ORBIT Flashcards
Name the bones that make up the orbit
Frontal, zygomatic, maxilla, lacrimal, ethmoid, sphenoid
Name the layers that constitute the eyelid- from superficial to deep
Skin Subcutaneous tissue Orbicularis oculi Orbital septum Tarsus Conjunctiva
Where can fluid accumulate after eye trauma
Subcutaneous layer, causing racoon eye
What nerve damage may cause inability to close the eyelid and what muscle is effected
Frontotemporal branch of facial nerve.
Orbicularis occuli
What nerve damage may cause ptosis and what muscles are effected
Occulomotor nerve supplying Levator palpebrae
Sympathetic fibres supplying superior tarsal (can get ptosis following sympathetic dissection for excessive sweating)
Name the neurovascular structures that enter and exit the orbital cavity through the optic canal (2)
Ophthalmic artery
Optic verve
Name the neurovascular structures that enter and exit the orbital cavity through the superior orbital fissure (8)
Superior ophthalmic vein Lacrimal branch of V1 Frontal branch of V1 CIV Superior branch of CIII Nasocilliary branch of V1 CVI Inferior branch of CIII
Name the neurovascular structures that enter and exit the orbital cavity through the inferior orbital fissure (4)
Infraorbital vein
Infraorbital artery
Maxillary branch of V2
Vein to pterygoid plexus
Describe the common tendinous ring
A thickening of the periosteum in the posterior part of the orbit. Surrounds optic canal and central part of superior orbital fissure. Point of origin of the extra ocular muscles (rectus)
Name the 7 extrinsic muscle and their innervations
Levator palpebrae superious (CIII) Superior rectus (CIII) Inferior rectus (CIII) Medial rectus (CIII) Lateral rectus (CVI) Superior oblique (CIV) Inferior oblique (CIII)
What is the blood supply to the orbital cavity
Ophthalmic artery branched from internal carotid
What muscles make up the common tendonous ring
The four rectus muscles
What neuromuscular structures are found in the common tendonous ring
Optic nerve, opthlamic artery, inferior and superior division of oculomotor, nasocilliary, abducenct
What are the constituents of the lacrimal apparatus
Lacrimal gland, lacrimal canaliculi, lacrimal sac, nasolacrimal duct
Where does the lacrimal gland sit
Lateral superior aspect of eye. Split in two by the tendon of elevator palpebrae superioris
Where does the lacrimal sac sit
On the lacrimal fossa on the medial side
What is dacryocystocele
A congenital condition whereby the nasolacrimal duct is closed. When cry fills up with tears balloons out of nostril
What supplies the lacrimal gland
The lacrimal branch of the ophthalmic artery
Venous drainage of orbit
Superior and inferior ophthalmic veins
What extrinsic muscle are not innervated by occulomotor
Lateral rectus and superior oblique
What innervate palpebrae levator superiors and what happens if its damages
Superior branch of CIII. Complete ptosis
If there is damage to medial orbit (around cribriform plate) what muscle maybe affected
Superior oblique.
Describe superior oblique
Two bellies. origin just outside of tendonous ring, sling in medial orbit attaches to eye. Innervated by trochlea. Moves eyeball down and medially
Ophthalmic nerve branches
Lacrimal nerve
Frontal nerve
Nasociliary nerve
What may occur with superior orbital fracture
Frontal nerve splits into two branches which both exit the orbit around the superior obit to innervate skin on eyelid forehead and scalp. May get numbness if damaged.
Describe the path of the ophthalmic nerve until it branches
From trigeminal ganglion. V1 divides into three frontal, lacrimal and nasociliary just before the orbit. Frontal and lacrimal enter orbit outside of tendons ring, nasocillary within. All via superior orbital fissure.
Describe the path of the lacrimal branch of V1 after entering orbit
Goes to lacrimal duct traveling superior to lateral rectus.
Describe path of frontal branch of V1 after entering the orbit
Frontal sensory to face outside orbit. Travels superior to levator palpebrae superioris branches into two supratrochlear and supraorbital. Both exit the skull through supraorbital notch/ foramina and innervate eyelid skin and forehead skin
Describe the path of the nasociliary nerve after entering the orbit
Enters within common tendinous ring. Gives off several branches involved in sympathetic and parasympathetic eye responses, sensory to ethmoidal cells, eye, skin on nose
What is the main factor resulting in risk of infection spreading from the facial veins to cavernous sinus
The direction of the blood flow, not the absence of valves. There are valves.
What condition may occur with infection in the danger triangle
Cavernous sinus thrombosis. Formation of blood clot in the cavernous sinus
31 y/o male not able to close his right eye and not able to whistle
Obicularis occuli affected. Damage to facial nerve, exits the skull at stylomastoid foramen can be damged in skin cancer removal around tempals.
31 y/o male not able to close his right eye and not able to whistle
Obicularis occuli affected. Damage to facial nerve, exits the skull at stylomastoid foramen can be damged in skin cancer removal around tempals.
Cat with partial ptosis
Sympathetic chain damage, superior tarsal muscle effected.
64 y/o male presented to ED with no headache or neurological signs. Ct showed swelling of a muscle and has complete ptosis.
Damage to levator palpabrae muscle. Innervated by occulomotor.
A patient who suffers hyperhidrosis. What are possible side effects of sympathetic chain dissection?
Horners syndrome. Characterised by partial ptosis, meiosis, anhidrosis.
What bony structures form the orbit
Palatine bone, frontal bone, zygomatic bone, sphenoid bone, lacrimal bone, ethmoid bone, maxilla
Major bony structures that form the roof of the orbit
Frontal bone
Major bony structures of medial wall
Maxilla, lacrimal bone, ethmoid bone
Name layers of the eyelid
Skin, subcutaneous tissue (fatty), orbicularis occuli, septum, tarsus, conjunctiva
Two parts of obicularis oculi
Orbital and palpebral
What is the innervation of superior tarsal
Sympathetic, partial ptosis
What is innervation of levator palpebrae
Occulomotor, complete ptosis
What is Horners syndrome made up of and what is it caused by
Damage to the sympathetic chain. Partial ptosis, anyhydrosis, miosis.
What do the tarsus glands secrete
Oily substance
What is a stye or hordeolum caused by
Blocked sweat glands at base of eyelashes/ cellulitus
What is a chalazion from
Blocked tarsal glands (not painful)
Contents of orbital cavity
Eyeball, extrinsic muscles of the eyeball, lacrimal gland, neurovascular structures
What muscles are enclosed in the tendinous ring
The rectus muscles
What neurovascular structures are in the tendinous ring
Optic nerve, opthalmic artery, occulomotor, abducent and nasocilliary
If there is an infection in the periorbital layer which nerve/ artery are affected
All those in tendinous ring. Optic nerve, opthalmic artery, occulomotor, abducent and nasociliary
Most important branch of the opthalmic artery
Central retinal artery
What is the relevance of the danger triangle
Facial veins drain to opthalmic veins, to cavernous sinus, facial infection can lead to cavernous sinus thrombosis
Describe the course of superior oblique muscle
Origin outside of tendinous ring (medial to it), runs medially to sling located on lateral side of ethmoid bone and then anterior belly attaches to superior eyeball
Are there valves in opthalmic veins
Yes
