Bone Formation

Question 1

intramembranous ossification is typical where

Answer 1

flat bones

Question 2

name flat bones - 4

Answer 2

part of mandible
maxilla
occipital
temporal and parietal vones

Question 3

what does metaphysis mean

Answer 3

head, spongy

Question 4

what is periosteum

Answer 4

dense ct sheath with osteoprogenitor cells

Question 5

what is diaphysis

Answer 5

middle

Question 6

what is epiphyseal line

Answer 6

remnant of epiphyseal plate

Question 7

where does intramembranous ossification take place

Answer 7

within plates of mesenchymal cells
(derived from mesoderm layer)

Question 8

describe intramembranous ossification - 1

Answer 8

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

Question 9

what is a bone spicule

Answer 9

piece
made by osteoblasts
or
chewed up by osteoclast

Question 10

describe intramembranous ossification - 2

Answer 10

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

Question 11

describe intramembranous ossification - 3

Answer 11

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

Question 12

describe perichondrium vs periosteum

Answer 12

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

Question 13

where does endochondral ossification take place

Answer 13

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

Question 14

what is cartilage surrounded by (endochondral ossification)

Answer 14

perichondrium
Except in future articular surfaces

Question 15

describe primary ossification center of endochondral ossification - 1

Answer 15

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

Question 16

describe primary ossification center of endochondral ossification - 2

Answer 16

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

Question 17

describe primary ossification center of endochondral ossification - 3

Answer 17

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

Question 18

describe primary ossification center of endochondral ossification - 4

Answer 18

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

Question 19

describe secondary ossification center of endochondral ossification - 1

Answer 19

take places at epiphysis of the future bone (head)

Question 20

describe secondary ossification center of endochondral ossification - 2

Answer 20

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

Question 21

describe secondary ossification center of endochondral ossification - 3

Answer 21

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

Question 22

describe bone remodelling

Answer 22

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

Question 23

name layers of epiphyseal plate - top to bottom - 5

Answer 23

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

Question 24

describe zone of resting cartilage (epiphyseal plate)

Answer 24

chondrocytes

Question 25

describe zone of proliferation (epiphyseal plate)

Answer 25

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

Question 26

describe zone of hypertrophy (epiphyseal plate)

Answer 26

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

Question 27

describe zone of cell death (epiphyseal plate)

Answer 27

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

Question 28

describe zone of mixed spicules (epiphyseal plate)

Answer 28

zone of mixed bone

Question 29

describe how endochondral ossification permits growth in length

Answer 29

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

Question 30

what are spicules not formed by

Answer 30

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

Question 31

does thickness of epiphyseal plate change

Answer 31

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

Question 32

what is bone growth associated with

Answer 32

partial remodeling - shaping

Question 33

describe bone growth - 1

Answer 33

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

Question 34

describe bone growth - 2

Answer 34

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

Question 35

describe bone growth - 3

Answer 35

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

Question 36

describe bone growth - 4

Answer 36

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

Question 37

describe bone growth - 5

Answer 37

addition of bone from osteoblasts on periosteal surface

Question 38

describe bone repair

Answer 38

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)

Question 39

why can bones telescope

Answer 39

hyaline cartilage not strong enougb

Question 40

describe concentration of calcium in blood

Answer 40

calcemia Concentrations in tissue and blood must be kept constant

Question 41

what happens if nutritionally deficient in calcium

Answer 41

decalcification of bones

Question 42

what can calcium be mobilized by

Answer 42

influence of parathyroid hormone = PTH

Question 43

describe PTH

Answer 43

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

Question 44

describe calcitonin

Answer 44

Hormone produced by thyroid gland inhibits bone resorption (osteoclasts)

Question 45

describe pituitary dwarfism

Answer 45

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)

Question 46

describe gigantism

Answer 46

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

Question 47

describe acromegaly

Answer 47

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

Question 48

growth occurs up to what age

Answer 48

20 years old in humans regulated by growth hormone - GH