Orbital part of orbicularis oculi

The orbital part of orbicularis oculi is the thick, peripheral portion of this circular orbicularis oculi muscle that surrounds the orbital margin. It is primarily responsible for forceful closure of the eyelids.

Anatomical Description

1. Origin

• Nasal part of the frontal bone

• Frontal process of the maxilla (in front of the lacrimal groove)

• Medial palpebral ligament (anterior surface and borders)

2. Course and structure

• Fibres sweep laterally and superiorly, encircling the orbital rim to form a complete elliptical loop with no interruption at the lateral palpebral commissure.

• Upper fibres blend superiorly with the frontalis and corrugator supercilii muscles, while inferior fibres extend downward onto the cheek.

• The muscle forms a broad, reddish layer lying superficial to the orbital septum and deep to the subcutaneous tissue.

3. Insertion

The fibres interlace laterally with those from the opposite side at the lateral palpebral commissure and blend with neighbouring facial muscles.

Innervation

Temporal and zygomatic branches of the facial nerve (cranial nerve VII).

Blood Supply

Branches of the facial, superficial temporal, and ophthalmic arteries (notably the supraorbital and infraorbital branches).

Actions

The orbital part of orbicularis oculi muscle causes forceful eyelid closure (squinting, reflex protection from light, wind, or foreign bodies). It also assists the palpebral part during voluntary or reflex eye closure.