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MM Test 3 > B6.068 Prework 1: Bone Development Overview / Appendicular Skeleton > Flashcards

B6.068 Prework 1: Bone Development Overview / Appendicular Skeleton Flashcards

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1
Q

why is bone a tissue?

A

mineralized connective tissue
comprised of different cell types that communicate with one another
continuously remodeled
processes under local and systemic hormonal control

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2
Q

how is bone modeling orchestrated

A

by osteocytes in response to mechanosensors

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3
Q

local control of bone modeling

A

growth factors

cytokines

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4
Q

systemic hormonal control of bone modeling

A

calcitonin

estrogen

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5
Q

why is bone an organ

A

collectively comprises the skeletal system

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6
Q

functions of the skeletal system

A

locomotion
structural support
protection for internal organs
mineral reservoir for calcium and phosphate (Ca homeostasis)
contains bone marrow which produces red and white blood cells
endocrine regulation

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7
Q

endocrine function of bone

A

produces osteocalcin

hormone that has a role in bone mineralization, calcium ion homeostasis, and insulin metabolism

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8
Q

embryologic components of the skeletal system

A

a) paraxial mesoderm
b) lateral plate mesoderm (parietal)
c) cranial neural crest cells
d) mesenchyme of dermis

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9
Q

how does the paraxial mesoderm contribute to the skeletal system

A

forms somitomeres cranially and somites from the occipital to sacral region

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10
Q

ventral portion of the somite

A

sclerotome

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11
Q

sclerotome contribution to skeleton

A

becomes mesenchymal at the end of the 4th week
comprised of loosely organized connective tissues
mesenchymal cells can migrate and differentiate to form multiple cell types (fibroblasts, chondroblasts, osteoblasts)
caudal portion gives rise to vertebral column and ribs

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12
Q

cranial vault and base of skull origin

A

paraxial mesoderm:
somitomeres
occipital somites

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13
Q

parietal lateral plate mesoderm contribution to skeletal system

A

bones of pelvic and shoulder girdles
long bones of limbs
sternum

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14
Q

neural crest cell contribution to skeletal system

A

bones of face and skull

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15
Q

mesenchyme of dermis contribution to skeletal system

A

flat bones of the skull

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16
Q

osteoblast origin

A

mesenchymal stem cells in periosteum

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17
Q

osteoblast function

A

secrete the matrix (collagen 1 rich osteoid)
catalyze mineralization (calcification) of osteoid via secretion of alk phos to make bone
become trapped in the matrix they secrete

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18
Q

osteocytes

A 
mature bone cells w dendritic processes
formed when osteoblasts become trapped
maintain bone
role in mineral homeostasis via FGF23
sense mechanical load
viable for decades
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19
Q

osteoclasts

A

dissolve/absorb bone during growth by secreting H+ and collagenases

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20
Q

osteoclast origin

A

differentiate from a fusion of monocyte/ macrophage lineage precursors to form large multinucleate bone cells

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21
Q

RANK signaling pathway

A

regulates osteoclast differentiation and activation, and bone remodeling/repair

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22
Q

RANK

A

receptor activator for NFKB

  • TNF receptor family
  • present on pre-osteoclasts and osteoclasts
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23
Q

RANK-L

A

expressed by osteoblasts
activates RANK & transcription factor NFKB
role in osteoclast formation, differentiation and survival

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24
Q

chondroblasts

A

mesenchymal progenitor cells which will form chondrocytes in the growing cartilage matrix

