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Flashcards in histology 4- ossification Deck (18)
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1

what are the two types of osteogenesis

1. intramembranous ossification
2. endochondral ossification

2

intramembranous ossification

- no hyalin cartilage model precursor
- mesenchyme --> bone (directly!)
- flat bones mostly
- begins week 8 of gestation in humans

3

endochondral ossification

- hyalin cartilage model precursor
- mesenchyme--> hyalin cartilage --> bone
- most short and long bones
- present in all long bone by week 12

4

primary ostificatoin center

diaphysis

5

secondary ostification center

epiphysis

6

bone increases in length with what kind of growth

intersitial

7

bone growth length, 5 zones

1. zone of resting cartilage
2. zone of proliferating cartilage
3. zone of hypertrophic cartilage
4. zone of calcified cartilage
5. zone of ossification

8

zone of resting cartilage

closest to the epiphysis.
nothing is going on here.
chondrocytes sit in lacunae bythemselves

9

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)

10

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

11

what prevents hyalin cartilage from getting too big

osteoclast chase
chrondocytes run

12

bone increases in width with what kind of growth

appositional growth

13

bone width grown at two places

periosteal layer- osteoblast secret bone matrix
endosteal layer- osteoclast break down bone matrix

14

two controls impacting bone remodeling

1. negative feedback loop- calcium homeostasis
2. bones response to mechanical stress and gravity

15

negative feeback loop, calcium homeostatsis hormones

calcitonin
parathyroid

16

what cells produce calcitonin

parafollicular cells

17

what does calcitonin do?

inhibit reabsorption
inhibit osteoclast
increase activity of osteoblast
Ca blood levels go down

18

increase blood calcium levels

parathyroid glands secrete parathyroid hormone.
causes osteoclast activity to increase