Text and photos: Catherine Lenox and Victoria Clayton
left shoulder of the ferret, cranial to the left, superficial dissection
left shoulder of the ferret, cranial to the left, deeper dissection
Before beginning the dissection, we made several observations concerning the superficial anatomy of the specimen. First, the specimen was identified as a female domestic ferret that had recently been pregnant or lactating. She had eight prominent teats. Although domestic ferrets typically have scent glands, none were present on this animal. It is common for captive ferrets to have their scent glands removed to prevent the secretion of a noxious odor when the animal is frightened or excited [1]. Her teeth were well worn with marked tartar and her tongue had noticeable papillae. Her black and tan coat was in good condition.
Ferrets are plantigrade animals, meaning when they walk their entire foot is in contact with the ground. They have 5 fully functional toes on each limb [1,3]. The clavicle is present in the ferret, however, it is reduced to a free-floating bone [1,2]. Primitive mammals use the clavicle to provide a strong connection between the scapula and sternum for support of the thoracic element. This is not the case in the mustelids. Their well-developed shoulder muscles provide support for the body between the forelimbs [2].
We began the dissection by skinning the upper arm, chest, and upper back. The initial cut was made along the midline of the dorsal side while holding the scalpel at a 45° angle to avoid damaging the underlying musculature. The medial cut was started at the cervical vertebrae and continued caudally to the end of the thoracic vertebrae. The specimen had little cutaneous adipose tissue. Next, cuts were made around the shoulder in order to remove the skin from the shoulder and upper arm area. Then, a ventral cut along the midline was made to reveal the pectoralis muscles.
The cutaneous trunci, a muscle superficial to the latissmus dorsi, is well developed in ferrets. It was cut while removing the skin on the lateral portion of the body. This muscle allows ferrets to twitch their skin and is not as well developed in some other mammals, such as humans.
The trapezius was the most superficial and dorsal muscle of the shoulder. It had three origins and was clearly divided into the clavotrapezius, acromiotrapezius, and spinotrapezius.
In quadrupeds, the pectoralis muscles are used as a ventral "sling" that support the weight of the body between the limbs. Additionally, they keep the limb under the body by adducting it [1,2]. The pectoralis superficialis was not well developed in the ferret. When reflected it revealed a larger pectoralis profundus. This is different from humans, who have a much larger pectoralis superficialis, called the pectoralis major.
The latissimus dorsi was a difficult muscle to dissect because it was very thin. It had a broad origin on the dorsal aspect of the ribcage. The insertion into the medial portion of the humerus was difficult to ascertain see because it was hard to reach. This muscle is important in fossorial animals because it pulls the humerus caudally [1]. Although the ferret lives in burrows created by other animals and does not dig itself [4], the wideness of the latissimus dorsi in the ferret may indicate that it has fossorial ancestors.
The deltoids were clearly divided into the spinodeltoid, acromiodeltoid, and clavodeltoid. All three of these muscles have the same function-pulling the humerus cranially-although the spinodeltoid also functions in abducting the humerus. All three deltoid muscles were of approximately equal size.
The supraspinatus, cranial to the scapular spine, was much larger than the infraspinatus. Both muscles are involved in humeral rotation, but the supraspinatus muscle also abducts the arm. The larger size of the supraspinatus muscle indicates that abduction may be an important part of the ferret's lifestyle, or may have been important in the lifestyle of its ancestors. For example, the ferret's fossorial ancestors may have used the supraspinatus muscle in digging. The teres major pulls the humerus caudally and was small in the ferret. The teres minor was incorporated in the infraspinatus muscle, though this is not the case in other quadrupeds such as the cat.
The trapezius was reflected to reveal the rhomboideus, which had four parts: rhomboideus capitis, rhomboideus cervicis, rhomboideus profundus, and rhomboideus thoracis [1]. The rhomboids, involved in pulling the scapula dorsally and medially, were also quite small.
The teres major, subscapularis, and serratus ventralis were difficult to identify because they were on the medial aspect of the humerus.
| Muscle | Origin | Insertion | Action (and references) |
| Cutaneous trunci | Over the lumbodorsal fascia | Antebrachial fascia of the axilla | Twitches or wrinkles skin over lateral body wall and flank [1,2]. |
| Clavotrapezius | Occiput and dorsal midline of neck | Clavicle and clavodeltoid | Pulls humerus cranially [1,2]. |
| Acromiotrapezius | Dorsal midline of neck | Acromion process | Pulls scapula dorsally [1,2]. |
| Spinotrapezius | Dorsal midline of thorax | Scapular spine | Rotates scapula caudally [1,2]. |
| Sternocleidomastoid | Sternum, clavicle | Occiput | Rotates head [2]. |
| Pectoralis superficialis | Sternum | Pectoral ridge and part of humerus distal to it | Pulls humerus cranially and adducts humerus [1,2]. |
| Pectoralis profundus | Sternum | Pectoral ridge of humerus | Adducts humerus [1,2]. |
| Latissimus dorsi | Dorsal fascia of thorax, some posterior ribs | Medial surface of humerus | Pulls humerus caudally [1,2]. |
| Levator scapulae ventralis | Transverse processes of atlas | Metacromion process of scapula | Pulls scapula cranially [2]. |
| Spinodeltoid | Scapular spine | Deltoid ridge of humerus | Pulls humerus cranially and abducts humerus [2]. |
| Acromiodeltoid | Acromion process | Deltoid ridge and tuberosity | Pulls humerus cranially [2]. |
| Clavodeltoid | Clavicle and clavotrapezius | Humerus distal to deltoid tuberosity | Pulls humerus cranially [2]. |
| Supraspinatus | Supraspinous fossa | Greater tubercle of humerus | Rotates and abducts arm [2]. |
| Infraspinatus (includes teres minor) | Infraspinous fossa | Greater tubercle of humerus | Rotates arm laterally [2]. |
| Teres major | Posteroventral border of scapula | Medial surface of humerus | Pulls humerus caudally [2]. |
| Rhomboideus | Dorsal midline of thorax and neck | Dorsal edge of scapula | Pulls scapula dorsally and medially [1,2]. |
| Subscapularis | Subscapular fossa | Lesser tubercle of humerus | Adducts arm [2]. |
| Serratus ventralis | Ribs | Dorsal border of scapula | Depresses scapula and supports trunk [2]. |
1. Fox, J.G. 1998. Biology and Diseases of the Ferret (2nd Ed.). Williams & Wilkins, Baltimore.
2. Klingener, D. 1980. Laboratory Anatomy of the Mink (2nd Ed.). William C. Brown, Dubuque, Iowa.
3. Anderson, E. 1989. The phylogeny of mustelids and the systematics of ferrets. Pp. 10-20 in Conservation Biology and the Black-Footed Ferret. U.S. Seal, ed. Yale University Press, New Haven.
4. Nowak, R.M. 1999. Walker's Mammals of the World (Vol. 1) (6th Ed.). Johns Hopkins University Press, Baltimore
Ferret Natural History
Ferret Brachium