Objective
Describe the muscles of eye lid, their actions and innervations.
Muscles of eyelid: Their Actions and Innervations
The
muscles of the eyelids are:
Levatorpalpebræsuperioris (LPS)
Orbicularis oculi
Corrugator
The Levator palpebrae superioris is thin, flat, and
triangular in shape. It arises from the under surface of the small wing of the
sphenoid, above and in front of the optic foramen, from which it is separated
by the origin of the Rectus superior.
o Nerve:
supplied by the oculomotor nerve
o Action:
it raises the upper eyelid, on contraction.
The Orbicularis oculi occupies the eyelids or
palpebrae, surrounds the circumference of the orbit, and spreads over the
temple, and downward on the cheek. It has the following portions:
i) The palpebral portion of the muscle is
thin and pale; it arises from the bifurcation of the medial palpebral ligament.
ii) The orbital portion is thicker and of a
reddish color; its fibers form a complete ellipse without interruption at the
lateral palpebral commissure.
iii) The lacrimal part (Tensor tarsi) is a
small, thin muscle, about 6 mm. in breadth and 12 mm. in length, situated
behind the medial palpebral ligament and lacrimal sac.
The Corrugator supercilii is a small, narrow,
pyramidal muscle, placed at the medial end of the eyebrow, beneath the
Frontalis and Orbicularis oculi. It arises from the medial end of the
superciliary arch.
Nerves:
The Orbicularis oculi and Corrugator are supplied by the facial nerve.
Actions:
The Orbicularis oculi is the sphincter
muscle of the eyelids. The Levator palpebrae superioris is the direct
antagonist of this muscle.
The Corrugator draws the eyebrow
downward and medialward, producing the vertical wrinkles of the forehead. It is
the “frowning” muscle, and may be regarded as the principal muscle in the
expression of suffering.
REFERENCES:
Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):
Gray's Anatomy
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy