Head muscles

Head muscles . They help the skin of the face and skull to move ; to the opening and occlusion of the facial orifices, to the movement of the bones involved in chewing, and to mimic expression.

Summary

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  • 1 Classification
  • 2 Chewing muscles
    • 1 Masseter muscle
    • 2 Temporal muscle
    • 3 Lateral pterygoid muscle
    • 4 Medial pterygoid muscle
    • 5 Functions
  • 3 Mimic muscles
    • 1 Evolution of facial musculature
  • 4 Calvaria muscles
    • 1 Head muscles
    • 2 Functions
  • 5 extraordinary muscles
    • 1 Cancer muscle
    • 2 Orbicularis oculi muscle
    • 3 Muscles of the oral cleft seen from the inside
  • 6 Perioral muscles
    • 1 Minor zygomatic
    • 2 Greater zygomatic
    • 3 risorio muscle
    • 4 Mouth angle depressant
    • 5 Mouth Angle Elevator
    • 6 Lower lip depressor
    • 7 Mental muscle
    • 8 Buccinator
    • 9 Orbicular of the mouth
  • 7 Perinasal muscles
    • 1 Nasal muscle
  • 8 Fascia of the head
  • 9 Sources

Classification

Excluding the striated muscles belonging to the sense organs ( sight and hearing ) and to the upper part of the digestive system , the other muscles of the head can be classified into the following groups:

  • Mastication muscles: derived from the first visceral (mandibular) arch, innervated by n. trigeminal.
  • Mimic muscles: derived from the second visceral arch (hyoid), innervated by n. facial.
  • Pterygoid muscles(Fig. 1)

Fig. 1. Pterygoid muscles .

  1. Zygomatic bone(serrated), maxilla
  2. Greater zygomaticus muscles
  3. Buccinator muscles
  4. MouthAngle Depressant
  5. Parotid duct
  6. Pterygomandibular raphe
  7. mandibular style
  8. Medial pterygoid muscles
  9. Styloid process
  10. External acoustic meatus
  11. Articular disc
  12. Condylar process (serrated)
  13. Lateral pterygoid muscles

Fig. 2. Anterior part of the skull with the mandible and the chewing muscles ; internal view.

Anterior part of the skull with the jaw and the chewing muscles; internal view. (Fig. 2)

  1. Medial pterygoid muscle
  2. Lateral pterygoid muscle
  3. Masseter muscle
  4. Mylohyoid muscle (start)
  5. Genioglossus muscle onset
  6. Genihyoid muscle start

Chewing muscles

The four muscles of chewing, on each side, are genetically related to each other (origin of the same visceral arch, the mandibular), morphologically (all are inserted into the jaw , to which they move), and functionally (they carry out the movements chews of the jaw, which determines its location).

Masseter muscle

The masseter muscle is thick, quadrilateral in shape. It begins at the lower edge of the zygomatic bone and in the arch of the same name, and is inserted into the maseteric tuberosity and on the external face of the mandibular branch.

Temporal muscle

Due to its wide initiation, the temporalis muscle occupies the entire space of the temporal fossa of the skull , reaching the temporal line from above. The muscular fascicles, arranged in a fan shape , converge in a consistent tendon that passes behind the zygomatic arch and is going to insert into the coronoid process of the jaw .

Lateral pterygoid muscle

The pterygoideus lateralis muscle begins on the underside of the greater wing of the sphenoid and in the pterygoid process. The muscle is directed almost horizontally backward and laterally and inserts into the neck of the mandibular condyle , as well as into the capsule and articular disc of the temporomandibular joint (Figures 1 and 2).

Medial pterygoid muscle

The pterygoideus medíalis muscle begins in the pterygoid fossa of the pterygoid process. It is directed down and laterally, and is to be inserted on the inner side of the angle of the mandible , symmetrically with the masseter muscles , in the homonymous tuberosity.

Features

The masseter, temporal and medial pterygoid muscles , when the mouth is open, attract the jaw towards the maxilla or, in other words, close the mouth. In the joint contraction of the two lateral pterygoid muscles, the advance of the mandible takes place.

The opposite movement is made by the posterior fibers of the temporal muscles, which are directed almost horizontally from back to front. When the lateral pterygoid muscle contracts exclusively on one side, the jaw moves from the opposite side to the contracting muscle.

The temporal muscles are also related to articulated language, giving the jaw a certain position during the process.

