Facial muscles

FACE AND FACIAL MUSCLES

Face Skin Superficial Fascia Cleavage Lines Facial Muscles Functional Groups Muscles Modiolus Expressions

1 Face

Face (or countenance) extends:

  • Superiorly → from the adolescent position of hairline.
  • Inferiorly → to the chin and base of mandible.
  • On each side → to the auricle.

Forehead is therefore common to both the face and scalp.

2 Skin of the Face

1. Vascularity

  • Facial skin is very vascular.
  • Rich vascularity makes the face:
    • Blush.
    • Blanch.
  • Wounds of the face bleed profusely but heal rapidly.
  • Results of plastic surgery on the face are excellent for the same reason.

2. Glands

Facial skin is rich in:

  • Sebaceous glands → keep the face oily; may also cause acne in young adults.
  • Sweat glands → help in regulation of body temperature.

3. Laxity of Skin

  • Greater part of facial skin is lax.
  • Facilitates rapid spread of oedema.
  • Renal oedema appears first in the eyelids and face before spreading to other parts of the body.

4. Skin of Nose and Ear

  • Boils in the nose and ear are acutely painful due to the fixity of skin to the underlying cartilage.

5. Elasticity and Thickness

  • Facial skin is very elastic and thick because facial muscles are inserted into it.
  • Wounds of the face therefore tend to gape.

3 Superficial Fascia of Face

It contains:

  1. Facial muscles
    • All are inserted into the skin.
  2. Vessels and nerves
    • To the muscles and skin.
  3. Variable amount of fat
    • Fat is absent from the eyelids.
    • Well developed in the cheeks.
    • Forms buccal pads.
    • Buccal pads are very prominent in infants and help in sucking.

Deep Fascia

  • Deep fascia is absent from the face except:
    • Over parotid gland → forms parotid fascia.
    • Over buccinator → forms buccopharyngeal fascia.

4 Cleavage Lines of Skin in the Face

  • Cleavage lines or Langer lines of skin tension are topological lines produced due to:
    • Parallel orientation of collagen fibres in the dermis.
    • Underlying muscle.
  • Karl Langer → Austrian anatomist, 1819–1887.
  • Orientation of cleavage lines in facial skin is region-specific.

Natural Wrinkle Lines

  • Result from repeated folding of skin perpendicular to the long axis of the underlying contracting muscle of facial expressions.
  • Wrinkle lines become prominent in elderly due to loss of skin elasticity.

For excision of skin lesions such as:

  • Scars.
  • Pigmented patches.
  • Skin cancers.

Incisions along natural wrinkle lines or cleavage lines produce less scarring.

5 Facial Muscles

  • Facial muscles are subcutaneous muscles.

Peculiarities of Facial Muscles

  1. Since these muscles are inserted into the skin:
    • They bring out various facial expressions.
    • Hence, they are also called muscles of facial expression.
    • They have small motor units.
  2. Embryologically:
    • Develop from mesoderm of the 2nd branchial arch.
    • Therefore, supplied by the facial nerve.
  3. Morphologically:
    • Represent the best remnants of the panniculus carnosus.
    • Panniculus carnosus is a continuous subcutaneous muscle sheet seen in some animals.
    • All facial muscles are inserted into the skin.
  4. Topographically, muscles are grouped under six heads.
  5. Functionally:
    • Most can be regarded primarily as regulators of three openings of the face:
      1. Palpebral fissures.
      2. Nostrils.
      3. Oral fissure.
    • Each opening has:
      1. A single sphincter.
      2. A variable number of dilators.
    • Sphincters are naturally circular.
    • Dilators are radial.

These muscles are better developed around the eyes and mouth than around the nose.

6 Functional Groups of Facial Muscles

A. Palpebral Fissure

Sphincter → Orbicularis oculi.

Dilators:

  1. Levator palpebrae superioris.
  2. Frontalis part of occipitofrontalis.

B. Oral Fissure

Sphincter → Orbicularis oris.

Dilators → all muscles around the mouth except:

  • Orbicularis oris.
  • Sphincter.
  • Mentalis, which does not mingle with orbicularis oris.

