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MSK Exam I > Development Of MSK > Flashcards

Development Of MSK Flashcards

(52 cards)

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1
Q

Cells derived from the primitive node form what?

A

Paraxial mesoderm which is a thick, bilateral longitudinal column of cells along the developing NT

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2
Q

Each column of paraxial mesoderm is continuous with what?

A

Intermediate mesoderm which gradually thins into a layer of lateral mesoderm

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3
Q

What is lateral (plate) mesoderm continuous with?

A

The extraembryonic mesoderm covering the umbilical vesicle and amnion

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4
Q

Each population of mesoderm contributes to the formation of what?

A

Numerous derivatives

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5
Q

What does the intermediate mesoderm form?

A

Kidneys and gonads

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6
Q

What does the notochord develop into in the adult?

A

Intervertebral discs (nucleus pulposus)

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7
Q

What does the paraxial mesoderm form?

A

The head and somites which further differentiate into sclerotome, myotome, syndetome, dermatome and endothelial cells

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8
Q

What does the lateral plate mesoderm form?

A

Splanchnic (CVS), somatic (body cavity, pelvis, limb bones) and extraembryonic structures

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9
Q

When does the paraxial mesoderm differentiate and condense to form paired somites?

A

End of the 3rd week

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10
Q

Briefly describe somite formation

A

Formed in a craniocaudal sequence and first appear in the occipital region
39-39 pairs of somites develop initially
42-44 pairs form by the end of 5th week

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11
Q

What do somites give rise to?

A

Most of the axial skeleton and associated musculature as well as to the dermis of the skin

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12
Q

What do somites form as a result of/

A

Segmentation clock

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13
Q

Shortly after forming, each somite divides into subdivisions that give rise to what?

A

Specific mesoderm components

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14
Q

What does the ventromedial part of a somite form after undergoing EMT?

A

The sclerotome

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15
Q

What does the dorsal portion of a somite form?

A

Dermomyotome which will further divide into the dermatome and myotome

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16
Q

What does the intermediate portion of a somite form?

A

Syndetome (between sclerotome and myotome)

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17
Q

What is the sclerotome?

A

Regionalized structures that will develop into vertebrae and ribs

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18
Q

The ventral region of a sclerotome migrates to surround the notochord and forms what structure?

A

Vertebral body (central region also contributes)

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19
Q

The dorsal cells of the sclerotome that surround the NT form what structure?

A

Vertebral arch and vertebral spine

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20
Q

What do the lateral cells of the sclerotome form?

A

Transverse processes and ribs

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21
Q

Sclerotomes are divided into cranial and caudal portions due to what?

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A

Gene expression and cell density

22
Q

What divides the cranial and caudal portions of the sclerotome?

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A

Intersegmental boundary

23
Q

Describe the cranial portion of the sclerotome

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A

Loosely packed

24
Q

Describe the caudal portion of the sclerotome

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A

Densely packed

25
Describe resegmentation of the sclerotome
End of 4th week sclerotome cells appear as paired condensations around the notochord Some caudal cells move cranially and form the intervertebral disc Remaining densely packed cells fuse with the cells of the next caudal sclerotome forming the centrum Centrum develops from adjacent cranial and caudal segments and becomes an intersegmental structure Spinal nerves lie near intervertebral discs and extend from SC to innervate the myotome Intersegmental arteries lie on each side of the vertebral bodies
26
Describe intervertebral disc formation
Notochord expands to form the nucleus pulposus Nucleus pulposus becomes surrounded by caudal cells of the sclerotome which forms circularly arraigned fibers that comprise the annulus fibrosis
27
Describe development of ribs
Ribs develop from costal processes of thoracic vertebrae | Cartilaginous during embryonic period and ossify during fetal period
28
Describe development of the sternum
Paired sternal bars arise in the body wall from somatic layer of ventral plate mesoderm Located ventrolaterally and will move medially Fuse at 10 weeks to form cartilaginous models of the manubrium, sternebrae and xiphoid process
29
What do Hox genes code for?
Vertebrae identity
30
Describe Hox gene family members
Have a nested pattern of expression boundaries along cranial caudal axis These boundaries correspond to changes in vertebral shape -> changes in expression cause transformations in vertebrae
31
Which gene is important for the thoracic/lumbar boundary?
Hox10
32
What happens with loss of Hox10 paralogs?
Lumbar and sacral -> thoracic identity and have ribs
33
What occurs with a gain of Hox10 paralogs?
Thoracic vertebrae become lumbar instead
34
What are cervical ribs?
A malformation when ribs attach to cervical vertebrae (typically C7) May impinge on brachial plexus and/or subclavian artery (thoracic outlet syndrome)
35
What is pectus excavatum?
Depressed sternum and sunken posteriorly Funnel chest Underlying mechanism is extra cartilage formation of the internal aspect of the sternal bars and pulls them deeper into the eloping chest wall
36
What is pectus carinatum?
Bilateral flattening of the chest with anterior sternal protrusion Pigeon chest
37
Myogenic precursors undergo what process to form which structures?
EMT to form skeletal muscle of the trunk and limbs
38
What does myogenesis begin with?
Elongation of the nuclei and cell bodies of mesenchymal cells -> differentiate into myoblasts
39
Describe myogenesis
Mesenchymal cells differentiate into myoblasts Myoblasts fuse -> myotubes form which are elongated, multinucleated cylindrical structures Myofilaments develop in the cytoplasm of the myotubes and become invested with CT to produce fascicles
40
When do skeletal muscles develop?
Most develop before brith and almost all the remaining muscles are formed by the end of the first year
41
Each myotome divides into what?
An epimere and hypomere
42
What is the epaxial (epimere) division of the myotome?
Extensor muscles of the neck and vertebral column
43
What is the hypaxial division (hypomere) of the myotome?
Cervical, thoracic, lumbar and sacrococcygeal myotomes
44
What is the cervical myotome?
Scalene, prevertebral, geniohyoid and infrahyoid muscles
45
What is the thoracic myotome?
Lateral and ventral flexor muscles of the vertebral column
46
What is the lumbar myotome?
Quadratus lumborum
47
What is the sacrococcygeal myotome?
Pelvic floor musculature, striated muscles of anus and sex organs
48
Every spinal nerve divides to innervate what?
Trunk musculature by either dorsal or ventral ramus
49
What does the dorsal ramus supply?
Epaxial muscles
50
What does the ventral ramus supply?
Hypaxial muscles
51
What is Poland syndrome?
Absence of pectoralis minor and partial loss of pec major Ipsilateral breast hypoplasia Associated with syndactylyl or brachydacytly More frequent in males
52
What is prune bell syndrome?
Partial or complete absence of abdominal musculature Cryptorchidism (failure of one/both testes to descend) Malformation of urinary tract and bladder causing urethral obstruction and fluid accumulation that distends the abdomen causing muscle atrophy

MSK Exam I (34 decks)

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