Mimic muscles

The visceral musculature of the head , originally related to the viscera of the head and neck , was gradually transformed in part into the cutaneous musculature of the neck, from which, by way of differentiation into thin independent fascicles, the musculature was formed. mimicking the face. This explains the intimate connection between the mimic muscles and the skin they set in motion. This also explains the other peculiarities of the structure and function of these muscles.

Thus, unlike skeletal muscles, mimic muscles do not have bilateral insertion in the bones , and are necessarily attached to the skin or mucosa at one or both ends. Because of this they lack fascia and by contracting they set the skin in motion . When relaxing, the skin recovers its previous position by virtue of its elasticity, which is why the role of the antagonistic muscles is, in this case, considerably less than that of the skeletal muscles.

The mimic muscles appear as small and thin muscle fascicles, grouped around the natural holes: mouth , nose , orbits and ears , participating in one way or another in closing or, conversely, opening these holes.

The closing muscles (sphincters) are currently located around the annular hole and the dilators are in the radial direction. By varying the shape of the holes and moving the skin with the formation of different folds, the mimic muscles give the face a certain expression, corresponding to this or that state of mind.

Those variations in the expression of the face are called mimicry, from which the name of the muscles is derived. Apart from its main function, the expression of sensations, the mimic muscles also participate in language , chewing, etc.

Fig. 3 Evolution of the facial musculature.

Evolution of the facial musculature

The facial musculature evolved as shown (Fig. 3):

  • Primitive reptile
  • Contemporary reptile (gatteria Sphenodon punctatus)
  • Primitive mammal(echidna)
  • Gorilla
  • Man

The shortening of the mandibular apparatus and the participation of the lips in articulated language lead to the particular development of the mimic muscles around the mouth , and on the contrary, the musculature of the ears , so well developed in animals, in man is it was reducing, remaining only in the form of rudimentary muscles.

Calvaria muscles

Almost the entire calvaria ( skull vault ) (Fig. 4) is covered by the thin epicranial or occipitofrontal muscle ( epicranius muscles), which has an extensive tendon part, the epicranial aponeurosis or aponeurotic galea, and a muscular part subdivided into three parts or independent bellies:

  • Anterior belly, frontal muscle or frontal belly, begins in the skinof the eyebrows and continues with the anterior part of the fascia.
  • Posterior belly, occipital muscle or occipital belly, starts at the superior nuchal line and continues at the posterior part of the fascia.
  • Ventre lateralis subdivided into three small muscles that are directed to the pinna of the ear; ahead, the anterior auricular muscle; above, the upper earpiece, and behind, the posterior earpiece. The three atrial muscles are continued with the lateral part of the epicranial fascia. The aponeurotic galea covers the middle part of the calvaria, constituting the central part of the epicranial muscle.

Head muscles

Fig. 4. Muscles of the head .

The muscles of the head include (Fig. 4.):

  1. Gale Aponeurotica
  2. Temporal fascia (superficial lamina)
  3. Temporal fascia (deep lamina)
  4. Temporal muscle
  5. Front belly
  6. Orbicularis oculi muscle
  7. Superciliary corrugator muscle
  8. Cancer muscle
  9. Medial palpebral ligament
  10. Minor zygomatic muscle
  11. Elevator muscle of upper lip and nose wing
  12. Elevator muscle of the upper lip
  13. Nasal muscle (transverse portion)
  14. Nasal muscle (wing portion)
  15. Depressor muscle of the nasal septum
  16. Elevator muscle of the angle of the mouth
  17. Orbicularis muscle of the mouth
  18. Depressor muscle of the corner of the mouth (sectioned)
  19. Mental muscle
  20. Depressor muscle of lower lip
  21. Submandibular gland
  22. Sternocleidomastoid muscle
  23. Trapezius muscle
  24. Masseter muscle
  25. Buccinator muscle
  26. Parotid gland
  27. Parotid duct
  28. Adipose body of the mouth
  29. Greater zygomatic muscle
  30. Occipital belly

Features

Having a loose bond with the periosteum of the skull bones , the epicranial fascia is, on the contrary, very well attached to the scalp, so it can slide together with it, as a result of contraction of the frontal or occipital muscle .

When the epicranial fascia is fixed by the occipital belly, the frontal belly raises the eyebrows in an arch and forms transverse folds in the forehead. The auricular muscles (lateral belly of the epicranial muscles) in most people are developed so weakly that their action is almost nil. The vestiges of it in man are a classic example of rudimentary organs . As is known, people able to move their ears are observed with very little frequency.

