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ANAT 261 Lecture Notes - Type I Collagen

Anatomy & Cell Biology
Course Code
ANAT 261
Jason Young

of 2
Lab 4 – Bone
Two types of bone:
1. Trabecular (or spongy or cancellous) bone
a. Woven (immature, disorganized fibres)
b. WHERE: ends of long bones, craniofacial bones, immature
bone, thin bones
2. Compact bone
a. Lamellar (mature, organized fibres)
b. WHERE: shafts of long bones
Components and Structure
- bone is specialized connective tissue
- extracellular matrix is predominantly collagen type I
- Cells found in bone:
oosteoblasts secrete bone matrix
basophilic, cuboidal cells with eccentric (not centred)
found in the periosteum and line the Haversian
oosteocytes structural cells of bone
osteoblasts that get trapped in ECM
flattened, with flatten nuclei
oosteoclasts large multinucleated cells
resorb bone; regulate blood [Ca]
-periosteum CT sheath that surrounds bone
omade of two layers:
fibrous layer outer layer; dense irregular CT
(fibrocytes); collagen type I
osteogenic layer inner layer; osteoblasts
oa single layer of osteoblasts and osteoprogenitor cells that
line the marrow cavity
-inner circumferential system
omade by the osteoblasts of the endosteum
oright before endosteum
-outer circumferential system
omade by the osteoblasts of the periosteum
ojust below periosteum
-Haversian systems (also called osteons)
ocircular rings, surrounded by cementing lines
(differentiates between systems)
oscattered between OCS and ICS
ocontain a Haverisan canal that runs parallel to bone’s axis
and bring nerves and blood vessels to the bone
Lab 4 – Bone
oVolksmann canals run perpendicularly to and connect
Haversian canals (will be seen in cross section)
oimmature bones have large Haversian canals
-interstitial systems
obone surrounding the Haversian systems
onot concentric, but rather parallel
- SUMMARY [from outside to inside]
oHaversian systems and interstitial systems
omarrow cavity
Epiphyseal Plate
- allows long bones to grow in length
- at the junction of epiphysis (end) and diaphysis (shaft)
osecondary ossification center of endochondral ossification
- from outside to inside:
ozone of resting cartilage
hyaline cartilage with chondrocytes and isogenic
ozone of proliferation
rapidly dividing chondrocytes (interstitial growth)
cells look like a stack of coins
ozone of hypertrophy
cells begin to swell
cartilage ECM begins to calcify (ECM appears to fade)
ozone of cell death
nuclei irregular
empty lacuna
ozone of mixed spicules
mixture of calcified cartilage and bone
osteoblasts, osteocytes, and osteoclasts can all be
Osteoclast Regulation
oacts to tone” down Ca in the blood (no increase in Ca)
oinhibits bone resorption by inhibiting osteoclasts
oproduced by the thyroid gland
-parathyroid hormone (PTH)
oincreases Ca in blood by activating osteoclasts
otherefore increases bone resorption