Muscular System

Question 0

myogenic cells are influenced by what?

Answer 0

signalling factors in neural tube, notochord and ectoderm

Question 1

Where are myogenic cells derived from?

Answer 1

paraxial mesoderm

Question 2

Myotubes develop as what fuse?

Answer 2

myoblasts

Question 3

How are myofibers formed?

Answer 3

from myofibrils which are produced in myotubes

Question 4

Do fibroblasts develop from this mesenchyme?

Answer 4

yes - produce CT of mm

Question 5

When does most skeletal mm develop?

Answer 5

prior to birth

Question 6

What is Epaxial division?

Answer 6

extensors of the neck and back

innervated by dorsal 1* ramus of each spinal n.

Question 7

What is hypaxial division?

Answer 7

cervicals = scalenes, prevert, geniohyoid, infrahyoids, upper limb mm.
thoracics= intercostals, abd. obliques, rectus abdominis
lumbars = QL, iliopsoas, some lower limb mm
sacral = pelvic diaphragm, sphincters, some lower limb mm
- innverated by ventral 1* ramus of spinal n.

Question 8

How are myotome fibers oriented originally?

Answer 8

craniocaudally

Question 9

Can a myotome split?

Answer 9

yes - drags n with it and forms 2 separate mm

Question 10

how are non segmental trunk mm formed?

Answer 10

derived from myotomes at multiple levels that fuse together

Question 11

What happens when a mm degenerates?

Answer 11

forms CT sheets or aponeurosis

Question 12

What does splanchnic mesoderm of smooth mm. give rise to?

Answer 12

mm layers in gut derivatives

Question 13

What does somatic mesoderm of smooth mm give rise to?

Answer 13

tunica media of blood vessels and lymphatics

Question 14

What is special about smooth mm?

Answer 14

• cells differentiate but dont fuse together
• form sheets or bundles of cells
• acquire autonomic innervation
• produce collagen and elastic fibers

Question 15

What does splanchnic mesoderm of cardiac mm give rise to?

Answer 15

cardiac myoblasts

Question 16

What forms when cardiac myocytes come in contact?

Answer 16

intercalated discs

Question 17

What are some skeletal mm anomalies?

Answer 17

• variation in form, position and/or attachment
• accessory mm develop occasionally
• absence of one or more mm
  
  • more common bilaterally

Question 18

What is arthrogyroposis multiplex congenital?

Answer 18

• congenital stiffness of 1+ joints
• due to hypoplasia of assoc. mm.
• mm replaced by fat and fibrous CT

Question 19

What is torticollis?

Answer 19

unilateral shortening of SCM
- head lat. flex and look up and away from affected side
myofibers die and replaced by fibrous CT