According to another wording of the PNA, the auricular muscles constitute an independent group of muscles located around the ear; the other two bellies of the epicranial muscles, frontal and occipital, constitute the occipitofrontal muscle.

Extraordinary muscles

Cancer muscle

The procerus muscle is the muscle of the proud. It begins in the bony dorsum of the nose and in the fascia of the nasal muscle and will end in the skin of the glabella region, continuing in the frontal muscle. It is a depressant of the skin of the mentioned region and causes the formation of transverse folds in the eyebrows.

Orbicularis oculi muscle

The orbicularis oculi muscle outlines the aditum of the orbit, being arranged on its wide peripheral part on the bony edge of the orbit, the orbital portion, and on its central part, the palpebral portion, on the eyelids . A third, small part, the lacrimal portion is still distinguished. The latter is part of the palpebral portion, originating from the walls of the lacrimal sac, which, when dilated, influences the aspiration of tears through the lacrimal canaliculi.

The palpebral portion occludes the eyelids. The orbital portion due to its intense contraction makes the eyes squint . The upper fibers of this portion, due to their isolated contraction, cause the brow skin to drop together with the eyebrows , giving the brows a rectilinear disposition, erasing the transverse folds of the [forehead]. In this sense, it is an antagonist of the frontal belly of the epicranial muscle.
In the orbicularis oculi muscle there is still a small portion, located below the orbital portion, the corrugator muscle of the eyebrows (superciliary) ( corrugator supercilii muscles ).

This portion of the eye socket brings the eyebrows closer together and causes the formation of vertical folds or wrinkles between the eyebrows, a space located above the root of the nose . Frequently, in addition to these vertical folds, short horizontal wrinkles are formed on the eyebrow, located in the middle third of the forehead and conditioned by the joint action with the frontal muscle. This position of the eyebrows is observed in states of suffering, pain, being very characteristic in the expression of serious emotional feelings.

Fig. 5 Muscles of the oral cleft.

Muscles of the oral cleft seen from the inside

Looking at the muscles of the oral cleft from the inside, you get the following:

  • 1, 6 nasal muscles
  • 2, 3 orbicularis muscles of the mouth
  • 4 buccinator muscles
  • 5 lip depressor muscles

Perioral muscles

Upper lip elevator ( levator labii superioris muscles ). It begins in the form of a quadrangular lamella at the infraorbital edge of the maxilla, and converging its fascicles, it continues mostly in the skin of the nasolabial fold (Figures 4 and 5).

A fascicle that goes to the wing of the nose is detached from this muscle, which is why it received the independent name of the levator labii superioris and the nose wing muscles ( levator labii superioris alaeque nasi muscles ). By contracting this muscle , the upper lip rises, deepening the nasolabial sulcus ( suclus nasolabialis ) and pulling the wing of the nose upward, widens the nostrils (nares).

Minor zygomatic

The zygomaticus minor muscle begins in the zygomatic bone and attaches to the nasolabial fold, deepening it with its contraction.

Greater zygomatic

The zygomaticus major muscle ). It extends from the lateral aspect of the zygomatic bone to the lip commissure and in part to the upper lip. It pulls the angle of the mouth up and laterally, causing the nasolabial fold to intensify. With the contraction of these muscles, the face becomes smiling and therefore the zygomaticus major muscle is preferably a laughing muscle.

Risorio muscle

The risorius muscle is made up of a small transverse bundle. It begins in the parotid and masonic fascia and is directed towards the angle of the mouth ; often this muscle does not exist. Extend your mouth during laughter ; in some people, as a result of the insertion of this muscle into the skin of the cheeks , a small fossa forms on the side of the lip during its contraction.

Mouth Angle Depressant

The depressor anguli oris muscles constitute a triangular muscular lamina that begins at its base at the lower edge of the mandible , lateral to the mental tubercle. Due to its vertex, it is inserted into the skin , near the corner of the mouth and upper lip. It is a depressor of the angle of the mouth and converts the nasolabial fold into a rectilinear one. The descent of the corners of the mouth gives the face an expression of sadness .

Mouth angle elevator

The levator anguli oris muscles are quadrilateral, located below the elevator of the upper lip and the greater zygomaticus, it begins in the canine fossa of the maxilla (that is why it was previously called canine muscle), below the infraorbital hole and is going to insert into the lip commissure. It is an elevator and adductor of the lip commissure.

