Orbit 1 Flashcards
What bones make up the outer rim of the orbit?
Frontal, zygomatic, maxilla
Spatial: frontal bone
superior rim of orbit, also forms roof of orbit
Spatial: zygomatic bone
lateral rim of orbit
Spatial: maxilla
medial and inferior rim of orbit, also forms a large part of the floor of the orbit
What bones form the inside of the orbit?
Lacrimal, ethmoid, sphenoid, and palatine
Spatial: lacriminal bone
located on the anterior aspect of the medial wall. The fossa (which is for the lacriminal sac) and is surrounded by anterior (maxilla) and posterior (lacriminal bone) lacriminal crests
Spatial: ethmoid bone
Makes up majority of the medial wall.
What is the lamina papyracea?
the very thin portion of the bone which separates the orbit from the ethmoidal air cells
Spatial: sphenoid bone
- Lesser (optic canal) and greater wings make up large portion of posterior aspect of orbit
- Superior orbital fissure lies between the lesser and greater wings
- The inferior orbital fissure lies between the greater wing and the maxilla.
- The inferior and superior orbital fissures meet one another medially
Spatial: Palatine bone
The orbital process helps form a small portion of the posterior floor of the orbit between the inferior orbital fissure and the maxilla
What is the base of the orbit?
Orbital margin
How is the base of the orbit protected?
The orbital margin is reinforced
What is the apex of the orbit?
The optic canal
Spatial: Optic canal (from orbit view)
Medial to the superior orbital fissure
What is the superior wall/roof of the orbit?
Frontal bone and lesser wing of the sphenoid near the apex
What is the medial wall of the orbit?
Ethnoid and lacriminal bones, with small contributions from the frontal, maxillary, and sphenoid bones.
What orbital walls are fragile?
Inferior wall (most fragile) and the medial wall
What is the inferior wall of the orbit?
Primarily maxilla, with contributions from the zygomatic and palatine bones.
What is a blowout fracture?
During a sharp blow to the eye, the floor fractures causing the eye to partially fall into the sinus below
What is the lateral wall of the orbit?
Primarily zygomatic and sphenoid bones, with small contributions from the frontal bone
What is the strongest wall of the orbit?
The lateral bone
What structures protect and aid in the lubrication of the eye?
The superior and inferior palpebrae
What is the skin continuous with?
The palebral conjunctiva
Where does the skin meet the palpebral conjunctiva?
the mucocutaneous junction
What is the mucus membrane on the inside of the eyelid?
palebral conjunctiva
What is the palebral conjunctiva continuous with?
the skin and the orbital (bulbar) conjunctiva
What is the eyes protective covering?
The orbital (bulbar) conjunctiva)
What is the space between the upper and lower lids?
Palebral fissure
Spatial: palebral margins
surround the palebral fissure, meet at the canthi (angles)
What is the order of the eyelid layers?
- skin 2. subcutaneous connective tissue 3. Muscular layer 4. Submuscular layer 5. Tarsal plate 6. Tarsal glands 7. Palpebral conjunctiva
What causes Horner’s syndrome?
Lesion to the superior cervical sympathetic ganglion
What are the symptoms of Horner’s syndrome?
paralysis in the Tarsal muscle on the affected side
1) ptosis (drooping eyelid)
2) Meiosis (small pupil)
Anhydrosis (lack of sweating) and reddening of the skin on the affect side
What is the large medial angle of the eye?
The lacrimal lake
What is the lacrimal caruncle?
The fleshy elevation seen in the medial angle of the eye, within the lacrimal lake
What does the lacrimal caruncle contain?
sweat glands, sebaceous glands, and cilia
Spatial: Plica semilunaris
Lateral to the lacriminal caruncle
What is the plica semilunaris?
The connective tissue band that seperates the sclera from the lacriminal lake
Spatial: Lacrimal gland
superolateral aspect of the orbit
Where do the ducts of the lacrimal gland drain?
Into the superior palpebral fornix
Spatial: palpebral fornix
the junction of the palpebral and orbital conjunctiva
What cells are in the lacriminal gland?
Serous only cells that secrete a watery solution that contains the bacteriocidal enzyme lysozyme, which provides nurtirents and dissolved oxegyn to the cornea
What are the two portions of the lacriminal gland?
The palebral protion and the orbital portion
Where do tears collect?
In the superior fornix of the upper lid, and pass over the eye surface, aided by blinking
What is the drainage system called?
