Shoulder

Brachium

Antebrachium

Facial and Masticatory Muscles

Thorax and Heart

Brain

Body Wall

Hip and Thigh

Shank and Foot

Digestive System

Urinary and Reproductive Systems

Hip and Tail

Antebrachium of the Pig (Sus scrofa)

Text by Lazaro Gonzales, Jr.

Antebrachium:

Pigs are unguligrade artiodactyls [1].  This refers to a form of locomotion in which the mammal walks on its most distal phalanx (ungual phalanx).  Previous labs identify features of the shoulder and brachium that are important in this form of locomotion.  This lab focuses on the antebrachium and manus.  The fetal pig does not have pronator or supinator muscles that would enable it to rotate its limbs laterally or medially.  Little attention is given to the antebrachium in references for the musculature of the fetal pig.  This is mostly due to the emphasis on the fetal pig’s circulatory system and other internal anatomy.  The musculature of a fetal mammal is difficult to delineate and usually not fully formed.  Also, most musculature of the antebrachium serves in movement of the manus, which is limited in an unguligrade animal.  The extensors and flexors of the carpus (wrist) and digits are listed in the table below.  Unguligrades do not have digit 1, and the pollicis musculature is also lost.

General Dissection:

Remove the skin further from the carpus to the ungual.  Cut the skin along the antebrachium distally and reflect the skin from the entire forelimb.  Tough antebrachial fascia will cover the forelimb.  After examining the forelimb cut through this to reveal the musculature deep to it.  Separate the muscles out with a blunt probe, following the lines along the edges of the muscles. 

Comparative Anatomy:

The fetal pig has less developed musculature than the adult mammals from the other groups.  The musculature is softer and less striated.  As an unguligrade mammal it lacks digit 1 and the pollicis musculature.  Mammals that use other forms of locomotion have this structure and musculature.  The beaver has webbed hands, which are not found in the fetal pig, to help it with swimming.  The fetal pig most closely compares to the cat because of the similar form of locomotion.  Although the cat and pig are not closely related, they share cursorial characteristics.  Artiodactyls such as the pig or deer have short proximal limb segments, long distal limb segments, reduction of the foot, and development of unguals on those  phalanges that touch the ground.   

Muscles of the Antebrachium and Manus [1,2,3]:

References:

1. Odlaug, T.O.  1980.  Laboratory Anatomy of the Fetal Pig.  Wm. C. Brown Company Publishers, Dubuque, Iowa.

2. Walker, W.F.  1980.  Dissection of the Fetal Pig.  W.H. Freeman and Company, San Francisco, CA.

3. Smith, D.G.  1998.  A Dissection Guide and Atlas to the Fetal Pig.  Morton Publishing Company, Englewood, CO.