Osteocytes

Mature bone cells that cannot divide

Most numerous bone cell type

Maintain protein and mineral content of adjacent matrix

• Located where bones not heavily stressed or in many directions
• Lamellae form struts and plates, creating an open network

- Reduces weight of skeleton

- No blood vessels in matrix

Femur Surface Features

• trochanter
• head
• neck
• diaphysis
• facet
• condyle 

Periosteum

Has two layers

1. Fibrous outer layer
2. Cellular inner layer

Functions:

1. isolate bone form surrounding tissues
2. route for bloos nd nervous supply
3. actively participate in a bone growth and repair

Steps of Intrarmembranous Ossification

1. Mesenchymal cells secerte osteoid matrix
2. osteoid matrix becomes mineralized
3. bone grows out in a small struts
4. osteoblast beome trapped and mature into osteocytes
5. blood vessels enter and become trapped in developing bone 

Types of Fractures

1. closed or simple
2. open or compound
3.  tranverse
4. spiral
5. displaced
6. epphyseal
7. pott
8. colles

Marfan Syndome

• excessive cartilage formation at epiphyseal cartilage
• causes long slender limbs
• other connective tissue abnormalities cause cardiovascular issues 

Achondroplasia

• epiphyseal cartilage grows unusually slowly
• the limbs are short
• trunk is normal size 

Pituitary Growth Failure

• reduction in growth hormone leads to reduce epiphyseal cartilage activity and short bones
• rare due to treatment with synthetic growth hormone 

Appositional Bone Growth

• increases bone diameter of existing bones
• does not from original bones 

Endosteum

• incomplete cellular layer lining medullary cavity
• covers spongy bone and lines central canals
• it consists of simple layer of the osteoprogenitor cells
• if its incomplete the osteoclasts and osteoblasts remodel the matrix 

Periosteum Features

• smaller blood vessels
• lymphatic vessels
• sensory nerves 

Vascular Features

• Nutrient artery or vein
• nutrient foramen
• supplies osteons of compact bone with blood
• Metaphyseal artery or vein
• carry blood to/from metaphysis
• connects to epiphyseal arteries/veins 

Pelvis Surface Features

• crest
• fossa
• line
• spine
• ramus 

Four Bone Cell Types

1. Osteocytes
2.  Osteoblasts
3. Osteoprogenitor
4. Osteoclasts