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Flashcards in Development of Muscular System Deck (24)
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1

What is skeletal muscle derived from?

Paraxial mesoderm

2

What is cardiac and visceral smooth muscle derived from? 

Splanchnic Mesoderm 

3

What is vascular smooth muscle derived from? 

Local Mesenchyme 

4

What developmental anatomy do the skeletal muscles of truck and limbs originate from?

Somites 

5

What part of the somite does the dermomyotome derive from? 

The dorsolateral or dorsal part of the somite under the influence of Wnts

6

What part of the dermatomyotome undergoes an epithelial to mesechymal transformation? And what happens when this occurs?

The dorsomedial and dorsolateral edges

They become myogenic -- called Myotome  

7

What is the myotome a precursor for? 

For skeletal muscle of the trunk and limbs 

8

What regulatory factors form the intrinsic muscles of the back? What domain is this? 

Myf5 and MyoD

 

Primaxial domain 

9

What myogenic regulatory factor induces the muscles of the abdominal walla nd the limbs of the infrahyoid muscles? What domain is this? 

MyoD

 

Abaxial domain 

10

What happens after myogenic cells become comitted byoblasts? 

They being to synthesize actin and myosin

They reach their definitive location in the embroy and secrete adhesive glycoprotein, fibronectin. 

They align in chains of myoblasts -- which fuse to become multinucleated myotubes (requires M-cadherin) 

11

What mediates myofiber and sarcomere formation? 

Troponin and tropomyosin

Create a differentiated muscle cell/muscle fiber

12

When is skeletal muscle fiber formatino completed?

At birth!

13

What accomplishes myogenic postnatal growth of skeletal muscle? What mediates their expression? 

Myogenic stem cells -- satellite cells 

 

Pax 3 and Pax 7

14

What are some proposed strategies for the formatin of individual skeletal muscles? 

  • Change in fiber direction
  • Fusion of adjacent myotomes
  • Longitudinal splitting
  • Tangential splitting into layers
  • Atrophy of a part
  • Migration 

15

How do skeletal muscles become innervated?

Myotome is divided into Epaxial (dorsal) and Hypaxial (ventral) portions 

 

Epaxial portion of myotome (intrinsic muscles of back) receives motor innervation from dorsal primary rami. 

Hypaxial portion of dermatome (ventrolateral body wall and limb muscles) receives motor innervation from ventral primary rami. 

16

What are the master regulators of smooth muscle gene expression?

Serum Response Factor (SRF) 

Myocardin

17

What does smooth muscle orignate from? 

Splanchnic mesoderm 

18

What are smooth muscles able to do postnatally? 

Divide in response to extracellular signals

19

What is cardiac muscle derived from?

Splanchnic mesoderm of the primary and secondary heart fields

20

What transcription factors regulat cardiac myocyte formation? 

GATA 4 & 6, Foxp1, Nkx2.5 and twist 

Also BMP and FGF

21

What is muscular dystrophy? 

Family of genetic diseases exhibiting progressive weakness and deterioration of skeletal muscle cells without CNS or peripheral nervous pathology 

 

Duchenne Type: most common, x-linked recessive, affects boys in early childhood, myocytes lack dystrophin 

 

Becker's Type: later onset and milder condition

22

What is congenital torticollis? 

Fixed rotation and tilting of the head to one side

More common on rights side

May have congential hip dysplasia too

23

What is Prune Belly Syndrome?

Three defects: 

1) absence of abdominal muscles

2) undescended testicles

3) bladder and urinary tract abnormalities 

 

Prenatal accumulation of fluid in the lower abdomen due to urinary system snomalies may interfere with devo or cause degen of ab muscles 

24

What is Poland Sequence? 

Characterized by absence of pectoralis major and the pectoralis minor muscles 

Nipple on that side is displaced laterally or missing 

Rib cage hypoplastic, Upper limb anomalies -- shortened limb segments and hand defects (syndactyly and brachydactyly) 

Twice as common on right side, and more prevalent in males