10-1a. 3rd and 4th Layers - Conference

Question 1

flexor hallucis brevis:

origins and insertions

Answer 1

• origin: y-shaped tendon
  
  • medial arm: slip from tibialis posterior tendon
  • lateral arm: cuboid and lateral cuneiform
• insertion:
  
  • main: HPP base on each side
  • minor: sesamoids, plantar MTP ligament, extensor expansion

Question 2

flexor hallucis brevis:

innvervation and major actions

Answer 2

inn: medial plantar nerve

act: plantarflexes MTPJ 1

Question 3

adductor hallucis:

origins & insertions

Answer 3

• origin:
  
  • oblique head: peroneal sheath, bases and shafts of MT 2-4
  • transverse head: fibrous capsule & plantar MTP ligaments of toes 3-5; deep transverse MT ligament
• insertion:
  
  • major: tendons of both heads attach to the lateral side of HPP base (like FHB)
  • minor: lateral sesamoid; plantar MTP ligament and extensor expansion

Question 4

adductor hallucis:

innervation and actions

Answer 4

• inn: lateral plantar nerve (Deep branch)
• actions: adducts first digit

Question 5

flexor digiti minimi brevis:

origins and insertions

Answer 5

• origin
  
  • promontory of cuboid, peroneal sheath, MT 5 base
• insertion:
  
  • MTPJ capsule, extensor expansion, MT5 head and PP5 base

Question 6

flexor digiti minimi brevis:

innervation, and actions

Answer 6

inn: Lateral plantar nerve (superficial branch)
act: plantarflexes MTPJ 5 and can also abduct the 5th toe

Question 7

which muscle is formed when some fibers of FDMB distinctly insert onto lateral aspect of MT 5?

Answer 7

opponens digiti minimi

Question 8

2 intrinsic and 2 extrinsic muscles of 4th compartment

Answer 8

Intrinsic:

• tibialis posterior & fibularis longus

extrinsic:

• dorsal interosseous
• plantar interosseous

Question 9

dorsal interossei:

origin and insertion

Answer 9

• origin:
  
  • adjacent sides of MT shafts 1-5,
  • peroneal sheath
• insertion:
  
  • MTPJ capsule, extensor expansion, and PP base
    
    • digit 2, both sides
    • digit 3&4, lateral sides

Question 10

dorsal interossei:

innervation and actions

Answer 10

inn:

• lateral plantar nerve (deep = 1-3, superficial = 4)
• 1st & 2nd: dually innervated by lateral plantar and deep fibular

actions:

• ABducts 2-4th digits
• simultaneous MTPJ plantarflexion & IP dorsiflexion of 2-4 digits

Question 11

plantar interossei;

origin and insertion

Answer 11

origin:

• medial surface of the shaft and plantar aspect of the base of MTs 3-5
• peroneal sheath

insertion:

• MTPJ capsule, extensor expansion, & medial side of PP base 3-5

Unipennate muscle bellies

Question 12

plantar interossei:

major actions, innervation

Answer 12

• actions:
  
  • ADDucts 3-5th digits
  • simultaneous MTPJ plantarflexion & IP dorsiflexion of digits 3-5
• innervation:
  
  • lateral plantar nerve (deep = 1-2, superficial = 3)

Question 13

Answer 13

Question 14

Answer 14

Question 15

Answer 15