histology 4- ossification Flashcards
what are the two types of osteogenesis
- intramembranous ossification
2. endochondral ossification
intramembranous ossification
- no hyalin cartilage model precursor
- mesenchyme –> bone (directly!)
- flat bones mostly
- begins week 8 of gestation in humans
endochondral ossification
- hyalin cartilage model precursor
- mesenchyme–> hyalin cartilage –> bone
- most short and long bones
- present in all long bone by week 12
primary ostificatoin center
diaphysis
secondary ostification center
epiphysis
bone increases in length with what kind of growth
intersitial
bone growth length, 5 zones
- zone of resting cartilage
- zone of proliferating cartilage
- zone of hypertrophic cartilage
- zone of calcified cartilage
- zone of ossification
zone of resting cartilage
closest to the epiphysis.
nothing is going on here.
chondrocytes sit in lacunae bythemselves
zone of proliferating cartilage
chondrocyes undergoing mitosis.
as they do this they are forming isogenous groups. divide so they stack up like COINS. this division process pusshes the diaphysis away from the epiphysis, causes lengthening of the long bone. (also are producing matrix)
zone of hypertrophic cartilage
chondrocytes sitting in lacunae start increasing in size (hypertrophy)
causes matrix to shrink and calcify.
when this happens chondocytes die. spaces open up
what prevents hyalin cartilage from getting too big
osteoclast chase
chrondocytes run
bone increases in width with what kind of growth
appositional growth
bone width grown at two places
periosteal layer- osteoblast secret bone matrix
endosteal layer- osteoclast break down bone matrix
two controls impacting bone remodeling
- negative feedback loop- calcium homeostasis
2. bones response to mechanical stress and gravity
negative feeback loop, calcium homeostatsis hormones
calcitonin
parathyroid