The lacrminal apparatus
How do tears drain?
They flow from the superlaterally placed lacriminal gland inferomedially to the medial canthus of the eye, where they drain:
Punctua lacrimali: drain opening
Lacrminal canaliculus: duct
Lacriminal sac: collection of fluid
Nasolacriminal duct: drainage to nasal sinus
Are the motor fibers to the lacrimal gland parasympathetic or sympathetic in nature?
parasympathetic
What cranial nerve is associated with the lacriminal gland?
CN VII, through the greater petrosal nerve
What is the nerve of the pterygoid canal?
the greater petrosal nerve + the deep petrosal nerve, which courses into the ptergopalatine fossa to the pterygopalatine ganglion where only the parasympathetic fibers synapse
What does sympathetic stimulation of the lacriminal gland result in?
vasoconstriction and a subsequent decrease in tear production
What makes a muscle a recti muscle?
It originates from the annulus tendineus
What is the annulus tendineus?
a fibrous ring which encircles the junction of the super and inferior orbital fissures and the optic canal
What are the recti muscles?
Superior rectus, inferior
What are the extraocular muscles?
superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique (sphenoid), inferior oblique (maxilla), levator palpebrae superioris (sphenoid)
What direction do the eye muscles pull?
Inferior oblique: up and out
Superior oblique: down and out
Superior recti muscles: medial
Inferior recti muscles: medial
What nerves innervate the extraocular muscles?
oculomotor, trochlear, abducent
What is the role of the oculomotor nerve?
The superior division innervates the levator palpebrae superioris muscle and the superior rectus. The inferior division innervates the medial and inferior rectus muscles as well as the inferior oblique muscle. The nerve also carries parasympathetic fibers to the ciliary ganglion
What is the role of the trochlear nerve?
It innervates the superior oblique muscle (which passes through the trochlea)
What is the role of the abducent nerve?
It innervates the lateral rectus muscle (which abducts the eye)
How do the three oculomotor nerves enter the orbit?
Through the superior orbital fissure
How does the optic nerve enter the orbit?
via the optic canal, with the ophthalmic artery
What is the largest nerve in the orbit?
Optic nerve
What supplies sensory innervation to the orbit and external eye?
the ophthalmic division of the trigeminal nerve
Spatial: lacriminal nerve
Part of the opthalmic division of the trigeminal nerve. Runs along the superior and lateral aspect of the orbit to supply sensory innervation to the lacrimal gland and the lateral aspect of the eye and the upper and lower palpebrae. Postganglionic parasympathetics join this nerve after running with the zygomaticotemporal branch of V2
Spatial: frontal nerve
Part of the ophthalmic division of the trigeminal nerve. Runs along the roof of the orbit superior to the levator papebrae superioris muscle. Divides into medial supratrochlear nerve and lateral supraorbital nerve.
Role: supertrochlear nerve
sensory innervation to the skin above the medial canthus and a portion of the scalp
Role: supraorbital nerve
supplies the superior palpebral and the scalp above
Spatial: nasociliary nerve
crosses above the optic nerve from lateral to medial, and gives off following branches:
1) communicating branch to the ciliary ganglion
2) long ciliary nerves
3) posterior ethmoidal nerve
4) anterior ethmoidal nerve
5) infratrochlear nerve
Spatial: Ciliary ganglion
located between the optic nerve and the lateral rectus muscle
What fibers synapse in the ciliary ganglion?
parasympathetic fibers from CNIII
What fibers enter the ciliary ganglion?
sensory, sympathetic, and parasympathetic
Where do parasympathetic fibers of oculomotor nerve originate from?
edinger-westphal nucleus of oculomotor nerve
What do the parasympathetic fibers of CNIII do?
cause constriction of the pupil (sphincter pupillae m) and allow the eye to focus on near objects (contraction of the ciliary muscle)
What nerves are in the orbit?
optic nerve, oculomotor, trochlear, trigeminal (1), adbducent, sympathetics, parasympathetics
What are the branches of the optic artery?
meningeal branches, lacrimal, central retina, long and short ciliary, supraorbital, anterior ethmoidal, posterior ethmoidal, supratrochlear, medial and lateral palpebral, dorsal nasal
Describe the venous drainage of the orbit
drains throught he superior and inferior ophthalmic veins, which pass through the superior orbital fissure and enter the cavernous sinus
