Anatomy
Origin:
Mandible below and maxilla above, some fibres originate from other muscles of the face (buccinator, depressor anguli oris, zygomaticus major and minor, quadratus labii inferioris and superioris)
Insertion:
The skin of the lips and the mucous membrane beneath the lips.
Key Relations:
Fibres completely encircle the mouth.
Functions
-Acts in the manner of a sphincter around the mouth narrowing the mouth and closing the lips.
e.g. as in closing the mouth.
-It can also pull the lips towards the teeth through the action of its deep and oblique fibres.
-When all fibres act together the lips are protruded.
e.g. puckering the lips in kissing or whistling..
Supply
Nerve Supply:
Buccal and mandibular branches of the facial nerve (CN 7).
Blood Supply:
-Superior and inferior labial branches of facial artery
-Mental and infra orbital branches of the maxillary artery
–Superficial temporal artery.
Clinical
A genetic abnormality can cause babies to be born without all or part of the orbicularis oris muscle. When part of the muscle is missing it may often be recognised by a slight drooping of the face or asymmetrical facial movements especially when smiling or crying.
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