Rabbit Brachium
Text: Margaret Woods and Elizabeth Farrell. Photos: Margaret Woods
Lateral view of the rabbit brachium, anterior (cranial) to the bottom of the photo. In addition to the labelled muscles, the green pin is in supraspinatus, the blue pin in infraspinatus, and the latissimus dorsi is visible posterior to the triceps.
Medial vew of the rabbit brachium, anterior (cranial) to the bottom of the photo.
The locomotion of the rabbit is rather unique among quadrupedal mammals. The
type of hopping characteristic of this group is termed half-bounding. This type
of movement utilizes the forelimbs mainly as shock absorbers, with the hindlimbs
providing the majority of the propulsive force. As a result, the forelimbs are
much less robust and are proportionally smaller. In addition, pronation and
supination of the forelimbs is not possible, and the hands, which exhibit the
primitive mammalian characteristic of five digits, are not used for procuring
food.
| Muscle | Origin | Insertion | Action |
| Triceps | |||
|
Long head
|
ventral portion of the axillary border of the scapula | olecranon | extension of the elbow |
|
Lateral head
|
greater tubercle and the lateral portion of humerus | olecranon | extension of the elbow |
|
Medial head |
posterior surface of the humerus | olecranon | extension of the elbow |
|
Anconeus
|
medial aspect of the humerus | medial surface of olecranon | extension of the elbow |
| Brachialis | anterior and lateral surface of the humerus | medial surface of radius, medial border of ulna | flexion of elbow |
| Biceps brachii | anterior border of glenoid cavity containing the humerus | medial surface of radius and ulna | flexion of elbow |
| Coracobrachialis | coracoid process | distal, upper third the medial side of the humerus | flexion of elbow |
Begin this dissection by removing the skin and superficial fascia of the brachium. The dissection proceeded from the group of elbow extensors to elbow flexors. The long head and lateral head of the triceps were delineated first, and were relatively easy to identify and separate. The medial head of the triceps was significantly smaller than the long and lateral head, appearing on our specimen to be little more than a slip of muscle. The lateral head was the most robust. The medial head, being much smaller, was more difficult to find initially, but was also easily delineated once located. The insertion of anconeus is located inferior to the insertion of the medial head of the triceps. In this species, the biceps brachii has only one head. The biceps brachii was readily identifiable, and served as a good marker for the location of the brachialis muscle. The brachialis muscle had a very distinctive path, dividing into two distinct portions medially and laterally to head to the radius and ulna, respectively. It was a very thin muscle as well, and lay close to the bone. Because both of these muscles insert on the radius and ulna, it was not possible to follow their entire course without dissecting the muscles of the antebrachium as well.
Bensley, B.A. Practical Anatomy of the Rabbit. Toronto: The University Press, 1910.
Popesko, P., Rajtova, V., & Horak, J. A Colour Atlas of Anatomy of Small
Laboratory Animals. London: Wolfe Publishing Ltd, 1992.