Cat facial and masticatory muscles
Photo and text: Kyungmin Shin
This is a lateral view of the right side of the cat's face and head; superior is to the top of the photo.
A cat is a carnivore. Even a housecat hunts birds, mice and some other small animals. It uses some facial expression for communication, but not much more than other carnivores. A cat has whiskers and well-developed musculature for moving the whiskers or the vibrissae. Also, a cat can move its pinnae as it wishes, thus it has a well-developed musculature for moving the pinnae as well, although less so than the rabbit.
| Muscle | Origin | Insertion | Action |
| Platysma | Skin and its fascia near the middorsal line from the skull to the first thoracic vertebra | Skin and various structures around the eye and mouth | It moves skin of neck and face |
| Buccinator | Inferior to the nose and superior to the orbicularis oris muscle | It lies against the mucous membrane of the upper lip. | It raises the lip and helps to return food from the vestibule to the chewing surface of the teeth. |
| Orbicularis Oculi | Cranial corner of the eye and split into two to surround the eye | Caudal corner of the eye | It closes the eye. |
| Orbicularis Oris | Inferior to the nose and superior to the upper lip | Mandible | It closes the lip and is a pressor to the labial gland. |
| Temporalis | Zygomatic arch and the temporal fossa | To the outside of the coronoid process of the mandible | It elevates the mandible. |
| Masseter | Zygomatic and the zygomatic arch | Coronoid fossa of the mandible | It elevates the mandible. |
The challenging part of this lab is removing the skin from the face especially around the eye and mouth. Once the skin is removed, the platysma muscle is visible. It is a thin but wide sheath of muscle that seems to wrap around almost the entire face and neck area as it originates from the thoracic vertebra. Removing the platysma muscle requires caution, because it is easy to remove the orbicularis muscles with it. The orbicularis oculi muscle is easy to mistake as a part of the platysma muscle, because it is small muscle surrounding the eye, and also because the platysma muscle inserts into it. However, if the musculature around the eye is carefully looked at, one can see that the muscle fibers of the orbicularis oculi encircle the eye. The orbicularis oris muscle is also difficult to see as for the same reasons as the orbicularis oculi muscle. However, this muscle surrounds only the upper lip. Caudal and superior to this muscle is the buccinator muscle. This muscle is also a small strip of muscle that wraps around the upper lip superior to the orbicularis oris muscle. However, this is a deep muscle, only visible after cutting and reflecting the caninus muscle, which retracts the vibrissae and raises the upper lip. The caninus muscle is located near the vibrissae follicles and lies superficial and perpendicular to the buccinator muscle.
As in other carnivores, a cat has a large temporalis muscle and a smaller masseter
muscle like the ferret and the fox in contrast to the rabbit, which has a significant
masseter muscle and a small temporalis muscle. The temporalis muscle is the
largest and the strongest head muscle in a cat. There are supposed to be two
layers of the temporalis muscle, the smaller and the thinner superficial layer
and the massive deeper layer, which constitutes most of the temporalis muscle.
However, there are variations, and this cat did not have the divisions. The
temporalis muscle is covered by a tough fascia, which, at first glance looks
like a part of the skull. Compared to the temporalis muscle at the top of the
skull, the masseter muscle is at the side of the skull inferior to the temporalis
muscle. This muscle is smaller than the temporalis muscle, and it is tiny compared
to that of the rabbit. The cat, as a carnivore, uses its mouth for hunting and
biting, and therefore it has a large, well-developed temporalis muscle and less
developed masseter muscle. However, a cat does chew, so the masseter muscle
is not as small not underdeveloped as in some other carnivores that swallow
the food without chewing.
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