A19 Flashcards
Digital extensors and flexors of the forelimb
Digital extensors of the forelimb
M. extensor digitalis communis
M. extensor digitlis lateralis
M. extensor digitorium 1 et 2
M. abductor digiti longus 1
Flexors of the forelimb
M. Flexor digitorum superficialis
M. flexor digitorum profundus
mm. interflexori
Superficial digital flexor
- Lies on the caudomedial side
- Covers the deep digital flexor
- Long belly, almost down to the carpus
- Runs in the carpal canal[1]
- Covered by the flexor retinaculum
- Lies in the common digital synovial sheath together with the deep digital flexor
- weaker and more superficial
O: medial epicondyle of the humerus
I: two limbs on the second phalanx, being per
A: flex the first two joint of the digits and activates several joints, fetlock extended = helps bearing weight
Carnivores
Pigs
Ruminents
Horse
Muscle bellies
1
2
2
1
Tendons of insertion
4
2
2
1
Tendinous
X
X
V
V
[1] The canal is made up by: Laterally: accessory carpal bone
Dorsally: palmar carpal ligament and carpal bones
Palmarly: flexor retinaculum
Deep digital flexor
- stronger and deep
- consist of the three heads in all the domestic mammals
- caput ulnare – originates on medial aspect of olecranon
- caput humerale – originates from the medial epicondyle, can be divided into three bellies
(not physically) - caput radiale - middle third of the radius
- the single tendon is held in position by the annular ligament of the carpus, connecting the accessory bone to the base of the medial metacarpal bone
- insert on all the digits corresponding to the interspecies difference
- glides over the sesamoid bones
- it flexes all the joints on the forefoot including the distal interphalangeal joints, fixes the fedtlock
M. extensor digitalis communis
- Lies laterally to the extensor carpi radialis
- M. extensor indicis – deep ulnar head, in horse it corresponds to the muscle of thiernesse
O: lateral epicondyle of humerus ( lateral ligament of elbow joint)
I: third phalanx of all the digits, except the first
A: extend the digits and also the carpal joint
Carnivores
Pigs
Ruminents
Horse
Muscle bellies
4
3
2
1
Tendons of insertion
4
4
2
1
Muscle of phillips
X
X
X
V
m. extensor indicis
X
V
V
V
M. extensor digitalis lateralis
- Lies between common extensor and extensor carpi ulnaris
O: lateral collateral ligament of elbow
I: interspecial differences, on the third phalanx if nothing else is indicated in the column
A: see column
Carnivores
Pigs
Ruminents
Horse
Muscle bellies
2
1
1
1
Tendons of insertion
3
3rd + 5th digits
2
4th + 5th digit
1
4th , attaches to 2nd phalanx
1
3rd digit prox phalanx
Two separate muscles
X
V
X
X
Action
3-5th digits
1st + 2nd joint
4th-5th digit
1st + 2nd joint
4th digit
1st joint
3rd digit
M. extensor pollicis longus et indicis
M. extensor pollicis longus et indicis
- Rudimentary in dogs
- Represented by m. extensor indicis in the other mammals
- Action: to extend 1st and 2nd digit in the dog, abduct dew claw
M. abductor pollicis longus
- Should belong to the carpal extensor but acts on the 1st digit in the carnivores
- Tendon passes obliquely over the extensor carpi radialis and ends at
- the base of the first metacarpal bone in carnivores
- base of mac2 in pigs
- base of mc2 in horses
- at mc3 in ruminants
Special short muscles
Only in carnivores
1st digit
2nd digit
5th digit
- m. flexor pollicis brevis
- m. abductor pollicis brevis
- m. adductor pollicis
- m. adductor digit II
- m. flexor digit V
- m. adductor digit V
- M. abductor digiti V
Mm. interflexori
- small and muscular or tendinous bundle
- binds the bellies or tendons of SDF and DDF
- Ø equine
There are also some short muscles of the digits, they are only well developed in animals with the need of activating individual digits, so the carnivores, in the other they are rudimentally or has become tendons of support fore the heavy weight bearing task. Divided into
Common short muscles:
- Mm. interossei
- Mm. lumbricales
- M. flexor brevis – originates from the SDF and inserts on the 5th digit in the dog and helps in the assisting of
flexing the 5th digit
Innervation of the different muscles
N. radialis
- M. extensor digitalis communis
- M. extensor digitalis lateralis
- M. extensor pollicis longus et indicis
- M. abductor pollicis longus
N. ulnaris
- M. flexor digitalis superficialis (Ø ca) -N.mediana
- M. flexor digitlais profundus
- caput ulnare
- caput humerale
N. medianus
- M. flexor digitalis profundus
- caput radiale
- mm. interflexori
