HEAD MUSCLES AND THEIR CHARACTERISTICS (WITH PICTURES) - ANATOMY AND PHYSIOLOGY - 2025

The muscles of the head are all those muscle groups that cover the bony structures of the skull. They can be divided from the topographical point of view into two large groups, the muscles of the head proper and the facial muscles.

Of these two groups, the head or cranial muscles are usually the largest and most powerful, being responsible for very specific functions such as chewing.

Source: Marcelo A Di Cicco

For their part, the muscles of the face are smaller. Its fibers in many cases lack bony insertions, and their main function is to take part in facial expression. For this reason, they are also often called the "muscles of mimicry."

The muscles of the face can be subdivided according to the area of ​​expression on which they influence. Thus, they are subdivided into muscles of the orbit, mouth, nose and ears.

General classification of the muscles of the head

Lateral anatomy of the head

Roughly, the muscles of the head are subdivided into two large groups:

- Head or cranial muscles.

- Facial muscles.

The muscles of the head are the largest and most powerful. They are subdivided into two large groups, the covering muscles and the chewing muscles.

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On the other hand, the muscles of the face are small and are characterized because part of their attachments are in the skin and aponeurosis, instead of being all in the bone as is usually the case with most striated muscles.

This characteristic of their insertions is what allows them to modify facial expression, since their contraction "drags" the overlying skin with it.

Head or cranial muscles

Patrick J. Lynch, medical illustrator

They are the large and voluminous muscles that are responsible for covering the skull and providing motility to the jaw during chewing.

Coating muscles

Within this group there is only one muscle included, known as the occipital-frontal muscle. This broad, flat, and relatively long muscle covers the entire cranial vault and emits very thin bundles that insert into the skin overlying the forehead.

The occipital-frontal muscle is also known as the epicranial muscle, and it consists of both muscular and tendinous portions.

The tendinous portions are located mainly in the posterior insertion, continuing with the aponeurosis of the posterior region of the neck and in the highest part of the cranial vault. There it serves as an interface to the anterior and posterior bellies of the muscle.

For its part, the muscular portion is made up of the occipital belly and the frontal belly. The occipital belly takes insertion in the posterior border of the occipital bone, extending between both mastoid processes.

On the other hand, the anterior belly takes its most distal insertions on the skin of the forehead, just above the eyebrows.

When the posterior belly contracts, the eyebrows are raised and the scalp is moved discreetly backwards; whereas when the anterior belly is contracted, the brow is frowned.

Chewing muscles

The chewing muscles are four muscles that are located on each side of the jaw. They are as follows:

- Masseter muscle.

- Temporal muscle.

- External pterygoid.

- Internal pterygoid.

Per square centimeter of surface area they are the most powerful muscles in the human body, especially the masseter. By working in unison, they allow for the chewing movement.

Masseter muscle

It is a thick, quadrilateral muscle that attaches to the lower border of the zygomatic arch. From there it extends to the lateral aspect of the ascending ramus of the maxilla.

Temporal muscle

It occupies the entire temporal fossa. It is fan-shaped, so all its fibers converge in a very thick tendon that takes insertion in the coronoid process of the mandible, as well as in its medial aspect and anterior border.

External (or lateral) pterygoid muscle

Its attachments are on the underside of the greater wing of the sphenoid and the pterygoid process. From there, its fibers are directed almost horizontally towards the condyle of the mandible, where they are inserted, practically on the capsule of the temporomandibular joint.

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It arises from the pterygoid process. From there, its fibers are directed downward and outward to reach the angle of the mandible, where they take their distal insertion.

The joint action of all these muscles allows the chewing process. When the mouth is open, the simultaneous contraction of the masseter, temporal and internal pterygoid closes the mouth.

On the other hand, the simultaneous contraction of both external pterygoids moves the mandible forward; while the unilateral contraction of each of the external pterygoids allows lateral movement of the mandible.

Muscles of the face

They are all those muscles that cover the face and whose insertions take place both in the bones of the face and in the skin that covers them.

Their common characteristic is that when they contract, they drag the overlying skin with them, since they lack aponeurosis. Therefore, the contraction of each particular muscle is responsible for a gesture. Thus, collectively, all these muscles are known as "mimic muscles."

In order to facilitate their understanding and topographic organization, they can be divided according to the anatomical area with which they are most closely related. However, in practice their fibers can overlap at certain points.

According to the anatomical area of ​​the face they occupy, the muscles of mimicry and expression can be divided into:

- Muscles of the eyelids and eyebrows.

- Muscles of the nose.

- Muscles of the lips and mouth.

- Muscles of the ears.

- Muscles of the chin.

Each of them is responsible for a particular gesture, to such an extent that some of them receive their name from the gesture they produce. This is what happens, for example, with the risorio muscle (responsible for the mimicry associated with laughter).

Muscles of the eyelids and eyebrows

They are all those muscles that surround the eye sockets and provide movement to the skin of the eyebrows and eyelids. The elevators of the upper eyelid are not included in this group, since they are intraorbital and their innervation does not depend on the facial nerve.

Pyramidal muscle

It is a small muscle located on the back of the nose, between both eyebrows. When contracted, the brow furrows, and the inner ends of the eyebrows are directed downward.

