development MSK Flashcards

(39 cards)

1
Q

What are the layers of the mesoderm? Medial to lateral

A

Notochord, Paraxial mesoderm, Intermediate mesoderm, Lateral Plate mesoderm

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2
Q

The somite comes from the paraxial mesoderm.

Name the derivatives of the somite?
What are their functions?

A
Sclerotome (cartilage)
Syndetome (tendons)
Myotome (skeletal muscle) 
Dermatome (dermis, skeletal muscle)
Endothelial cells (dorsal aorta)
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3
Q

When does paraxial mesoderm become somites?

A

End of week 3

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4
Q

How many pairs of somites are there?

A

Initially 38-39 pairs

After 5 weeks: 42-44

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5
Q

What part of somite does the SCLEROTOME come from?

A

Ventromedial part (through EMT)

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6
Q

What part of somite does the DERMOMYOTOME come from?

A

Dorsal part

It eventually splits into dermatome and myotome

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7
Q

What part of somite does the SYNDETOME come from?

A

Intermediate part

between sclerotome and myotome

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8
Q

What region of the sclerotome does the VERTEBRAL BODY come from?

A

Ventral Region

makes sense because it is closest to notochord and will wrap around

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9
Q

What region of the sclerotome does the VERTEBRAL ARCH AND SPINE come from?

A

Dorsal Cells

will surround neural tube

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10
Q

What region of the sclerotome does the TRANSVERSE PROCESS AND RIBS come from?

A

Lateral cells

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11
Q

How are sclerotomes subdivided in cranial/caudal portions?

A

Cranial= loose packed
Caudal= densely packed
Divided by intersegmental boundary (aka von Ebner’s fissure)

Due to gene expressivity and cell density

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12
Q

When do sclerotome cells condense around notochord?

A

End of week 4

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13
Q

How is a centrum formed?

A

dense (caudal) cells merge with loose (cranial) cells from next caudal sclerotome.

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14
Q

Where do intersegmental arteries lie?

A

On each side of the vertebral body

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15
Q

Why do we have 8 cervical nerves but only 7 cervical vertibrae?

A

Because the sclerotome from the occipital bone lies above C1

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16
Q

What becomes part of the nucleus pulposus?

A

The notochord. If it is not lost by adult, will form a cordoma (cancer)

17
Q

What forms annulus fibrosis?

A

the caudal cells forming circular fibers around nucleus pulposis

18
Q

When/ Where do ribs form?

A

During week 5. On costal processes of T vertebrae

cartilaginous during embryo, ossify during fetal period

19
Q

Where do sternal bars arise from?

A

somatic layer of lateral plate mesoderm

20
Q

When and in what direction do sternal bars fuse?

A

10 weeks. ventrolateral and move medially

21
Q

What axis do Hox genes code for?

A

cranial-caudal (vertebral identity)

22
Q

What gene is important at thoracic/ lumbar junction?

A

Hox10 (stops rib formation)

23
Q

What can cervical ribs cause?

A

thoracic outlet syndrom.

Impinge on brachial plexus and/ or subclavian artery –> paresthesia

24
Q

What is Pectus excavatum?

A

‘Funnel chest’
Depressed sternum, sunken posteriorly.
From extra cartilage weight
(more common in male)

25
What is Pectus carinatum?
'Pigeon chest" Sternal fusion anomoly bilateral flattening of chest with anterior protrusion
26
What is epithelial mesenchymal transformation?
Myotomes become skeletal muscles of trunk and limbs
27
How do myoblasts form?
elongation of nuclei and bodies of mesenchymal cells (if MYOD expressed)
28
Product of myoblast fusion?
Myotubes | cylindrical, multinucleated structure
29
What forms in cytoblasm of myotubes?
myofilaments
30
Myotome divide into ______ and _______?
epimere and hypomere
31
Epaxial division forms ____?
extensor muscles of necks and back. | ex: erector spinae and transversospinalis
32
Hypaxial | Cervical myotomes:
scalene, prevertebral, geniohyoid, diaphram, and infrahyoid muscles
33
Hypaxial | Thoracic myotomes:
lateral and ventral flexor ms. of vertbral column
34
Hypaxial | Lumbar myotomes
quatratus lumborum
35
Hypaxial | Sacrococccygeal myotomes:
pelvic floor ms. striated ms. of anus and sex organs
36
What innervates epaxial muscles?
Dorsal ramus
37
What innervates hypaxial muscles?
ventral ramus
38
What is Poland Syndrome?
absent pec minor, partial pec major ipsilateral migration associated with syndactyly or brachydactyly more in males
39
What is prune- belly syndrom?
Partial/complete loss of abdominal ms. distended abdomen Cryptochidism (testes don't descend) Malformation of UT and bladder