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MSK Test 1 > LEC-3 MSK Embryology > Flashcards

LEC-3 MSK Embryology Flashcards

1
Q

The mesoderm for the skeletal system comes from what two sources?

A
  • Paraxial mesoderm
  • Parietal mesoderm
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2
Q

The skeletal system is formed from what two embryonic tissues?

A
  • Mesoderm tissue
  • Neural crest tissue
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3
Q

Somitomeres and somites are formed from which mesoderm?

A

Paraxial

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4
Q

Which mesoderm becomes fused to the body wall once folding of the embryo occurs?

A

Parietal

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5
Q

What two signal transduction pathways regulate the differentiation of mesenchymal cells into sclerotome, or cells that form the vertebral arch?

A
  • SHH (Sonic Hedgehog)
  • Noggin
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6
Q

Cells at the ____________ and _____________ tips of a developing somite differentiate into precursor muscle cells, known as the _________.

A
  • Dorsomedial and ventrolateral.
  • Myotome
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7
Q

Cells intervening between the ventrolateral and dorsomedial tips of the developing somite differentiate into precursor skin cells known as the ______________.

A

Dermatome

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8
Q

_________ and _________ are two key encoding genes that produce proteins vital for muscle differentiation in developing embryos.

A

MyoD and MYF5

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9
Q

In general, what forms the face and part of the skull?

A

Neural crest

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10
Q

In general, what forms the axial skeleton from somites and part of the skull from somitomeres and occipital somites?

A

Paraxial mesoderm

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11
Q

In general, what forms the limbs, sternum, and the pelvic and shoulder girdles?

A

Parietal mesoderm (body wall)

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12
Q

What are somitomeres and somites?

A

The segmentally arranged clusters of cells derived from mesoderm and located along the axis of the developing embryo

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13
Q

(Somites/Somitomeres) are located from the occipital region to the coccyx in the developing embryo. They are small and tightly organized.

A

Somites

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14
Q

(Somites/Somitomeres) are located in the head region of the developing embryo. They are large and loosely organized.

A

Somitomeres

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15
Q

The vault of the skull refers to the (chondrocranium/membranous neurocranium/viscerocranium).

A

Membranous neurocranium

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16
Q

Through what method is the neurocranium formed?

A

Formed through direct intramembranous ossification (meaning cartilage is not present during ossification).

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17
Q

The face refers to the (chondrocranium/membranous neurocranium/viscerocranium).

A

Viscerocranium

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18
Q

Through what method is the viscerocranium formed?

A

Formed by endochondrial ossification (meaning cartilage is present during ossification) AND intramembranous ossification (meaning cartilage is not present during ossification)

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19
Q

The base of the skull refers to the (chondrocranium/membranous neurocranium/viscerocranium).

A

Chondrocranium

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20
Q

Through what method is the chondrocranium formed?

A

Formed by endochondrial ossification (meaning cartilage is present during ossification).

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21
Q

Identify which of the following structures are derived from the neural crest.

A

Neural crest structures are shown in blue.

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22
Q

Identify which of the following structures are derived from the paraxial mesoderm.

A

Paraxial mesoderm structures are shown in red.

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23
Q

Identify which of the following structures are derived from the parietal mesoderm.

A

Parietal mesoderm structures are shown in yellow.

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24
Q

Identify which of the following structures are derived from the paraxial mesoderm.

A

Paraxial mesoderm structures are shown in red.

  • Base of skull = Chondrocranium
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25
Q

Identify which of the following structures are derived from the neural crest.

A

Neural crest structures are shown in blue.

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26
Q

(T/F) The membranous neurocranium is derived from mesenchyme that originates from the neural crest and paraxial mesoderm. Its bone is formed as mesenchyme first differentiates into hyaline cartilage. Blood vessels then invade the cartilage, allowing osteoblasts to differentiate and form the bone.

A

False. The neurocranium is formed from intramembranous ossification. The process described was endochondrial ossification. Neurocranium is formed from mesenchyme differentiating directly into bone. Bony spicules begin to grow outward from a primary ossification site toward the periphery. Bone growth is then continued by appositional (layering) addition of bone on the outer surface and osteoclast resorption from the inside.

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27
Q

Describe endochondrial ossification.

A
  1. Surrounding mesenchyme differentiates into hyaline cartilage, forming an “outline”.
  2. Blood vessels invade the cartilage.
  3. Osteoblasts differentiate in the area and form bone.
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28
Q

Describe intramembranous ossification.

