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Lecture 5

PNB 2264 Lecture Notes - Lecture 5: Medullary Cavity, Connective Tissue, Hematoma

Physiology and Neurobiology
Course Code
PNB 2264

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Osteogenesis (new bone growth)
- This process works in one of two ways
- Intramembranous ossification (only the skull bones)
o Mesenchymal cells are directly converted to osteoblasts
o Osteoblasts then form new bone by laying down collagen and covering it with
calcium salts
Some osteoblasts make the periosteum
o Only happens in utero and in the skull
- Endochondral ossification
o Mesenchymal cells are first differentiated into chondroplasts
o Chondroblasts then produce a cartilage template
o Chondroblasts then differentiate into osteoblasts
o Happens in all bones outside skull
o Starts with cartilage template and cartilage grows longer and old cartilage turns
to bone
- Epiphyseal plate
o New cartilage replacement by appositional bone
o Similar to endochondral ossification
- Bones are made by one of two processes
o Require right cells and signals
Bone histology
- Composite material
o Like fiberglass boat
- Collagen (35%) and hydroxyapatite crystal (65%)
- Osteoblasts produce type 1 collagen (10% of mas) in layers
Bone Type
- Both IO and EO produce the same types of bones
o Compact or lamellar
- Why are there different bone types
o Because they are asked to do very different things
- Spongy bones on the inside, spongy on the inside
- Woven and lamellar bone
- Random vs organized
- Lamellar
o Looks like tree, rings, osteons
o Compact, dense and very strong
o Osteons are the clumps of rings
Bone anatomy
- Long bones longer than wide
o Humorous, femur, tibia, fibula etc
- Short bones same length and width
o Wrist bones, ankle bones
- Flat bones flat and curved
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