1. Osteon/Haversion System- functional unit of bone
Central (osteonic) canal - for B.V., and nerves Lamellae – sheets/layers of matrix Lacunae – space for a bone cell

2. Canaliculi – tiny interconnecting channels that allow the osteocytes to communicate w/ each other (pass waste and nutrients)
Perforating canal – allows the vessel in the osteonic canal to connect with the source blood vessel in the medullary cavity [Volkman’s]
Circumferential lamellae – layers of bone tissue just beneath the periosteum

4. Bone Growth & Development
OSSIFICATION=Formation of bone
During first eight weeks of embryonic dev’t

5. 1.Intramembranous bones – (flat bones of skull, mandible, clavicle)
A. osteoblasts cluster
B. secrete matrix which forms thin plates and becomes spongy bone
C. o‘blasts become trapped in lacunae (become o‘cytes); periosteum forms
D. o‘blasts in the periosteum form a layer of compact bone over the spongy bone

8. 2. Endochondral Bones (All but the clavicle, flat bones of skull and mandible) CHONDROCYTES-cartilage cells A. chondroblasts produce hyaline cartilage - forms the shape of the bone it will become (template) B. chondroblasts become surrounded by cartilage – now known as chondrocytes C. B.V. penetrate – bring inc. # of o’blasts, some chondros die, others turn into o’blasts.

9. D. Cartilage is destroyed, beginning in the center of diaphysis – forms primary (10) ossification center - cartilage is replaced w/ bone
E. Secondary (20) ossif. centers form in the epiphyses. Almost all cartilage is replaced with bone – some remains …
F. Artic. cart. remains on the outside of epiphyses at joint surfaces
G. Thin line of cartilage remains (epiphyseal/ growth plate) at border of epiph. and diaph.