Orbicularis Oris

Origin, Insertion, Action & Nerve

Attachments explained

The Orbicularis Oris is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Action & function

When the Orbicularis Oris contracts, it produces the following movement: Closes and protrudes the lips (pursing, whistling).

As part of the Facial Expression group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Orbicularis Oris receives its nerve supply from the Buccal and mandibular branches of facial nerve (CN VII).

Because a muscle can only contract when its nerve is intact, injury to the Buccal and mandibular branches of facial nerve can weaken or paralyse the Orbicularis Oris, impairing the movements it normally produces (closes and protrudes the lips (pursing, whistling)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Orbicularis Oris (the OIANS method)

Learn the orbicularis oris as the purse-string of the mouth, into which the radiating facial muscles all insert. Because its fibres encircle the oral opening, it closes and pouts the lips for whistling, kissing, and speech; picturing the many surrounding muscles pulling against this ring clarifies why the mouth has such a rich range of expressions.

Keep it in the facial-expression group supplied by the facial nerve (CN VII), specifically its buccal and mandibular branches, and contrast it with the buccinator, which shares the buccal branch but flattens the cheek rather than closing the lips. Weakness here impairs both speech and the ability to keep food and liquid within the mouth.

Frequently asked questions

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