Region 5: Orbit
Apertures and Grooves
Aperture/Groove
Optic foramen and canal
Position
Posterior and medial
Superior orbital fissure
Posterior
Inferior orbital fissure
Posterio, lateral, inferior
Lacrimal fossa
Anterior, lateral, superior
Trochlear fossa
Infraorbital groove, canal,
forament
Anterior and posterior
ethmoidal foramina
Transmits/Related to:
Optic nerve and ophthalmic
artery
CN II, CN IV, CN V1, CN
VI, ophthalmic vein
Infraorbital and zygomatic
nerves and vessels
Related to lacrimal gland
Pully for superior oblique
muscle
In the orbital floor
Medial wall
Nerves and vessels of same
name
Contents of the Orbit: Soft Tissue
--Eyelids/palpebrae
*skeleton of eyelid: consists of tarsal plates
*orbital septum: attached to orbital rim
*medial and lateral palpebral ligament: attach tarsal plates to the orbital rim
*obicularis oculi muscle surrounds outer rim of orbit
*tarsal glands: secrete oily substance repelling tears from spillin over rim
*eyelashes
*lacrimal papillae
--caruncle: pink body in medial canthus
--semilunar fold/plica semilunaris: immediately lateral to the caruncle
--palpebral fissure
*canthus: medial or lateral angles of the palpebral fissure
*lacus lacrimalis: space for accumulation of tears
Contents of Orbit: Eyeball and Muscles
--Eyeball and its Sheath
*bulbar fascia/Tenon’s capsule: fascia surrounding eyeball
*suspensory ligament: hammock shaped thickening of bulbar fascia under
eyeball
*check ligaments: expansion of muscle sheaths to orbit wall
--Extrinsic Eye Muscles (origin from common tendinous ring)
*superior rectus: elevates and adducts the eye/pupil up and in
*inferior rectus: depresses and adducts the eye/pupil down and in
*lateral rectus: abducts the eye/pupil moves laterally
*medial rectus: adducts the eye/pupil moves medially
--Oblique Eye Muscles
*superior oblique: origin on sphenoid bone, above and medial to tendinous
ring
--depresses and abducts the eye/pupil down and out
*inferior oblique: origin is anterior, inferior, and medial in floor of orbit
--elevates and abducts the eye/pupil up and out
--Levator Palpebrae Superioris Muscle
O Above tendinous ring on sphenoid bone
I Superior tarsal plate
Also attached to tarsal plate by Muller’s/tarsal muscle that is smooth muscle and
inn. by sympathetic nerves
Not
--loss of sympathetic supply to head causes partial ptosis
--loss of oculomotor nerve causes full ptosis
Arteries and Veins
--ophthalmic artery
*From: internal carotid artery and enters orbit through optic foramen
*Supplies:
a. retina (via central artery)
b. extrinsic muscles
c. eyeball (via anterior and posterior ciliary arteries)
d. lacrimal gland
--ophthalmic vein: drains into cavernous sinus; communicates with veins on face
--infraorbital artery and vein: on floor of orbit
Lacrimal Apparatus: tears flow from gland to inner canthus of eye
--Lacrimal gland
*lacrimal ducts: drains both parts of the gland
*stimulated by parasympathetic fibers from pterygopalatine ganglion
--Conjunctival sac
*tears from gland spread over cornea
--Lacrimal lake: place for tears to accumulate
--Lacrimal papilla: near medial angle of the eye
--Lacrimal puncta: hole in lacrimal papilla
--Lacrimal canaliculi: small canals emptying into lacrimal sac
--Lacrimal sac: upper end of nasolacrimal duct
--Nasolarimal duct: tears drain through opening in inferior meatus of the nasal
cavity
Cranial Nerves Related to Orbit
--Optic Nerve (CN II): SENSORY
*exits the orbit thorugh optic foramen
*it is entered by the central artery of the retina
--Oculomotor Nerve (CN III): MOTOR with PARASYMPATHETIC fibers
*enters through superior orbital fissure as superior and inferior divisions
and passes through the common tendinous ring
--Superior Division: inn. sup. rectus and levator palpebrae superioris
--Inferior Division:
a. inn. med. rect, inf. rect, inf. oblique
b. sends branches w/ preganglionic parasympathetic fibers to
ciliary ganglion
--Trochlear Nerve (CN IV): MOTOR
*enters orbit through superior orbital fissue outside the common tendinous
ring
*Inn: superior oblique m.
--Trigeminal Nerve: Ophthalmic Divison (CN V1): SENSORY
*enters the orbit as 3 branches
a. lacrimal branch
--enters orbit through superior orbital fissure outside of ring
--receives postganglionic parasympathetic fibers from
zygomatic n. for lacrimal gland
--sensory to skin of upper eyelid
b. frontal branch
--enters orbit through superior orbital fissure outside ring
--divides into supraorbital and supratrochlear n. to supply skin
c. nasociliary branch
--enters orbit through superior orbital fissure through ring
--sends sensory fibers to eye through long and short ciliary nn.
--terminal branches include: posterior ethmodial n, anterior
ethmodial n, and infratrochlear n.
--Abducens Nerve (CN VI): MOTOR
*enters orbit thorugh superior orbital fissure through ring
*Inn: lateral rectus
Nervous Supply: Ciliary Ganglion
--parasympathetic PREganglionic axons from oculomotor nerve SYNAPSE here
*POSTganglionic axons pass from ganglion to eye through short ciliary
nerves
*motor fibers to ciliary muscle for accommodation and the sphincter pupillae
muscle to constrict the pupil are due to parasympathetics
--sympathetic vasomotor and pupillo-dilator axons pass through the ganglion
without synapsing (these travel in the long ciliary nerves)