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31 terms

Orbit (Incomplete)

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Oribit
-->A pyramid-shaped cavity with its base directed ANTERIORLY & its apex POSTERIORLY
Major Contents of Orbit
1)***Eyeball
2)***Lacriminal Apparatus
Roof Of Orbit
-->Formed by orbital surface of FRONTAL BONE & lesser wing of sphenooid bone
-->Contents:
1)Lacrimal Fossa (w/lacriminal gland)
2)Trochlear Fossa (w/trochlear for rotation via SO muscle
Floor of Bony Orbit
-->Formed by orbital surface of MAXILLA, Zygomatic bone, and ***Oribtal process of palatine bone (seperates orbital bone from MAXILLARY SINUS; imp. in BLOW-OUT FRACTURES
Blow Out Fractures of the Bony Orbit
-->Caused by BLUNT TRAUMA to the face
-->Causes fracture to the floor of orbital cavity into the **MAXILLARY SINUS**, which causes damage to:
1)Inferior Rectus muscle
2)Infraorbital Nerve (From maxillary nerve; loss of sensation of lateral nose & upper lip
3)Infraorbital Artery (Ex. Hemorrahaging)
3)Infraorbital Artery (
Medial Wall of Orbit
-->Formed by orbital plate of
ethmoid bone, lacrimal
bone, frontal bone, and
to small degree by body
of sphenoid
-->Contents:
1)Fossa for lacriminal sac
2)Opening of nasolacriminal canal
Lateral wall of the Orbit
-->Formed by Zygomatic bone, greater wing of sphenoid, & frontal bone
Main openings into the orbital cavity
1)Optic Canal (Optic Nerve & Opthalmic Artery)
2)Superior Orbital Fissure (CN3, CN 4, CN 5 (V1), CN6, & Superior & Inferior Opthalmic Artery
3)Inferior Orbital Fissure (Maxillary Nerve & its Zygomatic Branch, & the Inferior Opthalmic Vein
Opienings Into the Orbital Cavity
Supraorbital notch -
supraorbital nerve and blood
vessels
Infraorbital canal -
infraorbital nerve and blood
vessels
Nasolacrimal canal -
nasolacrimal duct
Zygomaticotemporal and
Zygomaticofacial foramina -
corresponding nerves (CN V2)
Anterior & posterior
ethmoidal foramina -
corresponding nerves (from
nasociliary branch CN V1)
Orbital Fascia ("Periorbita")
-->Periosteum of the bones that form the orbital walls
Tenson's Capsule
-->***Fascial sheath of the eyeball
-->Represents a thin membrane that envelops the eyeball from the optic nerve to the corneoscleral junction
-->Functions:
1)Seperates the eyeball from the ORBITAL FAT
2)Pierced by the tendons of the extraocular muscles
Features of Eyelids (Palpebrae)
-->Represents thin, moveable folds of skin ant. to the eyeball; protects eye from injury & excessive light by their closure
-->Muscles involved in movement of eylid:
1)Levator Palpebrae Superior Muscle --> Elevates eylid; Inner. by Oculomotor Nerve
2)Superior Tarsal Muscle --> Assists levator palpebrae in elevating eyelid; Inner by Oculomotor Nerve
3)Obicularis Oris --> Closes eylid; Inner. by Facial Nerve
Palperbral Conjunctiva
-->Mucous membrane covering of the inner surface of the eyelids
-->Conjuctival Sac: Represents a Potential Space Created when the eye is closed betwn. the inner aspect of the eyelid & the eye
Pathway of Flow of Tears
Lacrimal gland
Lacrimal ducts
Conjunctival sac
Lacrimal lake
Lacrimal puncta
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct
Inferior nasal meatus
Nasal cavity
Parasympathetic Nerve Supply of Lacriminal Gland
1. Parasympathetic
Secretomotor innervation
comes from the ***superior
salivary nucleus (preganglionic
neuron) of the facial nerve.

Preganglionic fibers
pterygopalatine ganglion
(postganglionic neuron) via
great petrosal nerve.

Postganglionic fibers

maxillary nerve -->zygomatic
nerve --> zygomaticotemporal
nerve --> lacrimal nerve -->
lacrimal gland
Sympathetic Nerve Supply of Lacriminal Gland
2. Sympathetic

Preganglionic fibres from
intermediolateral n. T1-L2
(spinal chord) comes to
superior cervical ganglion
(sympathetic trunk) -->
postganglionic neuron

