Development of Muscular System Flashcards Preview

MSS > Development of Muscular System > Flashcards

Flashcards in Development of Muscular System Deck (24)
Loading flashcards...

What is skeletal muscle derived from?

Paraxial mesoderm


What is cardiac and visceral smooth muscle derived from? 

Splanchnic Mesoderm 


What is vascular smooth muscle derived from? 

Local Mesenchyme 


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



What part of the somite does the dermomyotome derive from? 

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


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  


What is the myotome a precursor for? 

For skeletal muscle of the trunk and limbs 


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

Myf5 and MyoD


Primaxial domain 


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



Abaxial domain 


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) 


What mediates myofiber and sarcomere formation? 

Troponin and tropomyosin

Create a differentiated muscle cell/muscle fiber


When is skeletal muscle fiber formatino completed?

At birth!


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

Myogenic stem cells -- satellite cells 


Pax 3 and Pax 7


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 


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. 


What are the master regulators of smooth muscle gene expression?

Serum Response Factor (SRF) 



What does smooth muscle orignate from? 

Splanchnic mesoderm 


What are smooth muscles able to do postnatally? 

Divide in response to extracellular signals


What is cardiac muscle derived from?

Splanchnic mesoderm of the primary and secondary heart fields


What transcription factors regulat cardiac myocyte formation? 

GATA 4 & 6, Foxp1, Nkx2.5 and twist 

Also BMP and FGF


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


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


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 


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