C. Nostrils

Sphincter → Compressor naris.

Dilators:

  1. Dilator naris.
  2. Depressor septi.
  3. Medial slip of levator labii superioris alaeque nasi.

7 Other Muscles of Face

Muscles of Scalp

  • Occipitofrontalis → described under scalp.

Muscles of Auricle

  • Situated around the ear.
  • These are vestigial muscles:
    1. Auricularis anterior.
    2. Auricularis superior.
    3. Auricularis posterior.

Muscles of the Eyelids / Orbital Openings

  1. Corrugator supercilii
  2. Orbicularis oculi
  3. Levator palpebrae superioris
    • Extraocular muscle.
    • Supplied by sympathetic fibres and the third cranial nerve.

Muscles Around Nasal Opening

  1. Procerus
  2. Compressor naris
  3. Dilator naris
  4. Depressor septi

Muscles Around the Mouth

  1. Orbicularis oris
  2. Buccinator
  3. Levator labii superioris alaeque nasi
  4. Zygomaticus major
  5. Levator labii superioris
  6. Levator anguli oris
  7. Zygomaticus minor
  8. Depressor anguli oris
  9. Depressor labii inferioris
  10. Mentalis
  11. Risorius

8 Muscles of Facial Expression — Origin, Insertion and Action

1. Corrugator Supercilii

Origin

  • Medial end of superciliary arch.

Insertion

  • Skin of mid-eyebrow.

Action

  • Produces vertical lines on forehead.
  • Causes frowning.

2. Orbicularis Oculi

Parts

  1. Orbital part
    • On and around the orbital margin.
  2. Palpebral part
    • In the lids.
  3. Lacrimal part
    • Lateral and deep to the lacrimal sac.

Origin

  • Orbital part: medial part of medial palpebral ligament, frontal process of maxilla and nasal part of frontal bone.
  • Palpebral part: lateral part of medial palpebral ligament.
  • Lacrimal part: lacrimal fascia and posterior lacrimal crest; forms sheath for lacrimal sac.

Insertion

  • Orbital part → concentric rings return to point of origin.
  • Palpebral part → lateral palpebral raphe.
  • Lacrimal part → passes laterally in front of tarsal plates of both eyelids.

Actions

Orbital part:

  • Protects eye from bright light, wind and rain.
  • Causes forceful closure of eyelids.

Palpebral part:

  • Closes lids gently as in blinking and sleeping.

Lacrimal part:

  • Dilates lacrimal sac for sucking of lacrimal fluid into the lacrimal sac.
  • Directs lacrimal puncta into the lacrimal sac.
  • Supports the lower lid.

3. Procerus

Origin

  • Nasal bone and upper part of superior nasal cartilage.

Insertion

  • Skin of forehead between eyebrows and on bridge of nose.

Action

  • Causes transverse wrinkles.

4. Compressor Naris

Origin

  • Maxilla just lateral to nose.

Insertion

  • Aponeurosis across dorsum of nose.

Action

  • Compresses nasal aperture.

5. Dilator Naris

Origin

  • Maxilla over the lateral incisor.

Insertion

  • Alar cartilage of nose.

Action

  • Dilates nasal aperture.

6. Depressor Septi

Origin

  • Maxilla over the medial incisor.

Insertion

  • Lower mobile part of nasal septum.

Action

  • Pulls nose inferiorly.

7. Orbicularis Oris

Structure

  • Comprises four quadrants:
    1. Upper.
    2. Lower.
    3. Right.
    4. Left.
  • Each quadrant consists of:
    1. Large pars peripheralis.
    2. Small pars marginalis.

Insertion

  • Pars peripheralis → extrinsic fibres converge at the modiolus, where they form triangular sheets going to each lip.
  • Pars marginalis → fibres extend to the vermilion zone, where they interdigitate with fibres of the opposite side.

Action

  • Closes lips.
  • Protrudes lips.
  • Fibres interdigitate with numerous extrinsic muscles opposite side, making it most versatile for various types of grimaces.
  • This part is associated with speech and helps in producing musical tones.

8. Buccinator

Muscle of the cheek.