Postganglionic fibers
--> travel in
the internal carotid plexus
deep petrosal nerve
nerve to the pterygoid canal
maxillary nerve zygomatic
nerve zygomatico-temporal
nerve lacrimal nerve
lacrimal gland
Sensory Nerve Supply of Lacriminal Gland
-->Lacriminal nerve from opthalmic nerve (CN VI)
Muscles of the orbit (See Post-It or pg. 508 In Color Atlas For Method to find answers)
Nerves Of The Orbit
Optic nerve (CN II)
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Ophthalmic nerve (CN V1)
Abducens nerve (CN VI)
Ciliary parasympathetic
ganglion
Features of Optic Nerve
consists of the
axons of the
ganglion cells of
the retina

exits from the
eyeball by piercing
the sclera medial to
the posterior pole of
the eyeball &
passes through the
optic canal to enter
the middle cranial
fossa
Visual Field Defects
Branches of Opthamlmic Nerve
1)Lacriminal Nerve
-->Secretomotor fibers from communicating branch of zygomatic nerv
-->Supplies branches to conjunctiva & skin of UPPER eyelid
2)Frontal Nerves
-->Divides into supratrochlear & supraorbital nerves at the orbital margin
-->Supply the skin of the FOREHEAD & mucous membrane of the frontal sinus
3)Nasociliary Nerve
-->Communicating branch to cilliary gangilin (sensory fibers)
-->Long Cilliary Nerves (***Symp. fibers to dilator pupilae muscle)
-->Short Cilliary Nerve (***Parasym fibers to spinchter pupilae muscle)
-->Post. Ethmodial Nerve (Supplies post. ethmodial air cells AND sphenoid sir sinuses)
-->Ant. Ethmodial Nerve (Supplies mucous membrane of ant. ethmodial air sinus; appears on face as the ***EXTERNAL NASAL NERVE to suppl skin of nose down to the tip
-->Infratrochlear Nerve: Supplies the skin of the MEDIAL PART of the upper eyelid & adj part of nose
Trochlear Nerve (CN 4)
-->Enters superior oblique muscle which it supplies (through trochlear hook on medial upper area of medial orbital cavity)
Abducens Nerve
-->Runs forward on inner surface of LATERAL RECTUS muscle
Oculomotor Nerve (CN 3)
Superior branch - supplies
superior rectus and ***levator
palpebrae superioris

Inferior branch - supplies the
inferior rectus, medial rectus,
and inferior oblique

nerve to the inferior oblique
gives off a ***branch to the
ciliary ganglion that contains
***preganglionic
parasympathetic fibers
Ciliary Ganglion
It is pinhead-size
parasympathetic ganglion
situated in the posterior part of
the orbit lateral to the optic
nerve

It receives preganglionic
parasympathetic fibers from the
***oculomotor nerve (CN III)

postganglionic parasympathetic
fibers leave the ganglion via the
***short ciliary nerves and
supply sphincter pupillae
muscle and ciliary muscle
Oculotmotor Nerve Palsy ("Down & Out")
Oculomotor Nerve Palsy

External squint affects most of the
extraocular muscles

Manifestations: **COMPLETE Ptosis, **Fully DIALATED pupil, Eye is fully depressed and abducted ("down and out") due to unopposed actions of superior oblique and lateral rectus, respectively.
Trochlear Nerve Palsy ("Out & Up")
Trochlear nerve palsy

It cause paralysis of the superior oblique and
impair the ability to turn the affected eyeball
infero-medially ("up and out")

The characteristic sign of trochlear nerve injury
is*** diplopia (double vision) when looking DOWN
(e.g., when going down stairs or reading)
Abducens Nerve
Internal squint because of injury to abducens
nerve --> paralysis of lateral rectus --> inability to
abduct the affected eye

Affected eye is fully adducted by the unopposed
action of the medial rectus that is supplied by
CN I
Horner's Syndrome
-->Causes:
1)Penetrating injury to the neck
2)Panacoast Tumor
3)Thyroid Carcinoma
-->All aforementioned causes interrupt the ASCENDING PREGANGLIONIC SYMPATHETIC FIBERS ANYWHERE BTWN. THEIR ORGIN IN THE T1 segment (IML) of the spinal cord & synapse in the ***SUPERIOR CERVICAL GANGLION
-->Sign of Horner's Syndrome
1) Mioses (Constriction of the pupil)
2)Ptosis
3)Anhydrosis (Abscense of sweating)
4)Redness & increased temperature of the skin (Vasodialation)
Complete Vs. Partial Ptosis
1Complete Ptosis:
-->Due to **oculomotor nerve palsy**
-->Patient will not be able to VOLUNTARILY RAISE THE UPPER EYELID; May be associated with PUPILLARY DILATION from the loss of parasympathetic innervation of SPINCTER PUPILLAE MUSCLE
-->Presents with "Down & Out" Appearance of the eye due to the unopposed action of the SO & LR muscles

2. Partial Ptosis
-->Seen in HORNER'S SYNDROME
-->Due to loss of sympathetic innervation of the SUPERIOR TARSAL MUSCLE
-->Is Accomanied by Pupillary Constriction