The Orbit
Terms
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- what is the blinker muscle of the eyelid? what is it innervated by?
- orbicularis oculi, facial N
- what is the elevator muscle of the upper eyelid?
- levator palpebrae superioris
- what are the two parts of the levator palpebrae superioris?
- striated part and smooth part (superior tarsal M)
- what innervates the striated part of the levator palpebrae?
- occulomotor N (CN III)
- what innervates the smooth part of the levator palpebrae (aka superior tarsal M)?
- sympathetic NS
- ptosis
- drooping of the eyelid, can be caused by a lesion of the sympathetic NS
- what does the subcutaneous tissue of the eyelids contain?
- the eyelashes, their associated sebaceous glands (of Zeiss) and modified sweat glands (of Moll)
- what are the 5 layers of the eyelid?
- skin, subcutaneous connective tissue, muscular layer, tarsofascial plane, conjunctiva
- where is the lacrimal gland located?
- in the supero-lateral corner of the orbit
- how many bones make up the orbit?
- seven
- where is the superior orbital fissure located?
- between the greater and lesser wings of the sphenoid bone
- what makes up most of the medial wall of the orbit?
- ethmoid bone
- the orbital aperture is formed by . . .
- the frontal bone superiorly, the maxilla inferiorly and medially, and the zygomatic bone laterally
- how many extraocular muscles are there?
- 6
- describe the origen of the extraocular muscles
-
the 4 rectus muscles arise from a fibrous ring called the annulus tendineus
the 2 oblique muscles arise separate from the rectus muscles -- the superior oblique M arises a little below and medial to the levator palpebrae superioris, both just above the annulus tendineus. The inferior oblique M arises in the anterior part of the floor of the orbit, from a fossa on the maxilla - innervation of extraocular muscles
-
all except 2 are innervated by the oculomotor nerve (CN III)
(LR)6(SO)4 (LR Sulfate)
Lateral Rectus (CN VI)
Superior Oblique (CN IV) - test for trochlear nerve paralysis
-
ask patient to look in and then down
if can't do it trochlear nerve is probably lesioned - what are the three branches of the opthalmic nerve?
- lacrimal, frontal, nasociliary
- what does the nasociliary nerve go through?
- annulus tendineus
- what is the most significant branch of the ophthalmic artery
- central retinal artery
- superior division of the oculomotor nerve
- innervates the superior rectus and levator palpebrae superioris muscles
- inferior division of the oculomotor nerve
- innervates the other 3 extraocular muscles that are not innervated by the trochlear and abducens nerves (i.e. the inferior rectus, medial rectus, and inferior oblique muscles)
- contraction of the pupil of the eye in the "light reflex"
- uses the optic nerve as the "afferent limb" and the oculomotor nerve, ciliary ganglion, and short ciliary nerves as the "efferent limb" to constrict the pupil
- what are the three roots of the ciliary ganglion?
-
"motor root" (from inferior division of the oculomotor N)
"sensory root" (branch of the nasociliary N)
"sympathetic root" (from the deep petrosal N, carries the postganglionic fibers that travel from the superior cervical ganglion along the carotid plexus)