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Embryology Exam 2 > L14-15: Musculoskeletal Development > Flashcards

L14-15: Musculoskeletal Development Flashcards

(56 cards)

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1
Q

list the 4 major pathways for bone/cartilage differentiation

A
  1. common path
  2. membranous bone path
  3. permanent cartilage path
  4. endochondral bone path
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2
Q

the common pathway

A
  1. mesenchyme induced to enter
  2. N-cadherin production promotes their condensation
  3. TGF-b stim synthesis of fibronectin and N-CAM
  4. aggregated state of cells is stabilized
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3
Q

membranous bone pathway

A
  1. enter after common path
  2. TFs Runx-2 and Osx
  3. mesenchymal cells differentiate into osteoblasts
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4
Q

permanent cartilage pathway

A
  1. from common
  2. mesenchymal condensation forms chondroblasts
  3. Sox9 causes them to secrete collagen II and cartilage matrix
  4. sox9 is continually expressed in permanent cartilage
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5
Q

endochondral bone pathway

A
  1. from step 3 of permanent cartilage path
  2. Runx-2, ihh, BMP-6 induce cartilage to undergo hypertrophy
  3. these cells secrete bone proteins and vascular endothelial growth factor
  4. invading BVs erode the hypertrophic cartilage and bring in osteoblasts to replace cartilage w/ bone
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6
Q

centrum formation

A

derived from ventral and medial parts of paired sclerotomes

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7
Q

neural arches - formation

A

arise from dorsal regions of sclerotomes

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8
Q

costal processes and ribs - formation

A

prox development depends on expression of Myf-5 and Myf-6

distal development depends on BMP signals from somatopleural mesoderm

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9
Q

Hox gene boundaries in developing vertebral column (3)

A
  1. occipital-cervical boundary
    Hox3
  2. cervical-thoracic
    Hox6
  3. attached-floating
    Hox9
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10
Q

formation of a proatlas

A

result of Hoxa7 transgene

instead of the atlas having a hole for the dens of the axis to extend into

the centrum cells of the atlas stay with it instead of attaching to the axis

atlas and axis form as normal vertebra

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11
Q

development of the clavicle

A

arises from neural crest**unlike other bones

follows intramembranous pathway

one of first bones to ossify

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12
Q

the developing embryonic skull is composed of

A

neurocranium
viscerocranium
occipital sclerotomes

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13
Q

viscerocranium

A

surrounds oral cavity and pharynx

refers to pharyngeal arches

has a cartilaginous and membranous portion

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14
Q

cartilaginous portion of the viscerocranium

A

pharyngeal arch I
–meckel’s cartilage, malleus, incus

pharyngeal arch II
–reichert’s cartilage, stapes, styloid

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15
Q

membranous portion of the viscerocranium (10)

A 
forms:
part of temporal
zygomatic
maxillary
nasal
lacrimal
palatine
vomer
pterygoid plates
mandible
tympanic ring
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16
Q

________ portion of ________ is derived from parachordal cartilages and occipital _______ .

A

basioccipital portion of chondrocranium

occipital sclerotomes

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17
Q

elongation of primary ossification centers is due to ?

A

Shh

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18
Q

bones of neurocranium arise as a result of ? and are characterized by ?

A

inductive interactions of surrounding mesenchyme

transient appearance of collagen II and cartilage-specific proteoglycans

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19
Q

intersection of more than 2 bones forms a ?

A

fontanelle

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20
Q

explain the pathway resulting in fusion of sutures

A
  1. noggin is expressed in all sutures
    - –normally inhibits BMP so sutures don’t close before we’re done growing
  2. FGF-2 is expressed and inhibits noggin
  3. BMP is expressed in all sutures normally
  4. w/o noggin BMP causes closure of sutures
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21
Q

explain the pathway resulting in fusion of sutures

A
  1. noggin is expressed in all sutures
    - –normally inhibits BMP so sutures don’t close before we’re done growing
  2. FGF-2 is expressed and inhibits noggin
  3. BMP is expressed in all sutures normally
  4. w/o noggin BMP causes closure of sutures
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22
Q

unlike smooth muscle, skeletal muscle originates in ?

