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UKCD ANA534 Orbit

learning objective answers to orbit

xWhat is the function of lacrimal gland and nasolacrimal duct? The lacrimal gland secretes tears, the eyelids sweep them across the eye medially where the nasolacrimal duct drains them into the nasal cavity.
What is the function of the superior tarsal muscle? It gives the upper eyelid “tone” keeping it elevated above the iris of the eye.
What is the innervation of the superior tarsal muscle? It is innervated by the sympathetic division of the ANS.
What is the function of the tarsal gland? It secretes a waxy material to keep eyelids from sticking together when closed.
What is a sty? It is a blocked ciliary gland.
What is the common tendinous ring (annular ring)? A circular tendon at the apex of the orbit to which all the extraocular mm. except the inferior oblique take origin.
List the innervation of all the extraocular muscles? Lateral rectus - CN VI (abducens); superior oblique - CN IV (trochlear); all others - CN III (oculomotor).
Describe the action of each extraocular m. on the direction of the iris. Lateral rectus - aBduction; medial rectus - aDduction; superior rectus - laterally and upward; inferior rectus - laterally and downward; superior oblique - medially and downward; inferior oblique - medially and upward.
How would you specifically test each muscle for integrity? Ask the patient to look Lateral rectus - aBduction; medial rectus - aDduction; superior rectus - laterally and upward; inferior rectus - laterally and downward; superior oblique - medially and downward; inferior oblique - medially and upward.
How would a lesion of cranial n. VI appear? In a lesion of the abducens nerve (VI) no aBduction is possible.
How would a lesion of cranial n. IV appear? In a lesion of the trochlear nerve (IV) no medial depression is possible PLUS intortion is not possible resulting in double vision and patient tilting his head to minimize this.
How would a lesion of cranial n. III appear? In a lesion of the oculomotore nerve (III) no aDduction is possible among other movements.
What is extorsion/intorsion? These are movements involving the rotation of the eyeball around its visual axis (with eyeball NOT in its LOP).
Which muscle(s) are responsible for extorsion? The superior oblique = intortion (rotation toward nose from above)
Which muscle(s) are responsible for intorsion? The inferior oblique = extortion (rotation toward the nose from below).
What is the function of these movements (extorsion/intorsion)? To keep image viewed level regardless of the angle of tilt of the head.
Name the 3 layers of the eyeball From the external aspect inward they are the sclera; the choroid and the retina (innermost).
Which layer of the eye contains the photoreceptor cells? The retina.
What is the optic disc? The site where the optic nerve attaches to the eye - no vision (photoreceptor cells) here.
What is the macula lutea? A circular area adjacent to the optic disc yellowish in color with a central depressed spot - the fovea centralis.
Why would you stay away from the fovea centralis when using a laser to reattach 
the retina? It is the site of most acute vision on the retina.
What are the ciliary processes? The ciliary processes continually produce aqueous humor.
What is the significance of the ciliary processes to vision? The suspensory ligament of the lens arises from the edge of the ciliary process. Curvature of the lens (contraction or relaxation of the suspensory ligament) functions to focus light differing amounts of light on the retina.
What is glaucoma? An increased pressure of aqueous humor in the anterior chamber of the eye.
What is the anatomical basis for development of this disorder? Aqueous humor, constantly produced in the ciliary body, is not drained into the venous sinuses due to compression of these thin-walled vessels as a result of the increased pressure exterted by the abnormal amount of aqueous humor present in the chamber.
What are the3 major branches of V1 in the orbit? From medial to later the intra-orbital branches of V1 are: the nasolacrimal n., the frontal n., and the lacrimal n.
What is/are the major modalities of all 3 of these branches? All 3 branches of V1 are general sensory only in modality.
Where does the autonomic innervation for the orbit come from (symp/parasymp)? Sympathetic from superior cervical ganglion via hitch-hiking along V1 (nasociliary); parasympathetic from CN III.
What types of fibers do the long ciliary nn. carry? Postganglionic sympathetic fibers only.
What types of fibers do the short ciliary nn. Carry? Postganglionic sympathetic AND parasympathetic fibers.
What controls pupil dilation? Contraction? Dilation of the pupil is a sympathetic response, contraction is parasympathetic
How does the lacrimal gland get it’s vasomotor (secretory) innervation. Vasomotor (secretory) innervation for the lacrimal gland comes from CN VII where the preganglionic parasympathetic fibers travel to the pterygopalatine ganglion via the greater petrosal n.
Where do the sympathetic fibers come from? The parasympathetic fibers? Both postganglionic sympathetic and parasympathetic fibers travel from the pterygopalatine ganglion to the lacrimal gland via the zygomatic n. of V2 to the lacrimal gland.
Which vessel supplies all the structures of them orbit? The ophthalmic artery.
Through what opening does this vessel access the orbit? The optic canal.
Which vessel supplies the retina? The central artery of the retina - a branch of the ophthalmic a.
Name two nerves/vessels that exit the orbit to supply the forehead and anterior scalp. The supraorbital and supratrochlear aa. and nn.
Created by: wiechartm



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