Rabbit antebrachium
Photo and text: Margaret Woods
superficial, lateral muscles of the rabbit antebrachium, anterior (craniad) to the bottom of the photo
Pre-lab:
O. cunniculus does not have a brachioradialis (supinator longus)
and cannot supinate its forearm or manus.
Extensor carpi ulnaris
Origin: Lateral epiconyle of the humerus and proximal, lateral surface of the
ulna
Insertion: base of the fifth metacarpal
Action: extends and adducts manus at the wrist joint
Extensor digitorum communis
Origin: lateral epicondyle of humerus and proximal end of ulna
Insertion: by four tendons on all phalanges of four lateral digits
Action: extends medial four digits and extends manus at wrist joint
Extensor digitorum lateralis (the following two muscles):
Extensor digiti quarti proprius
Origin: lateral epicondyle of humerus
Insertion: ungual phalanx of fourth digit
Action: extends fourth digit
Extensor digiti quinti proprius
Origin: lateral epicondyle of humerus
Insertion: head of the fifth metacarpal and base of first phalanx of this digit
Action: extends fifth digit
Extensor carpi radialis longus
Origin: lateral epicondyle of humerus
Insertion: base of second metacarpal
Action: extends and abducts manus at wrist joint
Extensor carpi radialis brevis
Origin: lateral epicondyle of humerus
Insertion: base of third metacarpal
Action: extends and abduct manus at wrist joint
Note: This muscle is partly fused with extensor carpi radialis brevis and their
tendons are closely associated on wrist
Abductor pollicis
Origin: anterolateral surface of radius and ulna
Insertion: base of first metacarpal
Action: abducts and extends first digit
Note: This muscle is partly covered by extensor digitorum communis.
Pronator teres
Origin: medial epicondyle of humerus
Insertion: ventral surface of radius
Action: pronates and flexes forearm
Flexor carpi radialis
Origin: medial epicondyle of humerus
Insertion: base of second metacarpal
Action: flexes and abducts manus
Palmaris
Origin: medial epicondyle of humerus
Insertion: superficially on volar fascia
Action: flexes manus
Note: This muscle is extremely slender and located between superficial portion
of flexor digitorum profundus and flexor carpi ulnaris)
Flexor digitorum profundus
Origin: (in four parts) (1)superficial portion - medial epicondyle of humerus,
(2) radial portion- ventral surface of radius, (3) middle portion- ventral of
ulna , and (4) ulnar portion - medial epicondyle of humerus in common with flexor
digitorum sublimus
Insertion: by five tendons on bases of the ungual phalanges
Action: flexes digit and manus
Flexor digitorum superficialis (flexor digitorum sublimis)
Origin: in common with the ulnar portion of flexor digitorum profundus from
the medial epicondyle of the humerus; proximal portion of ulna
Insertion: bases of the second phalanges of four lateral digits
Action: flexes four lateral digits and manus
Flexor carpi ulnaris
Origin: (two origins which lead to two short but separate heads of this muscle)
(1) medial epicondyle of humerus and (2) medial surface of olecranon
Insertion: pisiform bone
Action: flexes and adducts manus
After skinning the forearm and the manus, the dorsal carpal ligament was identified. This thickened ligament across the wrist had to be cut in order to follow the muscles and the tendons of the forearm to their insertions on the manus and the digits. After removing the loosely fitting superficial fascia the muscles of the antebrachium can be identified.
Starting with the lateral musculature- The superficial musculature includes (moving from most anterior to posterior) extensor carpi radialis, abductor pollicis, extensor digitorum lateralis, extensor digitorum ulnaris, and flexor carpi ulnaris. To reveal the deeper musculature on the lateral side of the antebrachium, one must make an incision through the most anterior muscle, extensor carpi radialis closer to its insertion tendon and reflect the muscle back. Directly dorsal to this cut muscle is extensor digitorum communis. To reveal other muscles, one must make an incision through the most posterior muscle, flexor carpi ulnaris. Once cut and reflected back, one can identify (from anterior to posterior) the two heads of flexor digitorum profundus and flexor digitorum superficialis (see figure).
Turning the rabbit over and identifying the medial musculature- The superficial musculature, from anterior to posterior, includes extensor carpi radialis, pronator teres, flexor carpi radialis, flexor digitorum profundus, and flexor carpi ulnaris.
O. cunniculus does not have a palmaris brevis, abductor pollis brevis, or an abductor digiti minimi. O. cunniculus has a rudimental first digit, which means it is extremely small and not very active. Therefore, the first digit does not have a lot of musculature affiliated with it. O. cunniculus has three lumbricals. O. cunniculus does not have a spring ligament.
Lumbricals
Origin: from the point of division of the tendon of the flexor digitorum profundus
Insertion: medial side of the first phalanx in each of the third, fourth, fifth
digits
Action: flexes, and extends digits at joints
Adductor digiti quinti, Adductor digiti quarti, Adductor digiti indicis
Origin: close together on the dorsal part of the tendon sheath of flexor digitorum
profundus
Insertion: by long thin tendons, respectively, to the radial sides of the fifth
and fourth digits and ulnar side of the second digit, just dorsal tothe interossei
Action: adducts digits
Note: Three slender muscles
Interossei
Origin: in pairs from the bases of the second and fifth metacarpals and related
in portions of the carpal bones
Insertion: sesamoid bones on the metacarpophalangeal joints
Action: adducts digits and assists lumbricals
Note: The fibers of each pair interlace so that the members cannot be smoothly
separated.
There was not an extensive amount of dissection done on the manus. Many of the tendons of the antebrachium musculature were followed to the palmar and dorsal surface of the manus to observe insertions. If one turns the manus to its palmar surface, the tendinous insertions of the antebrachium musculature can be seen. Directly dorsal to the superficial running tendons are the lumbricals. Without dissection but by using a probing instrument, one can probe underneath the lumbricals and see the interossei.
- Information about the origins and insertions of muscle was provided by Craigie.
- Information about the actions of the muscles was provdied by Agur & Lee.