Orbit (Incomplete)

Terms	Definitions
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