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25
chondrocytes
produce and maintain the cartilaginous matrix | articular + hyaline model for bone formation
26
chondroclasts
involved in resorption of calcified cartilage | multinucleated (giant) cells
27
discuss the steps of neural crest cells forming craniofacial cartilage and bone
1. arise from border of non neural and neural ectoderm 2. neural ectoderm rolls up to form neural tube 3. epithelial cells in dorsal portion of the neural tube undergo epithelial to mesenchymal transformation 4. neural crest migrate out and away from neural tube 5. forms head and neck
28
compact bone
cortical | hard, dense, found near surface where strength is required
29
spongy bone
cancellous, trabecular | mesh like, found in ends of long bones and center of flat bones
30
bone marrow
loose CT that fills cavities of bone | produces red and white blood cells
31
periosteum
CT on the surface of bone outer fibrous layer = nerves and BVs inner layer = osteogenic cells
32
endosteum
inner lining of bones | lines bone marrow cavity
33
Haversian canal
duct in bone w blood vessels
34
Osteon / Haversian system
functional unit of compact bone
35
canalicular system of bones
tiny canals extending from one lacuna to another | connect osteocytes
36
vascularity of bones
bone cells must be in close proximity to capillaries | vessels present in bone marrow, Haversian canals, and periosteum
37
elongation of bones
involves epiphysial cartilages at the ends of the long bone, but it is the diaphysis that increases in length
38
newly formed bone vs matured bone
new: appears woven w haphazard strands of collagen | eventually transforms to be lamellar (parallel arrays of mineralized osteoid)
39
4 phases of skeletal development
1. migration of pre-skeletal mesenchymal cells to sites of future skeletogenesis 2. interaction of mesenchymal cells with epithelial cells 3. interaction leads to mesenchymal condensation 4. followed by differentiation to chondroblasts or osteoblasts
40
2 types of bone formation
intramembranous ossification | endochondral ossification
41
intramembranous ossification
mesenchyme differentiated directly into osteoblasts, which form bone e.g. flat bones of skull
42
endochondral ossification
mesenchymal cells give rise to chondroblasts, which differentiate to chondrocytes which make mineralized cartilage models cartilage models replaced by bone e.g. base of skull, limb long bones, end of irregular bones (ribs and vertebrae)
43
steps of intramembranous ossification
1. mesenchymal cells group into clusters and form multiple cell types; osteoblasts form ossification centers 2. secreted osteoid becomes calcified and traps osteoblasts which become osteocytes 3. trabecular matrix forms from osteoid and periosteum forms from surface osteoblasts 4. compact bone develops superficial to the trabecular bone, and crowded blood vessels condense into red marrow
44
time line of intramembranous ossification
begins in utero | continues into adolescence
45
last bones to ossify
flat bones of face (at end of adolescence)
46
benefits of later intramembranous ossification
skull sutures and clavicles are not fully ossified at birth, skull and shoulders deform during passage through the birth canal skull can increase in size to allow for postnatal bone growth
47
primary ossification centers
part of endochondral ossification present in long bones by week 12 of development responsible for prenatal bone growth
48
secondary ossification centers
ends of bone | where growth progresses after birth
49
epiphysis
articular portion of long bones
50
metaphysis
``` site of secondary ossification 3 subportions: -epiphysial plate (cartilaginous) -bony portion -fibrous component (periphery of growth plate) ```
51
diaphysis
midportion (shaft) portion of bone that contains the medullary cavity lengthens due to action of growth plates in metaphyses contains primary ossification center
52
how does the primary ossification center form
1. mesenchymal cells differentiate into chondroblasts, then chondrocytes 2. cartilage model of the future bony skeleton and perichondrium form 3. capillaries penetrate cartilage, bringing osteoblasts / perichondrium transforms to periosteum / periosteal collar develops around mineralized cartilage / primary ossification center develops (in diaphysis) 4. cartilage and chondrocytes continue to grow at ends of the bone
53
development of secondary ossification centers
at birth: the diaphysis is ossified and 2 ends of bone are still cartilaginous vessels invade epiphyses secondary ossification continues in epiphyses
54
when do epiphysial plates disappear
approx. age 13-15 in females, 15-17 in males
55
bone age information
derived from ossification centers in hands and wrists
56
how is a cartilage model formed
chondrocytes secrete collagen type 2 and sulfated proteoglycans
57
what happens after a cartilage model is formed
chondrocytes move away from ends of bone, begin to hypertrophy & secrete alk phos collagen is reorganized into hexagonal lattices due to production of collagen type X ECM becomes calcified by calcium phosphate chondrocytes eventually undergo apoptosis
58
why do chondrocytes undergo apoptosis?
matrix mineralizes and nutrients can no longer reach them because cartilage is avascular
59
what happens when chondrocytes die?
secrete matrix metalloproteinases to degrade ECM | blood vessels invade resulting spaces, enlarging the cavities and bringing osteoblasts and chondroblasts
60
what are the 5 zones of the epiphyseal plate
``` EPIPHYSIS reserve/ resting zones proliferation zone hypertrophic cartilage zone zone of calcification of cartilage zone of ossification ```
61
reserve/resting zone
chondrocytes anchor plate to osseous tissue of epiphysis
62
proliferation zone
chondrocytes proliferation
63
hypertrophic cartilage zone
chondrocytes increase in size, accumulate alk phos
64
zone of calcification of cartilage
chondrocytes apoptose; cartilaginous matrix begins to calcify
65
zone of ossification
osteoclasts and osteoblasts from the diaphyseal side break down the calcified cartilage and replace with mineralized bone (type 1 collagen)
66
what types of bones undergo appositional growth
occurs in all bones! when bones increase in length, they also increase in diameter diameter growth continues after longitudinal growth ceases
67
cells involved in appositional growth
osteoclasts resorb old bone that lines the medullary cavity osteoblasts produce new bone tissue beneath periosteum subperiosteal cortical bone forms and an increase in bone diameter results
68
how many bones in the shoulder girdle
4 | clavicle and scapula each side
69
how many bones in the arm and forearm
6 | humerus, ulna, radius
70
how many bones in the hand
``` 58 16 carpals 10 metacarpals 28 phalanges 4 sesamoid ```
71
how many leg bones
8 | femur, tibia, patella, fibula
72
epidemiology of achondroplasia
most common form of skeletal dysplasia | 1/20,000 live births
73
genetics of achondroplasia
autosomal dominant | related to FGF Receptor 3 mutations
74
systems impacted by achondroplasia
endochondral ossification in long bones and formation of base of skull
75
effects of achondroplasia
short limbs and fingers large skull small midface prominent forehead
76
effects of Marfan Syndrome
``` long limbs long face sternal defects dilation and dissection of ascending aorta lens dislocation ```
77
genetics of Marfan
fibrillin 1 gene mutations
78
when do symptoms of Marfan appear?
symptoms may not appear / be diagnosed until late in childhood / early adulthood
79
what is congenital hyperpituitarism
production of excess growth hormone
80
acromegaly
growth of soft tissues (enlargement of face), ad bones of hands and feet
81
gigantism
excessive growth (height and body proportions)
82
what is hypopituitarism
growth hormone is affected
83
effects of hypopituitarism
short stature fat around waist and face delayed teeth development sluggish hair growth
84
congenital rickets
caused by severe maternal def in vit D rare results in defective mineralization of cartilaginous plates
85
what is osteogenesis imperfecta
reduced type 1 collagen production and altered bone matrix hypomineralization of the long bones of limbs improper bones form
86
bone effects of osteogenesis imperfecta
shortened, bowed, easily fractured bones frequent and multiple fractures bowing of bones and curvature of spine can result in short stature
87
genetics of osteogenesis imperfecta
90% linked to defects in COL1A1 or COL1A2
88
non-bone effects of osteogenesis imperfecta
skin, muscles, joints, teeth, hearing, blue sclera

MM Test 3 (31 decks)

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