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

Facial and Masticatory muscles of the Cat (Felis catus)

Photos and text by Adam Hartstone-Rose

Introduction:

Cats are carnivores that use their teeth and jaws both to dispatch and disarticulate their prey.  Unlike herbivorous mammals, cats spend little time breaking down their food orally.  They consume large chunks of easily digestible meat.  Cats’ jaw muscles are adapted for force in the single dorsiventral plane.

Though cats use limited facial expression, they do have craniofacial musculature that enhances their senses.  Namely, they have specialized muscles that allow them to orient their pinnae in multiple directions for enhanced directional hearing.  They also have highly developed muscles that allow them to move their whiskers (vibrissae) for more acute tactile sensation.

Dissection Technique:

At this point there should already be a cut around the circumference of the neck that was the cranial border used during the removal of the skin of the thorax; if there is not one, then this is the place to begin.  From the free edge of the skin there, continue the blunt dissection technique of retracting the skin and breaking the loose connective tissue holding it to the underlying musculature.  Work from the caudal edge of the skin flap toward the nose on the dorsal surface of the head, and continue ventrally around the sides of the head, anterior to the pinnae.  Once the skin has been sufficiently separated make a midline sagittal cut, from the free edge of the skin to the nares to make its removal easier. The removal of the skin is difficult over many of the delicate facial muscles including the mystacial musculature superior to the mouth.  Much like the skin overlying the fleshy pads on the ventral surface of the manus, the skin over this region is so tightly associated with the underlying structures that it is nearly impossible to remove without damaging the muscles.  A sharp blade and steady hand are necessary to reveal the underlying hair follicles, though some damage is to be expected.

The frontalis muscle is fairly thin and adheres tightly to the skin.  Unless serious and, perhaps unwarranted, effort is expended, it will probably come off with the skin.  Other than that, the only musculature that is deeply invested in the skin of the dorsal side of the skull is the rostral-most part of the musculature that moves the pinnae.  These muscles run in a roughly parasagittal direction starting at the anterior edge of the base of the cartilaginous part of the ears.  It will have to be cut in order to remove the overlying skin.

Table 1.  Craniofacial musculature.  Adapted from [1].

Discussion:

As noted in the introduction, the musculature of the cat head is either part of the feeding apparatus or for moving the superficial sensory organs [2].  The masticatory muscles are powerful but relatively undifferentiated reflecting the cat’s inability to move the jaw in complex movements (as rodents do) in favor of allowing greater levels of leveraged force.  The cat chokes and tears, and does not chew.

The more differentiated muscles of the cat head, the muscles that move the ears and whiskers reflect the cat’s adaptation of keen senses for the location of prey.  The cat’s ability to hear in different directions and feel objects with its whiskers allows it to hunt efficiently when visibility is impaired, at night for example.

References:

1. Reighard, J. & Jennings H.S. 1935.  Anatomy of the Cat.  New York: Henry Holt and Co.

2. Tomo, S., Tomo, I., Nakajima, K., Townsend, G.C. & Hirata, K. 2002. Comparative anatomy of the buccinator muscle in cat (Felis domestica).  Anatomical Record. 267: 78-86