A

either somites or somitomeres

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23
Q

list the stages in differentiation of skeletal muscle

Study These Flashcards
A

myogenic cells
myoblasts
myotubes
muscle fibers

24
Q

myogenic cells are kept in labile state by ? (non-mitotic)

25
myogenic cells
originate in somites resemble mesenchymal cells mitotic cells restricted to muscle forming line
26
myoblasts
derived from myogenic cells w/ p21 activated post-mitotic
27
myotube formation
formed when myoblasts line up and adhere to one another requiring Ca-dependent CAMs
28
myotube characteristics
``` characterized by the appearance of: actin myosin troponin tropomyosin ``` forming myofibirls into sarcomeric arrangement nuclei move to periphery
29
satellite cells attach to ?
myotubes before basal lamina is laid down located between sarcolemma and basal lamina of myofiber
30
characteristics of satellite cells
mitotic and myogenic can fuse w/ muscle fiber and help w/ growth generally quiescent
31
satellite cells do not form ?
new muscle fibers
32
satellite cell function
``` function as stem cells to help w/ muscle fiber growth ```
33
satellite cells can become mitotic in times of stress, resulting from influence of what factors
HGF (hepatic growth factor) binds to receptor C-Met on satellite cell
34
satellite cells can give rise to _________ cells to do what ?
myogenic precursor cells to replace damaged muscle by proliferating, fusing and differentiating into skeletal muscle fibers
35
p21
is absolutely needed for myogenic cells to become committed myoblasts
36
p21
is absolutely needed for myogenic cells to become committed myoblasts
37
mitotic capability of myogenic cells
FGF and TGF-b maintain them in labile state
38
loss of mitotic capability for myogenic cells
due to p21 | produced by myogenic cells in response to myogenic regulatory factors
39
MyoD family function
able to convert non-muscle cells to cells capable of expressing muscle proteins
40
MyoD family characteristics
helix loop helix TFs forms dimer binds to E box in enhancer region of myogenic genes
41
what happens why E12 TF replaces one member of the myoD family dimer
it forms a heterodimer | binding to E box is enhanced
42
what happens when id replaces a member of MyoD dimer?
id = transcriptional inhibitor forms new heterodimer resulting in poor binding ability
43
what 2 TFs can separately activate MyoD and cause myogenic cells to become myoblasts?
Pax3 | Myf5
44
increasing levels of MyoD and Myf-5 result in ?
expression of myoblast genes by myoblasts and expression of myogenin
45
myogenin expression results in ?
expression of myotube genes and Myf-6
46
Myf-6 TF leads to ?
expression of Myofiber genes
47
actual morphogenesis of muscles is dependent on ?
associated CT framework
48
origins of epaxial trunk muscles (2)
1. epaxial = dorsal lip of myotome | 2. epaxial tendons = syndetome layer w/in somites
49
origins of hypaxial trunk muscles
muscles = ventral buds of myotomes tendons = lateral plate mesoderm
50
origins of limb muscles
muscles = ventrolateral dermomyotome tendons = lateral plate mesoderm
51
origins of muscles of head and neck
most from paraxial somitomeres extraocular muscles = prechordal plate
52
origin of cranial musculature
most = unsegmented paraxial mesoderm some/lower jaw = splanchnic mesoderm
53
origin of cranial musculature
most = unsegmented paraxial mesoderm some/lower jaw = splanchnic mesoderm
54
cardiac muscle is derived from ?
splanchnic mesoderm
55
both cardiac and skeletal muscle tissue express ?
MADS
56
how do early cardiac cells maintain their ability to divide?
by partially disassembling their contractile apparatus prior to cell division

Embryology Exam 2 (5 decks)

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