A
  1. Mesenchyme differentiates into primary ossification center.
  2. Bony spicules grow from primary ossification center towards periphery.
  3. Bone growth is continued through appositional addition of new layer on outer surface and osteoclast resorption from inside.
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29
Q

What type of ossification forms most bones in the face?

A

Endochondrial ossification

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30
Q

What type of ossification forms the mandible?

A

Intramembranous ossification

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31
Q

What are the first bones to fully ossify in the head?

A

Ossicles (malleus, incus, and stapes)

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32
Q

___________ are narrow seams of connective tissue between two bones.

A

Sutures

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33
Q

What suture is derived from the paraxial mesoderm?

A

Coronal

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34
Q

What suture is derived from the neural crest?

A

Sagittal

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35
Q

(T/F) While forming, sutures are relatively safe and stable.

A

False. Sutures are highly susceptible to teratogens throughout the differentiation and ossification process. Severe malformations may occur if the sutures become adversely affected by teratogenesis.

36
Q

Where do fontanelles form and what do they allow?

A
  • Form where two sutures meet.
  • Allow bones to overlap during birth and then return to original position.
37
Q

What fontanelle usually closes by 18 months of age and can be palpated to asses skull ossification and intracranial pressure?

A

Anterior fontanelle

38
Q

Palpating the anterior fontanelle of a child is done to asses?

A
  • Skull ossification
  • Intracranial pressure
39
Q

_____________ is caused by the failure of the anterior neuropore to close. This results in subsequent failure of the cranial vault to fully form and brain degeneration results, ending with anencephaly. This condition is lethal.

A

Cranioschisis

40
Q

______________ or _________________ refer to small defects in skull formation which allow the meninges or brain tissue to herniate. The extent of neurological defects caused by this condition depend upon the degree of brain tissue damage.

A

Meningocele or meningoencephalocele

41
Q

______________ is the premature closure of one or more sutures during cranial differentiation and formation.

A

Craniosynostosis

42
Q

Craniosynostosis involves the altered activity of what proteins?

A
  • FGF-R (Fibroblast growth factor receptor)
  • TGF-β (Transforming growth factor β)
  • MSX2
  • TWIST1
43
Q

_____________ is the result of abnormal growth of the skull base. It is caused by the premature closure of the sagittal, coronal, and lambdoid sutures.

A

Cloverleaf skull

44
Q

What is responsible for the formation of the vertebral arches, vertebral body, spinous process, and transverse process.

A

Sclerotome

45
Q

Spina bifida (occulta/cystica) is the often undetected failure of some part of the vertebrae to fully close. It is the most mild form of spina bifida and occurs in up to 10% of the population. There are usually no clinical consequences as the spinal cord and meninges both remain intact. The defect is most often covered by skin or, in some cases, a patch of hair.

A

Occulta

46
Q

Spina bifida (occulta/cystica) occurs when portions of the neural tube fail to close, vertebral arches fail to form, and neural tissue becomes exposed. This condition may be detected by ultrasound and elevated levels of α-fetoprotein in the amniotic fluid.

A

Cystica

47
Q

Supplementation with _____________ before and during pregnancy has been shown to greatly reduce the risk of neural tube defects such as spina bifida and other malformations.

A

Folic acid

48
Q

Describe the resegmentation of sclerotome to form the vertebrae.

A
  1. The caudal half of each sclerotome grows into and fuses with the cephalic half of each subjacent (below) sclerotome.
  2. The resulting space left between vertebral bodies forms the intervertebral (IV) discs.
  3. Notochord regresses to remain within the IV disc where it contributes to the nucleus pulposus.
  4. Myotome does not resegment and now spans the IV discs.
  5. Spinal nerves innervate each myotome and are near the IV discs, passing through the IV foramina.
  6. Intersegmental arteries originally in mesenchyme between blocks of segmented sclerotome are positioned over vertebral bodies.
49
Q

______________ may develop due to improper resegmentation of the sclerotome during formation of the vertebra.

A

Scoliosis

50
Q

The (sternum/clavicle/ribs) is/are formed from sclerotome cells that remain in the paraxial mesoderm by endochondrial ossification. It/They occur as growth(s) from the vertebra.

A

Ribs

  • Grow from costal processes leaving the vertebra
51
Q

The (sternum/clavicle/ribs) is/are formed from parietal mesoderm via intramembranous ossification.

