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Depressor anguli oris muscle: want to learn more about it?

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Depressor anguli oris muscle

Depressor anguli oris muscle (Musculus depressor anguli oris)

Depressor anguli oris is a paired triangular muscle that extends from the mental tubercle of mandible to the angle of the mouth. It belongs to the buccolabial group of facial muscles along with levator labii superioris alaeque nasi, levator labii superioris, zygomaticus major, zygomaticus minor, levator anguli oris, risorius, depressor labii inferioris, mentalis, orbicularis oris, incisivus superior, incisivus inferior and buccinator muscles.

The muscle is situated lateral to the chin on each side, extending almost vertically upwards. Along with other muscles that attach at the angle of the mouth, depressor anguli oris forms a fibromuscular structure called modiolus.

As its name suggests, it depresses (depressor) the angle of the mouth (anguli oris) and pulls it slightly laterally. Thereby, it facilitates expressing sadness and assists in opening the mouth. 

Key facts about depressor anguli oris muscle
Origin Mental tubercle and oblique line of mandible (continuous with platysma muscle)
Insertion Modiolus
Function Depresses angle of mouth
Innervation Buccal and mandibular branches of facial nerve (CN VII)
Blood supply Inferior labial artery (facial artery); mental artery (maxillary artery)

This article will teach you all you need to know about the anatomy and functions of depressor anguli oris muscle.

Origin and insertion

Depressor anguli oris originates from the oblique line and mental tubercle of mandible located on the anterior aspect of the bone. The muscle fibers converge into a narrow fascicle running superiorly towards the angle of the mouth. It then blends with other muscles that insert into the lips. On the point where all of these muscles converge and interlace they form a dense, mobile, fibromuscular mass called the modiolus. It is not entirely clear which muscles exactly attach to the modiolus, but some of the certain ones include depressor anguli oris, buccinator, risorius, zygomaticus major and orbicularis oris muscles.

Some fibers of the depressor anguli oris muscle can continue below its origin point at the mental tubercle and cross the midline to blend with the contralateral fibers. These particular fibers form the transversus menti muscle, also called the “mental sling”.

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Relations

Depressor anguli oris arises from the anterior side of the mandible as one of the superficial layer muscles of the buccolabial group. The distal part of the muscle courses over the lateral border of depressor labii inferioris. Inferiorly, depressor anguli oris is continuous with the platysma muscle and cervical fascia.

Innervation

Depressor anguli oris receives motor innervation from marginal mandibular and buccal branches of facial nerve (CN VII).

Blood supply

Depressor anguli oris is supplied by the inferior labial and mental arteries, which are branches of the facial artery and maxillary artery, respectively. The venous blood is drained through the facial vein into the internal jugular vein.

Function

Depressor anguli oris pulls the angle of the mouth inferolaterally. Its action plays an important part in facial expression, as it helps expressing feelings of sadness or anger. This is why depressor anguli oris is deemed one of the “frowning muscles”, along with muscles such as corrugator supercilii, procerus and orbicularis oris. Depressor anguli oris also aids in functions such as opening the mouth while speaking or eating. While opening the mouth, the action of depressor anguli oris modifies the mentolabial sulcus, making it deeper and more horizontal.

Depressor anguli oris muscle: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 1,300,460 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
  • Palastanga, N., & Soames, R. (2012). Anatomy and human movement: structure and function (6th ed.). Edinburgh: Churchill Livingstone.
  • Standring, S. (2016). Gray's Anatomy (41tst ed.). Edinburgh: Elsevier Churchill Livingstone.
  • Singh, V. (2014). Textbook of Anatomy (Regional and Clinical) Head, Neck, and Brain; Volume III. London: Elsevier Health Sciences APAC.
  • Watanabe, K., Loukas, M. (2016). Anatomy for Plastic Surgery of the Face, Head, and Neck. New York: Thieme Medical Publishers, Inc.

Illustrators:

  • Depressor anguli oris muscle (Musculus depressor anguli oris) - Yousun Koh
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