The lacrimal part of orbicularis oculi is the smallest and innermost of the three parts. It is immediately surrounded by the palpebral part. It is the smallest and thinnest part of the muscle.
Also, it has the most posterior origin at the medial side of the orbit from the posterior crest and lateral surface of the lacrimal bone. Anteriorly at this point, it is seperated from the lacrimal sac by the lacrimal fascia.
It passes laterally behind the sac to diverge into two parts - upper and lower. These head into each eyelid anterior to, and partially inserting into, the tarsi. Passing laterally, they insert into the lateral palpebral raphe.
Its arterial supply is from the ophthalmic, zygomatico-orbital and angular arteries. It is innervated by the zygomatic branch of the facial nerve (VII).
The actions of the lacrimal part of orbicularis oculi are to:
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