DEVO Flashcards

1
Q

What is the initial progenitor tissue of all musculoskeletal tissues?

A

mesenchyme (STFM)

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2
Q

The STFM that eventually forms the vertebrae and ribs is derived from which precursor mesenchyme?

A

Scleratome tissue of the somites

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3
Q

The STFM that eventually forms the sternum is derived from which precursor mesenchyme?

A

Somatic mesoderm of the ventral body wall

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4
Q

The appendicular skeleton is derived from____?

A

somatic mesoderm

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5
Q

When they receive inductive signals, what does skeletal precursor mesenchyme change into?

A

Preskeletal mesenchyme condensations (inductive signals are often from the adjacent epithelium

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6
Q

What is the bone master gene?

A

RunX-2

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7
Q

What is the cartilage master gene?

A

Sox9

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8
Q

During endrochondral ossification, what TXF stimulates cells of the perichondrium to express Runx2 and differentiate into OBs?

A

Ihh (Indian hedgehog)

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9
Q

During endochondral ossification, some chondrocytes hypertrophy and express what?

A

Type X collagne and VEGF

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10
Q

Runx2 is also know as?

A

CBFA-1

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11
Q

a cell that expresses Runx2 will become an ______?

A

Osteoblast

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12
Q

a cell that expresses Sox-9 will become a _______?

A

Chondroblast

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13
Q

the amount of epiphyseal cartilage retained in the skeleton is the _________.

A

Bone age

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14
Q

a radiologist determines bone ate by what two criteria?

A
  1. appearance of calcified material in the diaphysis and/or epiphysis for each bone and sex
  2. the disappearance of the dark line representing the epiphyseal cartilage plate indicates that teh epiphysis is closed (usually R hand and wrist are used)
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15
Q

Achondroplasia is d/t ?

A

mut in the FGF-R3 gene that affects cartilage formation

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16
Q

characteristics of an achondroplastic dwarf

A
shortened skull base
shortened limbs
lordosis
normal trunk size
normal mental status
generally no skeletal or ear anomalies
new mutation or AD
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17
Q

Pituitary dwarfism is d/t

A

interrupted bone growth d/t insufficient production of GH

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18
Q

cretinism is associated with

A

advanced paternal age

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19
Q

cretinism is d/t

A

deficiency of thyroid hormone

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20
Q

in which type of dwarfism is the skeletal age less than the actual age?

A

cretinism

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21
Q

How does mucopolysaccharidoses affect skeletal development?

A

LSD&raquo_space; no degradation of proteoglycans
» distortion of face and skull
» ocular and CNS anomalies as well

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22
Q

osteogenesis imperfecta is d/t

A

defect in type I collagen

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23
Q

how does osteogenesis imperfecta present?

A
blue sclera
brittle bones, many fractures
hearing loss
growth restriction
kyphosis
macorcephaly
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24
Q

How does the sclerotome form?

A

during somite differentiation, the neural tube and notochord produce Shh (and others), which induces the ventral half of the somite to undergo EMT (sclerotome includes the somitocoel cells)

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25
Q

What does the sclerotome become?

A

migrate medially to become the vertebral column and ribs

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26
Q

describe the cranial-caudal compartmentalization of the sclerotome

A

Resegmentation:
cranial = loose
caudal = dense
divide and fuse, causing muscles to span two vertebrae and spinal nerves to grow across the interface

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27
Q

which sclerotome compartment becomes the vertebral body?

A

ventral

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28
Q

which sclerotome compartment becomes the neural arch and spinous process?

A

dorsal

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29
Q

which sclerotome compartment becomes the distal rib?

A

lateral

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30
Q

which sclerotome compartment becomes the pedicle and proximal rib?

A

central

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31
Q

what part of the sclerotome becomes the IV disc, vertebral joints and proximal rib?

A

somitocoel cells

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32
Q

What structures allow a vertebra to grow?

A

a piece of cartilage remains between each neural arch and centrum (NEUROCENTRAL JUNCTION), allowing for longitudinal growth

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33
Q

what controls axial patterning of the vertebrae?

A

differential expression of Hox genes along the axis of the embryo&raquo_space; cranial-caudal patterning
Also, signals from the notochord and spinal ganglia control dorsal-ventral patterning

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34
Q

characteristics of Klippel Feil sequence

A

short neck, low hair line, restricted back movements
number of cervical vertebrae is less than normal
many other defects: undescended scapula, cervical rib, scoliosis, UG, CNS, cardiopulmonary, hand, and hearing

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35
Q

Klippel Feil is d/t

A

defect in Hox gene expression d/t abnormal retionic acid expression

36
Q

describe spina bifida

A

failure of fusion of the halves of the vertebral arch

37
Q

hemivertebrae

A

results from failure of one of the chondrification centers of the centrum to form
results in wedge shaped vertebrae&raquo_space; scoliosis

38
Q

term used when many vertebrae have unfused spinous processes

A

rachischisis

39
Q

sternal clefts are d/t

A

abnormal fusion of the sternal bars in the midline
> convex = precuts excavate
> concave = precuts cranium

40
Q

skeletal muscle is derived from

A

paraxial mesoderm&raquo_space; myotome tissue of the somites

41
Q

visceral smooth muscle is derived from

A

splanchnic mesoderm

42
Q

vascular smooth muscle is derived from

A

local mesoderm and neural crest ectomesenchyme

43
Q

cardiac muscle is derived from

A

splanchnic mesoderm of heart fields

44
Q

describe the formation of the dermomyotome

A

under the influence of Wnt from the surface ectoderm, the dorsal half of the somite remains an epithelium and is call the DM

45
Q

Wnt and Shh influence the cells of the medial DM to do what?

what happens to the lateral cells?

