Bone formation Flashcards
Lamellated bone
is in spongy bone trabeculae. Bone’s lamellae are more or less parallel to each other
Concentric lamellae (Haversian systems)
Characteristic of compact bone. highly organized
Intramembranous ossification
takes place in membrane of mesenchyme
Endochondral ossification
takes place in hyaline cartilage
Difference of collagen fibers in primary and secondary bone
Primary has randomly arranged collagen fibers. Secondary has parallel collagen fibers
What are osteoids laid down by
osteoblasts
Basics of bone formation
1) primary bone is first formed by osteoblasts, which lay down osteoid
2) Osteoclasts come in to break down the bone
3) secondary bone is made by osteoblasts
4) Osteoid becomes mineralized
How do we get blood to bone
Bone forms around blood vessels
Intramembranous Ossification
-Bone forms directly within a membrane of highly bascular mesnchyme.
Flat bones form this way
Steps of Intramembranous Ossification
1) mesenchymal cells
2) osteoprogenitor cells
3) Osteoblasts
4) osteoid
Endochondral ossification
bone forms in hyaline cartilage model
how long bones are formed
Hyaline cartilage model
1) miniature version of bone to be is made of hyaline cartilage
2) grow interstitially and appositionally
3) perichondrium becomes vascularized and cells differentiate into osteoprogenitor cells
4) Osteoprogenitor cells start synthesizing bone matrix and perichondrium converts into a periosteum
5) osteogenic bud grows. Osteoblasts come in and degrade inside of calcified cartilage matrix
6) primary and secondary center of ossification
Mnemonic for cartilage
C (calcification)
D (death)
E (erosion)
R (replaced
Secondary center of ossification
forms after birth
bone forms at epiphysis but no bone collar is formed.
Hyaline cartilage persists where
articular surfaces of bone
epiphyseal (growth) plates
How does hyaline cartilage grow at articular cartilage
interstitial growth only - no perichondrium, so you can’t have appositional growth
Zone of reserve cartilage
consists of hyaline cartilage
mitosis still takes place, but not much
Zone of proliferation
Lots of mitosis taking place here. Lays down matrix
Chondrocytes look like a stack of pennies
Zone of maturation
interstitial growth is occuring here
Zone of hypertrophy
looks swollen because they accumulate glycogen and vacuoles
No addition of new cells here
Release of alkaline phosphatase. Calcification of hyaline cartilage matrix occurs here
Zone of calcified cartilage
hyaline cartilage remnant
Zone of resportion and ossification
Osteoblasts lay down osteoid
Alkaline phosphatase
causes increase in phosphate conc, and even more of an increase in calcium ion conc
Matrix vesicles
membrane bubbles that are released into matrix. Stimulated by osteoblasts
Bone repair
Clean up debris with neutrophiles and macrophages
form new connective tissue
