A20 - Digital extensors and flexors of the hindlimb

Question 1

Which muscles should be mentioned in the topic?

Answer 1

Extensors of the hindlimb phalanges:

1. M. extensor digitalis longus
2. ​M. extensor digitalis lateralis
3. M. extensor digiti I. [hallucis] longus (ca)
4. ​M. extensor digitalis brevis

Flexors of the hindlimb phalanges:

1. M. flexor digitorum superficialis
2. M. flexor digitorum profundus
3. M. flexor digitorum brevis (ca)
4. M. interflexori (ca)
5. Mm. lumbricales (ca)
6. Mm. interossei

Question 2

Give the extensors of the hindlimb phalanges

Answer 2

1. M. extensor digitalis longus
2. ​M. extensor digitalis lateralis
3. M. extensor digiti I. [hallucis] longus (ca)
4. ​M. extensor digitalis brevis

Question 3

M. extensor digitalis longus

Answer 3

• Origin: Fossa extensoria of femur (together with peroneus tertius in eq?)
• Insertion: Processus extensorius of Ph 3:
  
  • Ca, sus: Digits 2 to 5
  • Eq: Digit 3
  • Ru: Digit 3 and 4
• Action:
  
  • Extends stifle
  • Flexes tarsus
  • Extends digits
• Innervation:
  
  • ​N. peroneus communis
    
    • R. profundus
    • R. superficialis

Question 4

M. extensor digitorum lateralis

Answer 4

• Origin: Fibula, proximal third
• ​Insertion:
  
  • Ca: Unites with long digital extensor’s tendon to reach digit 5, Ph3
  • Eq: Blends with the terminal tendon of the long extensor
• Action: Ca: Extend and abduct digit 5 (and flexes tarsus)
• Innervation:​
  
  • N. peroneus communis
    
    • R. profundus
    • R. superficialis

Question 5

M. extensor digiti I. [hallucis] longus

Answer 5

Ca

• Origin: Fibula, middle third
• Insertion: Radiates into fascia over metatarsophalangeal joint of digit 2
• Action:
  
  • Extend the digit 2 (and 1 if present)
  • Flexes tarsus
• Innervation:
  
  • ​N. peroneus communis
    
    • R. profundus
    • R. superficialis

Question 6

M. extensor digitalis brevis

Answer 6

• Origin: Tarsus, cranial surface
• Insertion: Ph1 of digit 2-5
• Action: Auxillary extensor of the digits 2-4
• Innervation:​
  
  • N. peroneus communis
    
    • R. profundus
    • R. superficialis

Question 7

Give the flexors of the hindlimb phalanges

Answer 7

1. M. flexor digitorum superficialis
2. M. flexor digitorum profundus
3. M. flexor digitorum brevis (ca)
4. M. interflexori (ca)
5. Mm. lumbricales (ca, eq)
6. Mm. interossei

Question 8

M. flexor digitalis superficialis

Answer 8

• Origin: Fossa supracondylaris of the femur (partly fused with m. gastrocenemius caput lateralis)
• Insertion: On the surface of tuber calcanei it makes the ​galea calcanea, ​then attaches to Ph2 of digits on plantar surface:
  
  • Ca: Digits 2-5
  • Eq: Digit 3(​tuberositas flexoria​)
  • Ru, Sus: Digits 3-4
• Action:
  
  • Flexes stifle
  • Extends hock
  • Flexes joints of corresponding digits
  • Eq: Part of the passive stay and fixation apparatus (femoropatellar loop)
• ​Innervation:
  
  • N. tibialis
    
    • R. cutaneous surae caudalis

Question 9

M. flexor digitorum profundus

Answer 9

• Consists of thee induvidual muscles:
  
  • M. flexor digitorum lateralis
  • M. flexor tibialis caudalis
  • M. flexor digitalis medialis
• Origin:
  
  • M. flexor digitorum lateralis:
    
    • ​Fibula, proximal caudal half
    • Tibia, proximal caudolateral border
    • Interosseous membrane
  • M. flexor digitorum medialis: Tibia, caudo-proximally
  • Eq: Only tibia
• Unites below tarsus
• Insertion:
  
  • Ca: Ph3 of digits 2-5, tuberculum flexorium (plantar)
  • Eq: fascies flexoria, undivided, digit 3
  • Ru, sus: Digits 3-4
• Action:
  
  • Extends tarsus
  • Flexes joints of corresponding digits of insertion
• Innervation:
  
  • ​N. tibialis
    
    • R. cutaneous surae caudalis

Question 10

M. flexor digitalis brevis

Answer 10

Ca

• Origin: The dorsal surface of the superficial digital flexor tendons
• Insertion: With the tendons of the deep digital flexor
• Action: Flexing the digits

Question 11

Mm. interflexorii

Answer 11

Ca, fe

• Origin: The tendon of the deep digital flexor with the suspensory ligament of the pad (where the deep flexor tendon splits into branches)
• Insertion: The tendons of the superficial digital flexor, more distally
• Action: Auxilary flexors of the digital joints

Question 12

Mm. lumbricales

Answer 12

Ca

• Origin: The abaxial borders of the tendons of the deep digital flexor
• Insertion: The proximal ends of the 1st phalanges of digits 3-5
• Action: To flex the first digital joint

Question 13

Mm. interossei

Answer 13

• Origin: Proximal part of the metatarsals
• Insertion: On the sesamoid bones of the first digital joint
• Action: To flex the metacarpalphalangeal joint of the supporting digits in ca and sus