Lower lip depressor

The depressor labü inferioris muscle is located directly on the bone . It begins at the edge of the jaw , constituting a prolongation of the platysma, and going obliquely it will insert into all the skin of the lower lip, reaching the free edge of it. Pull the lower lip down and somewhat laterally, as seen, for example, in the mime gesture of disgust.

Mental muscle

The mentalis muscle is one of the most powerful mimic muscles. Part of the alveolar eminence of the lower incisors and canines and will be inserted into the skin of the chin . It raises the skin of the chin forming small pits as well as the lower lip, compressing it against the upper one.

Buccinator

The buccinator muscle appears as a large quadrilateral muscle layer, which forms the lateral wall of the oral cavity, being in direct contact with the mucosa of the mouth .

It begins in the alveolar process of the maxilla at the level of the first molar and continues backwards, up to the pterygoid process, then descends along the pterygomandibular raphe ( raphe pterygomandibularis ) (fibrous ligament extended between the pterygoid hook and the buccinator crest of the mandible ) and continues along the buccinate crest and the lateral wall of the alveoli of the molars, going forward, up to the corner of the lips. At the level of the second upper molar, the muscle is crossed by the parotid duct (ductus parotideus).

The external face of the buccinator muscle is covered by the oropharyngeal fascia, to which the fatty body of the cheek (Bichat) is applied . The action of the muscle consists essentially in expelling the contents of the buccal vestibule to the outside, for example, the air when playing a wind instrument , from where the name of those muscles comes (buccinator muscles, trumpet muscle).

Orbicular of the mouth

The orbicularis oris muscle is located in the thickness of the lips , forming a circle or crown around the oral cleft. The muscle fibers, in both the upper and lower lip, run from the lip corners to the midline, where they interlock with the homologous fibers on the opposite side.

A multitude of fascicles of neighboring muscles are associated with the muscle. As the peripheral portion of the orbicularis muscle contracts, the lips thicken moving forward, as in the kiss ; If the portion below the red lip edge contracts , the lips come into intimate contact, folding inward, causing the red lip to disappear.

The mouth orbicular , located around the mouth, serves as a sphincter, that is, a muscle that closes the oral cleft. In this sense, it is an antagonist of the radial muscles of the mouth, that is, of the muscles that start from the orbicular region as divergent rays and that act by opening the mouth (levator muscles of the upper lip and of the buccal angle, lip pressors lower and buccal angle, etc.).

Perinasal muscles

Nasal muscle

The nasalis muscle is weakly developed, partially covered by the elevators of the upper lip. It begins in the maxilla, in the alveolar eminences of the upper lateral incisors, immediately subdividing into three parts: transverse portion ( pars transversa ), alar portion ( pars alaris ) and depressor muscle of the nasal septum (depressor septi nasi muscle ).

The most lateral portion, the transverse portion, rises towards the dorsum of the nose in its cartilaginous portion, continuing in a tendinous lamella that joins the homonymous lamella on the opposite side; By contracting it depresses the cartilaginous part of the nose. The wing portion, muscle of the wing of the nose, constitutes a short portion that goes to the nasal wing, causing it to descend as it contracts, which is why it is called the depressor muscle of the nasal septum.

Head fascia

The epicranial fascia (Fig. 4) covers the calvaria, in its lateral parts it thins considerably until it forms a loose fibrous lamella, below which the dense, shiny temporal fascia extends, covering the homonymous muscle , beginning with up the timeline. Below, this fascia is inserted into the zygomatic arch unfolding into two sheets of which the superficial one adheres to the external face of the arch, and the deep one to its internal face. A space filled with fatty tissue is delimited between both sheets.

The temporal fascia converts the temporal fossa into an osteofibrous receptacle that contains the temporal muscle and a certain amount of adipose tissue. The masseter muscle is covered by the maseteric fascia ( masseteric fascia ), which wraps around the muscle and inserts above the zygomatic arch, below the edge of the jaw, and behind and in front of the branch. Backwards and, in part, on its anterior face, it is related to the parotid fascia (parotid fascia ), which forms the capsule of said gland .

There are no fasciae in the facial region, since the mimic muscles are located directly under the skin . The only exception is the buccinator; This muscle is covered at the back by the high-density oropharyngeal fascia, which later becomes lax, fusing with the cheek tissue ; behind it adheres to the pterygomandibular ligament, continuing with the connective tissue that covers the pharyngeal muscles .

 

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