Pierced by:

  1. Parotid duct.
  2. Buccal branch of mandibular nerve.

Origin

  1. Upper fibres → maxilla opposite molar teeth.
  2. Lower fibres → mandible opposite molar teeth.
  3. Middle posterior fibres → pterygomandibular raphe attached to pterygoid hamulus and inner aspect of mandible behind 3rd molar tooth.

Insertion

  1. Upper fibres → straight to upper lip.
  2. Lower fibres → straight to lower lip.
  3. Middle fibres:
    • Decussate.
    • Upper fibres go to lower lip.
    • Lower fibres reach upper lip.

Action

  • Flattens cheek against gums and teeth.
  • Prevents accumulation of food in the vestibule.
  • It is the whistling muscle.

9. Levator Labii Superioris Alaeque Nasi

Origin

  • Frontal process of maxilla.

Insertion

  • Upper lip and alar cartilage of nose.

Action

  • Lifts upper lip.
  • Dilates the nostril.

10. Zygomaticus Major

Origin

  • Posterior aspect of lateral surface of zygomatic bone.

Insertion

  • Skin at angle of mouth.

Action

  • Pulls angle of mouth upwards as in smiling and laughing.

11. Levator Labii Superioris

Origin

  • Infraorbital margin of maxilla.

Insertion

  • Skin of upper lateral half of upper lip.

Action

  • Elevates upper lip.
  • Forms the nasolabial groove.

12. Levator Anguli Oris

Origin

  • Maxilla just below infraorbital foramen.

Insertion

  • Skin at angle of mouth.

Action

  • Elevates angle of mouth.
  • Forms the nasolabial groove.

13. Zygomaticus Minor

Origin

  • Anterior aspect of lateral surface of zygomatic bone.

Insertion

  • Upper lip medial to its angle.

Action

  • Elevates the upper lip.

14. Depressor Anguli Oris

Origin

  • Oblique line of mandible below first molar, premolar and canine teeth.

Insertion

  • Skin at angle of mouth.
  • Fuses with orbicularis oris.

Action

  • Draws angle of mouth downwards and laterally.

15. Depressor Labii Inferioris

Origin

  • Anterior part of oblique line of mandible.

Insertion

  • Lower lip at midline.
  • Fuses with muscles from opposite side.

Action

  • Draws lower lip downward.

16. Mentalis

Origin

  • Mandible inferior to incisor teeth.

Insertion

  • Skin of chin.

Action

  • Elevates and protrudes lower lip.
  • Wrinkles skin on chin.

17. Risorius

Origin

  • Fascia on the masseter muscle.

Insertion

  • Skin at angle of mouth.

Action

  • Retracts angle of mouth.

18. Platysma

Origin

  • Upper parts of pectoral and deltoid fasciae.
  • Fibres run upwards and medially.

Insertion

  • Anterior fibres → base of mandible.
  • Posterior fibres → skin of lower face and lip.
  • May be continuous with risorius orfright.

Action

  • Releases pressure of skin on subjacent veins.
  • Depresses mandible.
  • Pulls angle of mouth downwards as in horror or fright.

9 Modiolus

  • Modiolus is a compact, mobile fibromuscular structure.
  • Present about 1.25 cm lateral to the angle of the mouth, opposite the upper second premolar tooth.

Muscles Forming the Modiolus

Five muscles interlace to form the modiolus:

  1. Zygomaticus major.
  2. Buccinator.
  3. Levator anguli oris.
  4. Risorius.
  5. Depressor anguli oris.

10 Common Facial Expressions and Muscles Producing Them

1. Surprise → Frontalis.
2. Dislike → Corrugator supercilii + Procerus.
3. Anger → Dilator naris + Depressor septi.
4. Smiling and laughing → Zygomaticus major.
5. Grinning → Risorius.
6. Sadness → Levator labii superioris + Levator anguli oris.
7. Grief → Depressor anguli oris.
8. Closing the mouth → Orbicularis oris.
9. Whistling/kissing → Buccinator + Orbicularis oris.
10. Doubt → Mentalis.
11. Horror, terror and fright → Platysma.