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ANAT 261 > Bone Formation > Flashcards

Bone Formation Flashcards

1
Q

intramembranous ossification is typical where

A

flat bones

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2
Q

name flat bones - 4

A

part of mandible
maxilla
occipital
temporal and parietal vones

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3
Q

what does metaphysis mean

A

head, spongy

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4
Q

what is periosteum

A

dense ct sheath with osteoprogenitor cells

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5
Q

what is diaphysis

A

middle

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6
Q

what is epiphyseal line

A

remnant of epiphyseal plate

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7
Q

where does intramembranous ossification take place

A

within plates of mesenchymal cells
(derived from mesoderm layer)

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8
Q

describe intramembranous ossification - 1

A

group of mesenchymal cells differentiate (need signal) into osteoblasts (primary ossification center)
synthesis of extracellular matrix
encapsulation of osteocytes
formation of spicules

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9
Q

what is a bone spicule

A

piece
made by osteoblasts
or
chewed up by osteoclast

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10
Q

describe intramembranous ossification - 2

A

several similar secondary ossification centers develop on the periphery
the mesenchymal cells differentiate into periosteum
Ossification centers grow radially and fuse
resulting bone is spongy

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11
Q

describe intramembranous ossification - 3

A

same concept as primary ossification centers
ossification grows out of sites
makes one sheet of bone by fusing together (like soft spot on baby head)
forms periosteum - eventually fuses to flat bone

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12
Q

describe perichondrium vs periosteum

A

perichondrium = around cartilage
periosteum = around bone BUt has osteoprogenitor cells
both dense ct

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13
Q

where does endochondral ossification take place

A

within a piece of hyaline cartilage with a similar shape of bone to be formed
all long bones in body come from piece of hyaline cartilage

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14
Q

what is cartilage surrounded by (endochondral ossification)

A

perichondrium
Except in future articular surfaces

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15
Q

describe primary ossification center of endochondral ossification - 1

A

at level of diaphysis
perichondrium is transformed into periosteum which deposits bone = bone collar

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16
Q

describe primary ossification center of endochondral ossification - 2

A

bone collar prevents diffusion of nutrients
cartilage degenerates (hypertrophy and cell death followed by calcification of ECM)

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17
Q

describe primary ossification center of endochondral ossification - 3

A

blood vessels invade from perichondrium/periosteum
invade spaces left by the degenerating chondrocytes
pushes through bone collar lengthwise through cartilage and drags periosteum with it - and osteoprogenitor cells which create osteoblasts

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18
Q

describe primary ossification center of endochondral ossification - 4

A

differentiating osteoblasts divide and secrete ecm
ecm made lengthwise - makes space for future bone marrow canal
chewed up cartilage and lots of bone marrow spicles

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19
Q

describe secondary ossification center of endochondral ossification - 1

A

take places at epiphysis of the future bone (head)

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20
Q

describe secondary ossification center of endochondral ossification - 2

A

cartilage degenerates
invaded by blood vessels from perichondrium (transformed into periosteum)

21
Q

describe secondary ossification center of endochondral ossification - 3

A

cartilage persists in articular surface and epiphyseal plate
mainly where primary meets secondary
articular surfaces = top and bottom, parts that go into joints

22
Q

describe bone remodelling

A

osteoclasts are active in resorption of calcified cartilage and woven bone leading to formation of a hollow marrow

23
Q

name layers of epiphyseal plate - top to bottom - 5

A

zone of resting cartilage
zone of proliferation
zone of hypertrophy
zone of cell death
zone of mixed spicules

24
Q

describe zone of resting cartilage (epiphyseal plate)

A

chondrocytes

25
Q

describe zone of proliferation (epiphyseal plate)

A

flat cells
actively dividing (chondrocytes)
looks like stack of coins

26
Q

describe zone of hypertrophy (epiphyseal plate)

A

cells swell with fluid
lacunae swell and then burst = cell death

27
Q

describe zone of cell death (epiphyseal plate)

A

dying cells
many osteoclasts, some osteoblasts
calcified cartilage - being chewed up, light coloured area, no cells

28
Q

describe zone of mixed spicules (epiphyseal plate)

A

zone of mixed bone

29
Q

describe how endochondral ossification permits growth in length

A

growth in length of long bone occurs by proliferation of chondrocytes in epiphyseal plate
rate of chondrocyte proliferation and bone formation = destruction of spicules
the thickness of epiphyseal plate does not change but it is displaced away from middle of diaphysis
results in net growth of length of bone

30
Q

what are spicules not formed by

A

not formed by lamellar bone – this type of bone is called spongy bone

31
Q

does thickness of epiphyseal plate change

A

NOOOO
it just gets displaced as zone of cell death and zone of mixed spicules are turned over
Epiphyseal plates move further away from each other = how bone grows in length

32
Q

what is bone growth associated with

A

partial remodeling - shaping

33
Q

describe bone growth - 1

A

growth in length - chondrogenesis
epiphyseal plate works to increase length of long bone until 20 years old

34
Q

describe bone growth - 2

A

radial growth - perichondrium
osteoprogenitor cells
overtime, bone on outside = length in head of bone

35
Q

describe bone growth - 3

A

formation of new spicules by lateral invasion of blood vessels
primary ossification center - osteoclasts chew up

36
Q

describe bone growth - 4

A

remodeling of the funnel - periosteal osteoclasts
osteoclasts chew up and work to remodel funnel

37
Q

describe bone growth - 5

A

addition of bone from osteoblasts on periosteal surface

38
Q

describe bone repair

A

periosteum is needed in case of breakig a bone
periosteal proliferation –> hyaline cartilage –> newly formed primary and secondary bone –> healed fracture (secondary bone)
periosteum kicks in and makes new hyaline cartilage, but not very sturdy, so doc sets it, new cartilage comes from fibers
then follows same process of endochondral ossification = cartilage –> bone (left with compact bone)

39
Q

why can bones telescope

A

hyaline cartilage not strong enougb

40
Q

describe concentration of calcium in blood

A

calcemia
Concentrations in tissue and blood must be kept constant

41
Q

what happens if nutritionally deficient in calcium

A

decalcification of bones

42
Q

what can calcium be mobilized by

A

influence of parathyroid hormone = PTH

43
Q

describe PTH

A

activates osteoclasts
acts primarily on osteoblasts –> which stop producing bone and starts secretion of osteoclast stimulating factor (since want to conserve calcium)

44
Q

describe calcitonin

A

Hormone
produced by thyroid gland
inhibits bone resorption (osteoclasts)

45
Q

describe pituitary dwarfism

A

lack of GH (growth hormone)
2 types of dwarfism
epiphyseal plate does not grow
or mutation (reception issue) and also does not grow (does not work)

46
Q

describe gigantism

A

excess GH in youngsters
epiphyseal plate does not stop growing at 20
usually caused by a tumour in thyroid gland

47
Q

describe acromegaly

A

excess GH in adults - periosteal growth
if over 20 = epiphyseal plate stops growing but since excess growth hormone so long bones cannot grow anymore but causes long hands and feet

48
Q

growth occurs up to what age

A

20 years old in humans
regulated by growth hormone - GH

ANAT 261 (27 decks)

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