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

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