Development of the musculoskeletal system Flashcards

1
Q

What embryonic germ layer is skeletal muscle derived from?

A

Paraxial mesoderm

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2
Q

Where are the epaxial muscles located and what do they form upon maturation?

A

They are dorsal to the transverse processes and form the intrinsic muscles of the back

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3
Q

What line do myotomes originate from?

A

Somites

Formed by the cells at the ventrolateral lip (VLL) of the prospective myotome region and by cells from the dorsomedial lip (DML)

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4
Q

What portion of the mesoderm do VLL contribute cells to?

A

Cells at the ventrolateral lip contributes cells to both the primaxial and abaxial domains of the mesoderm

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5
Q

What portion of the mesoderm do DML contribute cells to?

A

Cells at the dorsomedial lip contribute to the primaxial domain of the mesoderm (also includes sclerotome and dermatome cells)

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6
Q

What cells does the primaxial domain contain? What does this domain form?

A

Cells from the paraxial mesoderm.

Forms muscles of the back, shoulder girdle (rhomboids, levator scapulae, and latissimus dorsi), and intercostals

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7
Q

What cells form dermis on the back (from dermatomes), vertebrae, and bony parts of the ribs (from sclerotome)?

A

Paraxial cells

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8
Q

What does the abaxial domain form?

A

Limb and abdominal wall (obliques and transversus abdominus muscles)

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9
Q

What do abaxial cells form?

A

The dermis in the body wall (from lateral plate mesoderm) and rib cartilages (from sclerotome cells that migrate across the lateral somitic frontier)

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10
Q

Where do migrating muscle cells receive innervation from?

A

Their spinal segments of origin - migrating muscle cells carry these spinal nerves with them as they migrate

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11
Q

What molecular regulation is important for the formation of skeletal muscle?

A

WNT, MyoD, BMP4 with low SHH

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12
Q

Describe the patterning of the muscles in the head

A

Head musculature formed by somitomeres - tongue, eye (except those of the iris = pupillary muscles = derived from the optic cup) and pharyngeal arches.

Muscles in the head are patterned by connective tissue that is formed by neural crest

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13
Q

Describe the patterning of the muscles of the limb:

A

Limb muscles formed by VLL cells: patterned by connective tissue formed by lateral plate mesoderm regulated by MyoD genes (transcription factor)

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14
Q

Describe the formation of cardiac muscle:

A

Derived from visceral mesoderm surrounding heart tube
Intercalated discs
Purkinje fibers

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15
Q

Describe the formation of smooth muscle:

A

Embryonic derivative of visceral layer of lateral plate mesoderm, some neural crest cells for sphincter and dilater

Molecular commitment — SRF, MRTFs

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16
Q

Paraxial mesoderm forms ________ along the spinal cord and somitomeres in the head.

A

Somites

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17
Q

What are the three components of somites?

A

Dermatome (skin)

Myotome (muscle)

Sclerotome (bone)

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18
Q

What is mesenchyme tissue?

A

Mesenchyme tissue = any loose connective tissue regardless of origin (i.e. neural crest cells)

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19
Q

List the parts of the neurocranium:

A

Membranous (membranes - intramembranous ossification)

Condrocranium

Sutures

20
Q

List the parts of the viscerocranium

A

Face

Mostly from the frontonasal prominence and the 1st and 2nd pharyngeal arches - neural crest cells

1st arch = maxilla, mandible, malleus, incus

2nd arch - stapes, part of hyoid bone

21
Q

When do the limb buds form?

A

During the 4th and 5th weeks

22
Q

What specifies the location and type (forelilmb/hindlimb) of limb budding?

A

HOX genes location

TBX5 specifies forelimb structures

TBX4 specifies hindlimb structures

23
Q

AER

A

Apical ectodermal ridge - proximodistal growth - FGF’s maintain a rapidly proliferating population of cells adjacent to the ridge - the progress zone

24
Q

ZPA

A

Zone of polarizing activity - cranial to caudal (anterior-posterior) patterning, thumb to little finger - SHH and retinoic acid - morphogens

25
Q

How do the digits separate during development?

A

Cell death in ridge

26
Q

What determines bone patterning

A

HOX genes

27
Q

What clinical issues are associated with limb development?

A

Amelia - no limbs

Meromelia - short limbs

Talidomide - limb defects, now an anticancer and anti AIDS drug so we are seeing these limb defects again

syndactyly - fused digits

brachydactylly - short digits

28
Q

What is the vertebral column derived from?

A

Somites (slerotome) and notochord (nucleus pulposus)

Caudal part of one clerotome fuses with cranial part of another - intersegmental so that muscles bridge the vertebra to act on them - resegmentation

29
Q

What are the two major parts of the skull?

A

The viscerocranium (face)/Neurocranium(flat bones of the skull from paraxial mesoderm)

30
Q

What do the hypaxia muscles form?

A

Muscles in the body wall

31
Q

Anywhere there is segmentation in the embryo there are ____ genes:

A

HOX

32
Q

What upper limb muscles are derived from the VLL that migrate across the lateral somitic frontier?

A

All distal limb muscles

33
Q

What muscles do the primaxial cells give rise to?

A

The extrinsic and intrinsic back muscles

34
Q

What gives rise to the spinal ganglia?

A

The neural crest cells (ganglia composed of cell bodies)

35
Q

What do abaxial/sclerotome form when they cross the lateral somitic frontier?

A

The ribs

36
Q

What is the relationship between homebox and HOX genes?

A

All HOX are homeobox genes, not all homeobox are HOX

37
Q

How do vertebrae form from somites?

A

The caudal half of one fuses with the cranial half of another.

This process is called resegmentation

38
Q

What cell population is responsible form forming the neurocranial region?

A

Paraxial mesoderm

39
Q

What cell population is responsible for forming the viscerocranial region?

A

Neural crest cells

40
Q

What cell population is responsible for forming the chordal chondrocranium?

A

The paraxial mesoderm

41
Q

What cell population is responsible for forming the viscero chondrocranium?

A

Neural crest cells

42
Q

What causes craniusynostosis and achondroplasia?

A

Mutations in the fibroblast growth factor receptors (FGFRs)

43
Q

What is SALL4?

A

Transcription factor that regulates FGF. Drugs that interfere with SALL4 during embryogenesis cause birth defects where the fetus has shortened limbs.

44
Q

What gene misregulation causes polydactyly?

A

SHH

45
Q

What is responsible form the location of limb bud formation?

A

The HOX genes

FGF 10 is expressed in the lateral mesoderm that induces limb bud growth

46
Q

What growth regulation factors does the apical ectrodermal ridge secrete?

A

FGF4 and FGF8

The flank mesoderm initiates limb outgrowth and causes the AER

47
Q

Where and what is the zone of polarizing activity?

A

The ZPA secretes SHH and specifies anterior-posterior patterning (i.e. thumb to little finger)