A

EMT and migrate beneath the remaining epithelial cells of the DM
The lateral DM is influenced by bmp, undergoes EMT as well and migrates underneath the DM epithelium
all these mesenchymal cells become myogenic cells

46
Q

what do myogenic cells express?

A

Myogenic regulatory factors Myf5 and MyoD

47
Q

what is the lateral somite frontier?

A

between the paraxial and lateral mesoderms
> an interface created by the opposing gradients of signaling molecules from the lateral mesoderm and the dorsal neural tube

48
Q

what is on either side of lateral somite frontier?

A
medial = primaxial domaine >> intrinsic back muscles
latera = abaxial domaine >> adominals, intercostals, distal limb muscles, all LL muscles
49
Q

once myogenic cells proliferate and migrate, they are called _____ and are post-mitotic

A

myoblasts

50
Q

myoblasts fuse and become _______

A

multinucleated myotubes, which further differentiate into primary muscle fibers

51
Q

describe secondary muscle fibers

A

form later in development and are external to primary fibers. some suggest these become fast fibers (primary are slow fibers)

52
Q

epaxial muscles are innervated by which primary rami

A

dorsal

53
Q

hypaxial muscles are innervated by which primary rami

A

ventral

54
Q

what is a body wall segment?

A

section of embryo representing a spinal cord level (skin, muscle, nerve pair

55
Q

when does the coordination of innervating body wall segments occur?

A

embryonic period, early in prenatal development

56
Q

a defect in the SCM muscle causes what?

A

congenital torticollis

57
Q

what is prune belly syndrome

A

absent abdominal wall muscles

> often associated with bladder anomalies and UT obstruction

58
Q

what is poland sequence

A

absence of pec major and minor

59
Q

expression of what localizes limb fields at distinct axial levels?

A

Hox genes

60
Q

What specific TXF is expressed within the UL

A

Tbx5

61
Q

intermediate mesoderm sends signals and in appropriate areas, the lateral plate mesoderm expresses what to induce limb bud outgrowth

A

FGF 10

62
Q

somatic mesoderm forms…

A

skeletal elements
fibrous CT
dermis

63
Q

somitic mesoderm forms

A

skeletal muscle

64
Q

muscles and nerves are organized in compartments along a ______________ axis

A

dorsal-ventral

65
Q

digits are arranged along a _____________ axis

A

AP

66
Q

which growth factor causes the distal limb ectoderm to turn into the AER?

A

FGF 8, stimulated by FGF 10

67
Q

the AER secretes FGF-8 to keep a pool of undifferentiated mesenchyme available for limb elongation. What does this mesenchyme secrete to maintain the AER?

A

FGF-10 (positive feedback loop)

68
Q

what does the ZPA secrete?

A

Shh

69
Q

What does Shh from the ZPA do?

A

initiates expression of a Hox gene subset in an overlapping nested fashion
responsible for digit formation

70
Q

what is the role of apoptosis in limb development?

A

digit separation

71
Q

by week ____ the limbs have rotated

A

8

72
Q

what is the frequency of limb anomalies?

A

2/1000 live births

73
Q

when is limb development most sensitive to teratogens?

A

4th to 9th weeks

74
Q

what is the difference between a defect and a deformity

A
defect = abnormal development >> morphological abnormality
deformation = abnormal form, shape or position of a normally formed body part CAUSED BY MECHANICAL FORCES DURING DEVO
75
Q

term for absence of an entire limb

A

amelia

76
Q

term for absence of part of a limb

A

meromelia

77
Q

oligodactyly

A

LONGITUDINAL failure of limb formation in which median digits are missing&raquo_space; lobster claw

78
Q

phocomelia

A

LONGITUDINAL failure of limb formation where the most distal limb segments are attached directly to the limb girdle

79
Q

syndactyly

A

failure of differentiation/separation of digits

80
Q

Sirenomelia

A

fusion of lower limbs

81
Q

what is the major developmental problem involved in clubfoot?

A

defect involving the talas bone

82
Q

is clubfoot more common in M or F?

A

M

83
Q

cause of developmental hip dysplasia?

A

insufficiently formed hip joint

84
Q

sprengel deformity?

A

undescended scapula at C4-T2 (normally T2-T7)

3x > M

85
Q

Cleidocranial dysplasia

A
Defect in RunX-2
variety of anomalies:
hypoplasia/aplasia of clavicles
large head
small face
long neck
short narrow chest