The depressor anguli oris muscle (triangularis muscle) is a
facial muscle
The facial muscles are a group of striated skeletal muscles supplied by the facial nerve (cranial nerve VII) that, among other things, control facial expression. These muscles are also called mimetic muscles. They are only found in mammals, alth ...
. It originates from the
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
and inserts into the angle of the
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
. It is associated with
frowning
A frown (also known as a scowl) is a facial expression in which the eyebrows are brought together, and the forehead is wrinkled, usually indicating displeasure, sadness or worry, or less often confusion or concentration.
The appearance of a frow ...
, as it depresses the corner of the mouth.
Structure
The depressor anguli oris arises from the lateral surface of the
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
.
Its
fibre
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
s then converge. It is inserted by a narrow fasciculus into the angle of the
mouth
In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
.
At its origin, it is continuous with the
platysma muscle
The platysma muscle is a superficial muscle of the human neck that overlaps the sternocleidomastoid. It covers the anterior surface of the neck superficially. When it contracts, it produces a slight wrinkling of the neck, and a "bowstring" effect ...
, and at its insertion with the
orbicularis oris muscle
In human anatomy, the orbicularis oris muscle is a complex of muscles in the lips that encircles the mouth.
It is a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance ...
and
risorius muscle. Some of its fibers are directly continuous with those of the
levator anguli oris muscle, and others are occasionally found crossing from the muscle of one side to that of the other; these latter fibers constitute the
transverse muscle of the chin
The transversus menti, or transverse muscle of the chin, is a facial muscle that is often considered to be the superficial fibers of the depressor anguli oris
The depressor anguli oris muscle (triangularis muscle) is a facial muscle. It origin ...
.
The depressor anguli oris muscle receives its blood supply from a branch of the
facial artery
The facial artery (external maxillary artery in older texts) is a branch of the external carotid artery that supplies structures of the superficial face.
Structure
The facial artery arises in the carotid triangle from the external carotid arte ...
.
Nerve supply
The depressor anguli oris muscle is supplied by the
marginal mandibular branch of the
facial nerve
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...
.
Function
The depressor anguli oris muscle is a
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
of
facial expression
A facial expression is one or more motions or positions of the muscles beneath the skin of the face. According to one set of controversial theories, these movements convey the emotional state of an individual to observers. Facial expressions are a ...
.
It
depresses the corner of the mouth, which is associated with
frowning
A frown (also known as a scowl) is a facial expression in which the eyebrows are brought together, and the forehead is wrinkled, usually indicating displeasure, sadness or worry, or less often confusion or concentration.
The appearance of a frow ...
.
Clinical significance
Paralysis
Damage to the
marginal mandibular branch of the
facial nerve
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...
may cause
paralysis
Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
of the depressor anguli oris muscle.
This may contribute to an asymmetrical smile.
This may be corrected by
resecting (cutting and removing) the
depressor labii inferioris muscle
The depressor labii inferioris (or quadratus labii inferioris) is a facial muscle. It helps to lower the bottom lip.
Structure
The depressor labii inferioris muscle arises from the lateral surface of the mandible. This is below the mental foram ...
, which has a more significant impact on
smiling
A smile is a facial expression formed primarily by flexing the muscles at the sides of the mouth. Some smiles include a contraction of the muscles at the corner of the eyes, an action known as a Duchenne smile.
Among humans, a smile expresses ...
.
Hypoplasia/Aplasia
Underdevelopment (
Hypoplasia
Hypoplasia (from Ancient Greek ὑπo- ''hypo-'' 'under' + πλάσις ''plasis'' 'formation'; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a tissue or organ.Aplasia
Aplasia (; from Greek ''a'', "not", "no" + ''plasis'', "formation") is a birth defect where an organ or tissue is wholly or largely absent. It is caused by a defect in a developmental process.
Aplastic anemia is the failure of the body to produ ...
) of the depressor anguli oris can occur.Similarly to paralysis, individuals with these conditions will have an assymetric smile.
[https://www.healthline.com/human-body-maps/depressor-anguli-oris-muscle#1] These conditions are rare, and develop at or before birth (
congenitally).
See also
*
Facial muscles
The facial muscles are a group of striated skeletal muscles supplied by the facial nerve (cranial nerve VII) that, among other things, control facial expression. These muscles are also called mimetic muscles. They are only found in mammals, alth ...
*
Transverse muscle of the chin
The transversus menti, or transverse muscle of the chin, is a facial muscle that is often considered to be the superficial fibers of the depressor anguli oris
The depressor anguli oris muscle (triangularis muscle) is a facial muscle. It origin ...
Additional images
File:Depressor anguli oris animation small.gif, Position of depressor anguli oris muscle
File:Gray176.png, Mandible, outer surface, side view
File:Gray508.png, The arteries of the face and scalp
References
External links
PTCentral
{{Authority control
Muscles of the head and neck
Facial muscles