are being stressed.
Therefore, an active life style will enhance the bone formation
Dr.Amjad Shatarat MD, PhD The University of Jordan
4/23/2019

23. How does aging affect bones?
Loss of bone mass due to calcium loss
Decreased production of collagen
4/23/2019
Dr.Amjad Shatarat MD, PhD The University of Jordan