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MM3 Leesy > B6.068 - Bone Development Prework > Flashcards

B6.068 - Bone Development Prework Flashcards

1
Q

what is bone

A

tissue and organ

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2
Q

describe bone as a tissue

A

mineralized connective tissue
comprised of osteoblasts, osteocytes, osteoclasts
continuously remodeled

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3
Q

what orchestarates continuous remodeling of bone

A

balancing resorption by osteocytes and osteoclasts & formation of osteoblasts

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4
Q

what orchestrates bone modeling

A

osteocytes in response to mechanosensors

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5
Q

what helps with local control of bone

A

growth factors, cytokines

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6
Q

what helps with systemic hormonal control of bone

A

calcitonin, estrogen

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7
Q

describe endocrine regulation by bone

A

produces osteocalcin (hormone that has a role in bone mineralization, calcium ion homeostasis, insulin metabolism)

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8
Q

what does the skeletal system develop from

A
  1. paraxial mesoderm
  2. lateral plate mesoderm
  3. cranial neural crest cells
  4. mesenchyme of dermis
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9
Q

paraxial mesoderm forms what

A

somitomeres cranially, somites from occipital to sacral region

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10
Q

what happens in the 4th week of development to the somite

A

the ventral portion (sclerotome) becomes mesenchymal and some cells migrate and differentiate into fibroblasts, chondroblasts or osteoblasts

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11
Q

what contributes to the formation of the cranial vault

A

somitomeres and occipital somites

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12
Q

what happens to the caudal sclerotome

A

it gives rise to the vertebral column and ribs

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13
Q

what forms the bones of the pelvic and shoulder girdles, long bones of limbs and sternum

A

bone forming cells in the parietal/somatic layer of LPM

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14
Q

what contributes to the bones fo face and skull

A

neural crest cells

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15
Q

what happens in the flat bones of the skull

A

mesenchyme in the dermis differentiates directly into bone

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16
Q

where do osteoblasts come from

A

differentiate from mesenchymal stem cells in periosteum or are delivered by blood vessels

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17
Q

what do osteoblasts do

A 
secrete matrix (collagen 1 rich osteoid); catalyze mineralization (calcification ) of bosteoid via secretion o falk phosphatase to make bone
they then become trapped in the matrix they secrete
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18
Q

what are osteocytes

A

mature bone cells, have dendritic processes; formed when osteoblasts become trapped; maintain bone; role in mineral homeostasis via secretion of FGF23; sense mechanical load; viable for decades

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19
Q

what are osteoclasts

A

dissolve/absorb bone during growth by secreting H+ and collegenases. Differentiate from a fusion of monocyte/macrophage lineage precursors to form large multinucleated bone cells

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20
Q

what is RANK

A

a receptor for RANKL a pathway that regulates osteoclasts differentiation and activation. bone remodeling/repair
RANK - receptor activator for nuclear factor kapp abeta

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21
Q

describe RANK signaling

A

TNF receptor family member

present on osteoclasts and blasts

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22
Q

describe RANKL

A

expressed by osteoblasts

activates RANK and TF NFkB role of osteoclasts formation, differentiation and survival

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23
Q

what are chondroblasts

A

mesenchymal progenitor cells which will form chondrocytes in growing cartilage matrix

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24
Q

what are chondrocytes

A

produce and maintain the cartilagenous matrix (articular cartilage or cartilage model for bone formation)

