Extrinsic Muscles of the Thoracic Limb

[Up] [extrinsicmm.] [intrinsicmm.] [arteries] [nerves] [Equine digit]

[image1] [image 2] [image 3] [image 4]

Can you identify the muscles that are labelled?

Muscle A is the brachiocephalic muscle. The asterisk is approximately at the level of the clavicular intersection, dividing the muscle into the cleidocervicalis (A1), cleidomastoideus (A2) and cleidobrachialis (A3) muscles. Just like the brachiocephalic muscle, whose name describes it's attachments (think about it), the name of muscle B, omotransversarius muscle, describes its attachments: omo comes from the Greek for shoulder, and transversarius refers to it's attachment on the transverse processes of the atlas. C1 and C2 are the cervical and thoracic portions, respectively, of the trapezius muscle. Muscle D is the latissimus dorsi muscle. "Traps" or "lats" are not acceptable identifications on a test for C and D. As you did with the pectoral muscles in Lab 4, use the locations of attachment and the direction of the muscle fibers to determine the actions of these muscles. Remember: extrinsic muscles have different functions depending on whether the limb is elevated or fixed (planted).