1. Histology of bones
Dr Maha ELBeltagy
2018

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

3. The 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. Bone cells

5. Organization of bone tissue
compact
spongy

6. Compact vs. spongy bone Compact bone Spongy bone External layer
Arranged in osteons
Central canals connected to each other by perforating canals
Bones are heavy
Found mainly in long bones
Spongy bone
Near the center
No osteons
Arranged in trabeculae
Major type in short, flat, irregular bones
Much lighter than compact bone
Supports red bone marrow

7. Blood and nerve supply to bone
Abundant supply of blood
May have several nutrient arteries
Nerves accompany blood vessels

8. Ossification (osteogenesis)
Bone forms within mesenchyme in layers (intramembranous)
Flat bones of skull and mandible
Osteocytes secrete calcium
Compact and spongy bone form

9. Endochondral ossification
Most bones are formed this way
Calcification is triggered when chondrocytes die
Vascularization triggers ossification

10. Bone growth in length (epiphyseal plate)
Growth is on epiphyseal side
Resting cartilage secures epiphyseal plate
Dividing cells are in proliferating cartilage
Cells mature in hypertrophic cartilage
Osteoblasts replace calcified cartilage

11. Bones get thicker by appositional growth
Osteoblasts form new extracellular matrix
Blood vessel becomes enclosed, supports new osteon
Osteoblasts lay down extracellular matrix

12. Bone remodeling replaces old tissue
Resorption by osteoclasts, deposition by osteoblasts
Strengthens bone
Repairs damaged bone