A

Clavicle

52
Q

The (sternum/clavicle/ribs) is/are formed from parietal mesoderm via endochondrial ossification. Fusion occurs at the midline, and failure of structure-specific bands may result in a cleft.

A

Sternum

  • Failure to fuse sternal bands results in cleft sternum
53
Q

(T/F) The outgrowth of mesenchyme from the body wall serves to form the appendicular skeleton.

A

True.

54
Q

The outgrowth of the appendicular skeleton proceeds in what direction?

A

Cranial to caudal direction

55
Q

The position of outgrowth on the craniocaudal axis is defined by the ______ gene pattern.

A

Hox

56
Q

Limb bud outgrowth from the ventrolateral body wall is stimulated by the proteins ____ and ____.

A

FGF and TBX

57
Q

The apical ectodermal ridge (AER) forms in ectoderm at the distal border of the limb bud under the influence of ______ and _____.

A

BMP and HOX

58
Q

As AER moves distally, mesenchyme located more proximally undergoes differentiation and condensation to form __________.

A

Cartilage

59
Q

The secretion of ____ by the AER serves to drive proximal to distal limb growth.

A

FGF

60
Q

The _________________ is a region of highly proliferative mesenchyme located just medially to the apical ectodermal ridge.

A

Progress zone

61
Q

The AER (prohibits/maintains) proliferation in the progress zone.

A

Maintains

62
Q

The AER maintains proliferation in the progress zone through secretion of ____.

A

FGF

63
Q

The AER (prohibits/maintains) differentiation in the progress zone.

A

Prohibits

64
Q

The _______________________ is located at the posterior border of the apical ectodermal ridge, moving distally as the limb grows. It expresses retinoic acid (RA) that induces the expression of the SHH protein.

A

Zone of polarizing activity (ZPA)

65
Q

Release of retinoic acid and expression of the SHH protein are highest where (anterior/posterior) structures are formed on the limbs.

A

Posterior

  • At ZPA (retinoic acid induces expression of SHH)
66
Q

_______ genes regulate the type and shape of limb bones.

A

Hox (Homeobox)

67
Q

Expression of Hox is regulated by ______, ______, and ______.

A

SHH, FGF, and WNT

68
Q

The bone and cartilage of the limbs forms from the (neural crest/paraxial mesoderm/parietal mesoderm).

A

Parietal mesoderm

69
Q

The bone and cartilage of the limbs forms through (endochondrial/intramembranous) ossification.

A

Endochondrial

70
Q

During the 7th week of embryonic development, upper limbs rotate 90° (laterally/medially).

A

Laterally

71
Q

During the 7th week of embryonic development, lower limbs rotate 90° (laterally/medially).

A

Medially

72
Q

The upper limb is innervated by ventral primary rami of levels ___ - ___.

A

C5 - T2

73
Q

The lower limb is innervated by ventral primary rami of levels ___ - ___.

A

L2 - S2

74
Q

____________ is the most common form of skeletal dysplasia that results in defects of growth in long bones, digits, skull, and the face, along with accentuated spinal curvature.

A

Achondroplasia

75
Q

Achondroplasia is the result of mutations in ______.

A

FGF-R

76
Q

____________ is the milder form of achondroplasia that is without the craniofacial features.

A

Hypochondroplasia

77
Q

The complete lack of one or more limbs at birth is referred to as ___________.

A

Amelia

78
Q

The birth defect characterized by lacking part, but not all, of a limb is known as __________.

A

Meromelia

79
Q

A birth defect marked by uncommonly short digits is known as ______________.

A

Brachydactyly

80
Q

A birth defect marked by the fusion of digits is known as ________________. This condition may also be associated with clubfoot.

A

Syndactyly

81
Q

A birth defect marked by the presence of extra digits is known as ______________.

A

Polydactyly

82
Q

A disruption of the AER or a vascular deformation during embryonic development may result in _____________________

A

Transverse limb deficiency

83
Q

What are both cardiac and smooth muscle derived from?

A

Visceral mesoderm

84
Q

What is skeletal muscle derived from?

A

Paraxial mesoderm

85
Q

What myogenic regulatory factors are expressed in the ventrolateral edge of the dermomyotome?

A

Myo-D

86
Q

What myogenic regulatory factors are expressed in the dorsomedial edge of the dermomyotome?

A

Myo-D and MYF

87
Q

_____________ results from the partial or complete absence of abdominal wall musculature.

A

Prune belly syndrome

MSK Test 1 (11 decks)

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