Orbicularis of the eyelids

Its fibers run in pairs, forming an oval around the orbit. When contracting, they close the eyelids. When the contraction is very powerful, they compress the lacrimal sacs.

In addition to closing the eyes, they cause a certain downward movement to the eyebrows.

Superciliary muscle

In even number, it attaches to the frontal muscle and to the skin where the eyebrows meet. It is an antagonist of the pyramidal muscle, which is why when contracting it raises the eyebrows and brings them discreetly outwards.

When the contraction is vigorous, it manages to contract the skin of the forehead, working synergistically with the anterior belly of the occiput-frontal.

Muscles of the nose

They are several muscles that cover the nasal pyramid and the adjacent areas. Most have a function in expression, although they can play a functional role (although limited).

Transverse muscle of the nose

An odd and triangular muscle that covers practically the entire nasal pyramid. Its distal attachments are located in the sulcus of the wing of the nose. By contracting this muscle, it closes the nostrils by depressing the wing of the nose.

Mirtiform muscle

Another odd muscle that sits just below the nasal septum, where it actually inserts proximally. Its distal insertion is in the myrtiform fossa of the maxilla.

When contracting, it acts synergistically with the transverse part of the nose, closing the nostrils, since it attracts both the nasal septum and the wings of the nose down and back.

Nose Wing Elevator

In even number, these muscles antagonize the action of the transverse-myrtiform joint; that is, they open the wings of the nose.

Its insertion is located in the upper jaw, immediately outside the most distal insertion of the transverse. From there, its fibers are directed towards the upper part of the wing of the nose, where they take insertion.

Muscles of the lips and mouth

They are the largest and most complex group, since in addition to participating in mimicry they also play a role in phonation.

Superficial levator muscle of the nose and upper lip

It is a long, thin, even muscle that takes insertion at the medial angle of the orbit, from where its fibers run downward and outward. In its journey it emits some muscle fascicles that are inserted in the lateral part of the wing of the nose, continuing its journey to end in the most superior and external area of ​​the upper lip.

When contracting, it elevates both the wing of the nose and the corner of the mouth.

Elevator of the upper lip

Also in even number, the levator palpebrae is a thin muscle that is located outside and behind the preceding one (superficial levator ala of the nose and upper lip).

Its proximal insertion is the lower edge of the orbit, while the distal one is the upper lip, which rises when contracted.

Canine muscle

Also known as the levator angle of the mouth, this small muscle inserts into the canine fossa of the upper jaw, extending to the skin of the labial commissure.

By contracting it raises the angle of the mouth.

Buccinator muscle

It is a paired muscle located between the orbicularis oculi in front and the masseter behind. Its distal attachments are found on the alveolar border of both the upper and lower jaws, while its distal attachments are in the thickness of the buccal mucosa.

When contracted, the transverse diameter of the mouth widens. It is considered an essential muscle to be able to whistle, since when contracted it allows to expel pressurized air through the mouth.

Zygomaticus major and minor muscles

It is a pair of parallel, tapered muscles (two on each side of the face), which run from the cheekbone to the corner of the mouth.

The minor zygomaticus muscle goes inside and the major one outside, this being a little more prominent than the first. As the zygomatic muscles contract, the corner of the mouth rises.

Triangular lip muscle

Also known as the angle depressor of the mouth, in even numbers this muscle takes proximal insertion in the integuments adjacent to the labial commissures, while the distal is in the lower jaw.

Its effect is antagonistic to that of zygomatics, so when contracting the lip corner is depressed.

Laughter muscle

These are two triangular muscles (one on each side of the face) whose distal attachments are found in the thickness of the subcutaneous cellular tissue of the parotid region. From there, its fibers converge in a fan shape to terminate at the proximal insertion located at the corner of the lips.

Due to its almost horizontal arrangement, when both risoria muscles contract in unison, the transverse diameter of the mouth increases, and the commissures rise discreetly. This causes the typical gesture of a smile, which has earned the name of this muscle.

Orbicularis of the lips

It is the largest and most powerful muscle in the mouth. Elliptical in shape, it is an odd muscle that surrounds the mouth opening. Its contraction purses the lips, and depending on the fascicles that are contracted, it projects them forward or backward.

Ear muscles

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They are atrophied muscle remnants in more than 80% of people. In fact, there are few individuals who still retain movement of the pinna. However, although atrophied, it is still possible to identify three muscles in the pinna:

- Anterior auricular muscle.

- Posterior auricular muscle.

- Superior auricular muscle.

They are considered vestiges of functional muscles that once had the responsibility of opening the external auditory canal and orienting the pinna, functions that no longer exist in the modern human.

Chin muscles

They are muscles that take insertion into the bony structures of the chin and the skin adjacent to the lips.

Square chin muscle

It is a small, odd muscle located below the lower lip, inside the triangular muscles of the lips. Takes insertion into the lower jaw (distal) and the thickness of the lower lip (proximal). Its contraction generates depression of the lower lip.

Mental muscle

It is a very small and conical paired muscle that takes its proximal insertion in the lower jaw, just below the gums, and its distal insertion in the skin of the chin. The contraction of the mental muscle elevates the skin of the chin as well as the upper lip.

References

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