Muscles of the Face: Characteristics and Functions

The Muscles of the face they are so many and so varied that it can be very difficult to imagine how such a large number of muscle groups can be distributed in such a small space, that they also have such specific and differentiated functions.

The complexity of facial expression, in addition to the proper functions of phonation and swallowing, requires not only many muscle groups, but also extraordinary coordination between different muscle groups to achieve such a wide variety of movements, ranging from simple wink until you can whistle.

Muscles of the face

In general, the muscles of the face can be divided into two large groups: those of small size and with function limited to facial expression, and those of large size with a fundamental role in important functions such as speech, food and even the breathing.

A detailed analysis, muscle to muscle, of the more than 15 muscular structures that are found on the face goes far beyond the scope of this entry, to the point that it takes years of study of anatomy and surgical practices to know them in detail. In this opportunity all will be mentioned and only the most relevant ones will be described.

Index

  • 1 General characteristics
  • 2 Classification and functions
    • 2.1 Muscles of the auricular pavilions
    • 2.2 Muscles of the eyelids and eyebrows
    • 2.3 Muscles of the nose
    • 2.4 Muscles of the mouth and lips
  • 3 References

General characteristics

The vast majority are flat, thin muscles with a fairly discrete size / strength ratio; that is, they are not muscles that have many muscle fibers or that generate great power.

Almost all take two insertions in different points, one in the bones of the face and the other in the skin of the face or the aponeurosis of some neighboring muscle; Sometimes they can be both.

Larger muscles are the exception to this rule. It is the masseters, which have their two inserts on bone surfaces; they are able to move a joint and, per square centimeter of surface, they are among the most powerful muscles in the body.

Classification and functions

The muscles of the face can be classified according to their function and according to the anatomical area with which they are related.

According to its function, the muscles of the face can be divided into muscles of expression and muscles of chewing.

The muscles of the expression almost invariably take insertion in bone and skin, while those of the mastication always do it on bony surfaces.

On the other hand, according to its anatomical location the muscles of the face can be divided into:

- Muscles of the auricular pavilions.

- Muscles of the eyelids and eyebrows.

- Muscles of the nose.

- Muscles of the mouth and lips.

Muscles of the auricular pavilions

Due to the location of the auricular pavilions, their structure and the particular evolution of the human being, which no longer depends so much on the ear to survive, the muscles of the auricular pavilions are considered muscular vestiges.

Although they are present, their function is null. In fact, the cases of individuals with the ability to move their earlobes are exceptional.

In those cases in which it is possible to move them, it is due to the action of the anterior, posterior and superior atrial muscles, present in all people but in very few cases with enough force to have a visible effect.

Muscles of the eyelids and eyebrows

Its main function is to generate the movement of the eyebrows, to frown and, above all, to allow the eye opening; to this group belong:

- Occipito-frontal muscle

- Pyramidal muscle

- Superciliary muscle.

- Orbicular muscle of the eyelids.

The latter is the most important of all, since it allows eye closure; It is a large, flat, circular muscle that surrounds the outer part of the orbits. It is divided into several portions that allow you to close your eyes gently or"squeeze"your eyes as they close.

The opposite function (ocular opening) is due to the synergistic action of the levator palpebrae superior muscle, which"lifts"the eyelid like a blind as the orbicularis oculi relaxes, allowing the lower eyelid to fall almost by gravity.

It is important to remember that the levator del lid superior is not considered a muscle of the face, since it is born inside the orbit and ends in the upper eyelid; In addition, its innervation depends on the third cranial nerve (common ocular motor), unlike the muscles of the face, whose innervation is the responsibility of the VII cranial nerve (facial nerve).

Muscles of the nose

Of these muscles only one (pyramidal of the nose) has to do with the expression, while the rest has a specific function in the respiratory system.

- Pyramidal nose

- Transverse of the nose.

- Mirtiform.

- Dilator of the nose.

The mirtiform muscle is responsible for"depressing"the nasal ala and thus closing the entrance of the nasal passages, being this particularly useful when limiting the entrance of impurities as dust to the upper respiratory tract.

For its part, the transverse and the dilator of the nose act synergistically to do the opposite: dilate the entrance of the nostril to allow air to enter more easily.

In general, its action is not visible except in cases of severe respiratory distress, when its effect is so evident that it gives rise to a clinical sign known as nasal flaring, which consists of raising the wing of the nose with each inspiration .

Muscles of the mouth and lips

They are the most numerous and most widely distributed, occupying more than 60% of the total area of ​​the face.

These muscles are responsible for most facial expressions. In addition, some help in phonation, and some very special ones allow chewing: the masseters

- Buccinator.

- Orbicular of the lips.

- Common elevator of the nose and upper lip.

- Elevator of the upper lip.

- Canine muscle.

- Greater zygomatic.

- Lesser zygomaticus.

- Risorio.

- Triangular of the lips.

- Square of the chin.

- Tassel of the chin.

- Masetero.

All these muscles, innervated almost entirely by the facial nerve, are responsible for the hundreds of facial expressions of the human face.

For example, the smile is a consequence of the contraction of risorio and the zygomatic major and minor muscles; likewise, the slight contraction of this pair of muscles allows to elevate the labial conmisura.

On the other hand, the buccinator retracts the labial commissures; This allows you to whistle, play wind instruments and dislodge the food that accumulates in the vestibular area of ​​the gums.

The orbicularis of the lips is another specialized muscle that allows to close the mouth, besides helping in the complex of movements necessary to suck.

Finally there is the masseter which, together with the pterygoid muscles (belonging to the pterygoid fossa), forms part of the chewing muscles.

It is capable of exerting a pressure of 90 kg / cm2, which makes it one of the strongest muscles in the body considering the size / force relationship exercised.

It takes insertion in the zygomatic arch and in the ascending branch of the lower jaw, allowing the buccal closure and chewing. For this they work in synergy with the rest of the chewing muscles and in coordination with the muscles of the neck, responsible for the buccal opening (digastric, mylohyoid, infrahyoid muscles, among others).

References

  1. Pessa, J.E., Zadoo, V.P., Adrian, J.E., Yuan, C.H., Aydelotte, J., & Garza, J.R. (1998). Variability of the midfacial muscles: analysis of 50 hemifacial cadaver dissections. Plastic and reconstructive surgery , 102 (6), 1888-1893.
  2. Gasser, R. F. (1967). The development of the facial muscles in man. Developmental Dynamics , 120 (2), 357-375.
  3. Goodmurphy, C. W., & Ovalle, W. K. (1999). Morphological study of two human facial muscles: orbicularis oculi and corrugator supercilii. Clinical Anatomy , 12 (1), 1-11.
  4. Szentágothai, J. (1948). The representation of facial and scalp muscles in the facial nucleus. Journal of Comparative Neurology , 88 (2), 207-220.
  5. Freilinger, G., Gruber, H., Happak, W., & Pechmann, U. (1987). Surgical anatomy of the mimic muscle system and the facial nerve: importance for reconstructive and aesthetic surgery. Plastic and reconstructive surgery , 80 (5), 686-690.
  6. Rubin, L. R., Mishriki, Y., & Lee, G. (1989). Anatomy of the nasolabial fold: the keystone of the smiling mechanism. Plastic and reconstructive surgery , 83 (1), 1-10.
  7. Schwarting, S., Schröder, M., Stennert, E., & Goebel, H. H. (1984). Morphology of denervated human facial muscles. Orl , 46 (5), 248-256.


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