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25
chondroclasts
involved in resorption of calcified cartilage; multinucleated giant cells
26
mesenchymal cells
multipotent; can differentiate in to osteoblasts, chondrocytes, other
27
what are neural crest cells
contribute to craniofacial cartilage and bone formation arise from border of non neural and neural ectoderm neural ectoderm rolls up to form neural tube
28
what happens in dorsal portion of neural tube
epithelial cells in dorsal poriton of neural tube undergo epithelial to mesenchymal transformation
29
compact bone
cortical, hard, dense, found near surface where strength is required
30
spongy bone
cancellous, mesh like, found in ends of long bones and center of flat bones
31
bone marrow
loose connective tissue that fills cavities of bone; produces red and white blood cells
32
periosteum
CT on surface of bone | outer fibrous layer has nerves and blood vessels; inner layer contains osteogenic cells
33
endosteum
inner lining of bones. Lines bone marrow cavity
34
haversian canal
duct in bone that contains blood vessels
35
osteon/haversian system
functional unit of compact bone
36
canalicular system
tiny canals extending from one lacuna to another connect ostocytes
37
elongation of bone
involves epiphyseal cartilages at ends of long bone but is it is the diaphysis that increases in length
38
where are sensory neurons in bone found
haversian canal and periosteum
39
what are the 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
what are the 2 types of initial bone formation
1. intamembranous ossification | 2. endochondral ossification
41
what is intramembranous ossification
mesenchyme differentiates directly into osteoblasts, which form bone (flat bones of skull)
42
what is endochondral ossification
mesenchymal cells give rise to chondroblasts, which differentiate into chondrocytes which make mineralized cartilage models (as an intermediate)
43
what are cartilage models
replaced by bone later in development
44
describe the process of intramembranous ossification
1. mesenchymal cells group into clusters and form multiple cell types; osteoblatss form ossification centers 2. secreted osteoid (unmineralized bone matrix) becomes calcified and traps oteoblasts which become osteocytes 3. trabecular matrix forms from osteoid and periosteum forms from surface osteoblasts 4. compact bone develops superficial to trabecular bone, and crowded blood vessels condense into red marrow
45
timeline of intramembranous ossification
begins in utero and continues in to adolescence | the last bones to ossify are the flat bones of the face, at the end of adolescence
46
benefits of intramembranous ossification
since the skull sutures and clavicles are not fully ossified at birth, the skull and shoulders deform during passage through the birth canal. The skull can also increase in size after birth for brain growth
47
bone formation from cartilage models
bones in extremities formed initially by endochondral ossification involves primary and secondary ossification centers
48
primary ossification centers
in long bones by week 12; responsible for prenatal bone growth in length
49
secondary ossification centers
in ends of bone
50
how does ossification of bone progress
from center of shaft (primary oss) to ends of bone (secondary oss)
51
what are the 3 dynamic regions of a long bone
epiphysis metaphysis diaphysiss
52
what is the metaphysis
site of secondary ossification centers; 3 subportions: 1. epiphyseal plate 2. bony portion 3. fibrous component
53
diaphyiss
mid portion/portion of bone that contains the medullary cavity; lengthens due to action of growth plates in metaphyses; is portion of bone that contains primary ossification center
54
describe the primary ossification center
endochondral ossification mesenchymal cells differentiate into chondroblasts, then chondrocytes cartilage model of future bony skeleton and perichondrium form. Capillaries penetrate cartilage; bringing osteoblasts. Perichondrium transforms into periostum and periosteal collar develops around mineralized cartilage. Primary ossification center develops
55
describe growth plates at birth
diaphysis is ossified 2 ends are still cartilaginous vessels invade epiphyses secondary ossification continues in epiphyses when bone at full length epiphyseal plates dissapear (age 13-15 F, 15-17 M)
56
where is bone age derived from
ossification centers in hands and wrists
57
cartilage matrix formation
following proliferation, chondrocytes secrete mostly collagen type 2 and sulfated proteoglycans forming cartilage model. Then chondrocytes move away from ends of bone and start to hypertrophy and secrete alkaline phosphatase. collagen reorganized into hexagonal lattices due to production of collagen type X ECM becomes mineralized/calcified by calcium phosphate chondrocytes eventually undergo apoptosis
58
describe vascularization of bone
chondrocytes undergo apoptosis as matrix mineralizes and nutrients can no longer reach the chondrocytes (cartilage is avascular!) before they die chondrocytes secrete matrix metalloproteinases to degrade ECM, blood vessels invade remaining space. This brings osteoblasts/clasts which can secrete osteoid
59
describe what the epiphyseal plate does
composed of 5 zones of cells and activity. cartilage formed towards epiphyseal side of plate. Cartilage is ossified towards diaphyseal side to lengthen bone
60
reserve/resting zone
chondrocytes anchor plate to osseous tissue of epiphysis
61
proliferation zone
chondrocytes proliferate
62
hypertrophic cartilage zone
chondrocytes increase in size, accumulate alkaline phosphatase
63
zone of calcification of cartilage
chondrocytes apoptose; cartilaginous matrix begins to calcify
64
zone of ossification
osteoclasts and blasts from diaphyseal side break down the calcified cartilage and replace with mineralized bone (primarily type 1 collagen)
65
appositional growth
bone diameter increases, occurs in all bones
66
when does appositional growth happen
when longitudinal growth stops
67
how does appositional growth happen
osteoclats resorb old bone that lines the medullary cavity meanwhile osteoblasts delivered via blood vessels produce new bone tissue beneath periosteum (intramembranous ossification) subperiosteal cortical bone forms and an increase in bone diameter results
68
appendicular skeleton components
4 bones in shoulder girdle, all the limbs and pelvis
69
achondroplasia
most common form of skeletal dysplasia AD related to FGF receptor 3 mutation primarily affects endochondral ossification in long bones and formation of base of skull
70
symptoms of achondroplasia
short limbs and fingers large skull small mid face prominent forehead
71
marfan syndrome
form of skeletal dysplasia related to fibrillin 1 gene mutation
72
symptoms of marfan syndrome
``` long limbs long face skeletal defects dilation an dissection of ascending aorta lens dislocation ```
73
congenital hyperpituitarism
production of excess growth hormone growth of soft tissues (enlargement of face) an bones of hands and feet: acromegaly gigantism
74
hypopituitarism
``` growth hormone affected; short stature normal arm and leg length fat around waist and face delated teeth development sluggish hair growth ```
75
congenital rickets
caused by severe vitamin D deficiency rarely in utero results in defective mineralization of cartilagenous growth plates
76
osteogenesis imperfecta
brittle bone disease hypomineralization of long bones of limbs leading to improper bones forming 90% linked to defects in COL1A1 or COL1A2 leading to reduced type 1 collagen production and altered bone matrix
77
symptoms of OI
frequent and multiple fracturesl bowing of long bones and or curvature of spine can result in short stature additional AEs on skin, muscle, joints, teeth, hearing, blue sclera may be observed

MM3 Leesy (12 decks)

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