Head Anatomy & Musculature

Head Anatomy & Musculature

The facial muscles are striated muscles that link to the skull’s bones and perform crucial processes such as mastication and facial emotions. These muscles are positioned between the ears and the coronal suture of the skull, superior to the mandible and inferior to the jaw. These muscular deficiencies can cause considerable impairment in daily activity. 

The splanchnocranium’s face muscles work in unison. The perioral face muscles, for example, are recruited at the same time as the orbicularis oris during chewing. Change the intervention pattern of the muscles of the entire face, from the superficial to the deep muscles, depending on which side you’re chewing (right, left, or central) and what you’re eating. 

To further illustrate this concept, the temporalis muscle and the buccinator muscle have a close fascial association. The buccinator’s inferior muscle fibers originate in the temporalis’ deep tendon’s anterior region. From eating to opening and moving the jaw to speech, the two muscles work together to improve their duties.

Structure and Function

The muscles of our face serve 2 major tasks for the body: mastication and facial expressions. The temporalis, medial pterygoid, lateral pterygoid, and masseter are mastication muscles (buccinator muscle is an important accessory of chewing). Facial expression is another important function. The majority of the facial muscles are involved in expressing emotions. 

The orbicularis oculi, nasalis, levator labii superioris alaeque nasi, depressor labii inferioris, procerus, auriculars, buccinator, occipitofrontalis, corrugator supercilii, risorius, depressor anguli oris, orbicularis oris, and mentalis are among these muscles. The functions of these are as follows:

  • Blinking and closing the eyelid are controlled by the orbicularis oculi. 
  • The nasalis and labii superioris alaeque nasi work by raising or “snarling” the sides of the nose. 
  • The inferior depressor labii depresses the nose. 
  • The procerus and corrugator supercilii muscles connect to the frontalis muscle between the eyebrows and are responsible for crinkling them together. 
  • The auriculars are responsible for moving the ears forward and backward from the face. 
  • The zygomaticus major and minor muscles run across the zygomatic bone and pull the muscles upward to aid in smiling. 
  • The risorius muscles are located at the corners of the mouth and help you smile.
  • The buccinator allows you to chew without biting your cheeks while also blowing air outside. 
  • With two communicating bellies, the occipitofrontalis raises the eyebrows on the face. 
  • During frowning, the depressor anguli fibers depress the sides of the mouth, and the orbicularis oris fibers purse the upper and lower lips. 
  • The inferior lip is lowered by the mentalis muscle, which is the main muscle of the lower lip. 
  • The health of the skin and mucous membranes is influenced by the superficial face muscles. 

Facial muscles have an impact on anatomical locations that are far away. The occipitofrontalis muscle, for example, has anterior anatomical continuity with the eyelid elevator and Tenon capsule, as well as posterior anatomical continuity with the sub-occipital muscles. An inappropriate tension of this myofascial continuum could negatively affect the position of the neck, the interaction between the gaze, and the posture of the head from a clinical standpoint. Through facial expression, the facial muscles intervene in speech and have a significant impact on social relationships.

Embryology

The majority of the face muscles are innervated by cranial nerve VII, which arises from the second pharyngeal arch during pregnancy. The pharyngeal arch, as well as the V3 branch of the trigeminal nerve, give rise to the mastication muscles. In each developing arch, there is a link between muscles and innervation. The pharyngeal arches were formerly referred to as branchial arches. During the fourth week of development, the arches emerge, covered in the ectoderm. The pharyngeal arch mesoderm gives rise to facial muscles. The induction of the cranial nerves in each arch is controlled by neural crest cells.

Muscles

When compared to the skeletal musculature, limbs, and trunk, the muscles of the face have distinct properties. The muscles of the face have a more complex pattern of extra fusal fiber innervation, with a higher percentage of slow type fiber. These muscles have Ruffini-like corpuscles, which are a resource for proprioception functions: different morphology but similar function when compared to the rest of the body’s skeletal muscles.

Variants in Physiology

Individuals’ face arteries may differ biologically. For surgical applications to the supplied region, this is critical. 

Nerves

The face muscles are innervated by two main nerves. The principal motor component is the facial nerve, also known as cranial nerve VII. From underneath the parotid gland, the facial nerve extends over the face. The facial nerve controls the expressive muscles, allowing a person to move their face as desired. The sensory component of the face and scalp is the trigeminal nerve, also known as cranial nerve V. Three primary branches of the cranial nerve V supply distinct parts of the face. The ophthalmic branch, also known as V1, provides blood to the forehead and leaves the skull superior to the orbits.

The V2 branch of the maxillary nerve innervates the maxilla bone area below the orbit. The mandibular branch, also known as V3, provides innervation to the area of the mandible bone below the nose. Both sensory and motor innervation of the face can be influenced by the V3 branch. The masticatory muscles are innervated by the motor component of V3. The trigeminal nerve’s three branches all contribute to the sensory innervation of the face by providing general somatic afferent fibers. The cutaneous feeling of the face is also influenced by cervical spinal nerves, but the trigeminal nerve is the predominant source of innervation.

Surgical Points to Consider

If the facial nerve is injured, it can be repaired surgically by cable grafting or primary nerve surgery. Primary nerve repair, which involves reducing tension around the anastomoses, usually yields the best results. However, because the injured nerve may only be electrically stimulated within 72 hours of injury, prompt treatment is essential.

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