The depressor anguli oris muscle is part of the buccolabial group. It raises the angle of your mouth when smiling and helps deepen nasolabial fold.
Fibers from this muscle are embedded deep and laterally to levator labii superioris, defining the infraorbital space. Convergent with modiolus muscle at oral commissure.
Function
The levator anguli oris muscle (also referred to as caninus) is a pair of strap-like muscles located at the base of the lower jaw (mandible). They belong to a group known as buccolabial muscles; its fibers join those from other mouth muscles such as Zygomaticus major and minor, Risorius, Depressor Labii Inferioris Inferioris Mentalis for creating modiolus at the angle of mouth.
Like its counterparts, the levator anguli oris is capable of performing various actions within the mouth. When contracted, its contractions can move or lateralize lips up or down or create dimples in cheeks; all thanks to being innervated by mandibular branch of facial nerve CN VII.
This muscle is responsible for creating smiles, frown lines and other facial expressions. Food triggers its contraction while speaking or laughing can activate it further. Unfortunately, however, trauma or surgery often causes it to be injured.
Because facial expressions rely heavily on facial muscles, reconstruction using them can often be achieved. Takano et al. described a method using the levator anguli oris muscle as an anchor point for regional flap transfer into nasal defects in 1990. Under this technique, muscle is lifted via an incision in the nasolabial fold and tunneled into the nasal cavity for tunnelling into its tunneling canal. Levator anguli oris can also be utilized to raise or lower nasolabial folds, as well as other reconstructive applications. Cosmetic medicine utilizes this procedure frequently in order to enhance the look of both face and neck by reducing nasolabial folds. Furthermore, muscle can serve as a blood supply to the region which speeds healing time while also helping avoid swelling in case of injury or infection. An incision can be made into the skin to isolate muscles, while improved blood circulation is achieved by opening and widening it to allow blood flow through more freely, also helping relieve nasolabial swelling. Reducing excessive oedema allows easier maintenance of correct incision positioning during recovery.
Location
When someone frowns, the depressor anguli oris muscle is responsible for creating the downward pull on the corners of their mouth that occurs when frowning. As part of its function it receives innervation via the marginal mandibular branch of facial nerve (CN VII) as well as blood supply via inferior labial artery and mental branch of inferior alveolar artery.
The levator anguli oris is part of a larger group of muscles responsible for moving the mouth and lips – known as buccolabial group – including orbicularis oris, risorius, zygomaticus major/minor and depressor anguli oris muscles. When working together these muscles allow a variety of expressions to be achieved.
As with other facial muscles, the levator anguli oris is encased in a fibromuscular hub where its fibres attach. This structure, located at the angle of the mouth and known as the modiolus, consists of peripheral fibers of orbicularis oris and marginal fibres from levator anguli oris muscle; additionally they’re joined together through depressor anguli oris in the middle of this ring-shaped muscle that surrounds lips.
The levator anguli oris muscle can be utilized as a surgical flap during nasal reconstruction following removal of tumors in the skin of the nose. Furthermore, this muscle plays an integral part in creating the nasolabial furrow and helping prevent corners of mouth drooping when opening it. Medical conditions that may afflict the levator anguli oris include stroke, myositis, myopathy, atrophy and tears. Sometimes its operation becomes involuntary causing spasms in both cheek and mouth area. The levator anguli oris can also be affected by certain medications, including antidepressants and antipsychotics. When this is the case, it’s best to either discontinue taking them altogether or consult a physician, while continuing taking them can mean monitoring symptoms for signs of abnormalities.
Size
Depressor anguli oris (DAO) muscle is a pair of strap-like muscles extending from the base of the mandible to the angle of the mouth and is an integral component in conveying emotions such as sadness or anger; when contracted it pulls the angle of mouth downward and laterally creating frowning expression; additionally it is responsible for smiling expression.
The DAO muscle is one of the buccolabial group, comprising of the levator labii superioris alaeque nasi, risorius, zygomaticus major and minor, orbicularis oris muscle and others. Together these muscles play an integral part in facial expressions such as raising and everting of upper lips; lowering and everting lower lips; drawing down and laterally the angle of mouth as well as closing lips – among many others.
There are four insertion patterns of the incisivus labii superioris muscle in the modiolar area: In type I, fibers of ILS arise from their origins to blend with medial fibers of LAO; In type II, more than two-thirds of these ILS fibers became superficial inserting fibers for LAO; the remaining two-thirds deep inserting fibers; while in type III these ILS fibers split between superficial and deep inserting fibers before eventually merging with LAO;
Though DAO may be small, its actions are significant. Its constant downward pull can cause permanent frowning expressions or make smiling difficult; to address these problems Botox injections temporarily block nerve signals which trigger muscle contraction and give relief from frowning expressions or difficulty smiling.
Brow lifting is an effective technique used to restore a more youthful appearance, both by reducing fine lines around the brow and helping relieve headaches. It can be completed in under 30 seconds at no cost in an office environment without downtime; results typically last several months; for best results it should be repeated periodically – people with droopy or flaccid DAO should consult a plastic surgeon regarding their eligibility before beginning this treatment plan.
Variation
The Depressor Anguli Oris Muscle, commonly referred to as the Sadness Muscle, works to pull down and depress the corners of the mouth. As a paired muscle located along each side of the face starting at the edge of the chin and ending in each corner of the mouth it often serves as the focus of cosmetic surgery procedures when injured through illness or trauma.
The muscle has the shape of an inverted fan and runs along the outer side of the mandible between mental tubercle and incisor notch, connecting with other lips muscles that insert there. It plays an integral part in smiling; its absence results in flat or downturned mouth.
This muscle receives motor innervation from the marginal mandibular and buccal branches of facial nerve (CN VII). It is supplied by inferior labial artery and mental artery; additionally it drains venous blood into internal jugular vein.
Like other muscles of the face, this one is difficult to overtrain; however, damage to it is readily possible and its loss could cause an outward or inward-turning mouth and reduce your quality of life.
The levator anguli oris muscle, along with zygomaticus major and minor and the risorius, helps elevate your smile by exposing upper teeth during smiling. When dysfunctional, however, this muscle may leave your mouth looking unattractively crooked or twist.
Botox injections may provide temporary relief for an ineffective levator anguli oris muscle, though regular applications will likely be necessary in order to maintain their effects.
Researchers have observed a wide variation in the location of muscle insertion. Their research studied how these muscles attached to the angle of the mouth in 147 cadavers from both Mongoloid and Caucasian races; they discovered that rather than converging lateral to it as stated in textbooks, these muscles tend to converge above or below it instead.
