Orbit 2 Flashcards
Name 2 sensory nerves to the eyeball
- Optic
2. Ophthalmic of trigeminal
Name 3 sensory nerves to the eyeball
- Oculomotor
- Trochlear
- Abducent
What are the 3 branches of the ophthalmic nerve?
- Frontal
- Lacrimal
- Nasociliary
What are the 2 terminal branches of the frontal nerve?
- Supratrochlear
2. Supraorbital
Where do the supratrochlear and supraorbital nerves innervate?
Sensory innervation for skin of forehead and scalp
Where does the lacrimal nerve innervate?
Lacrimal gland
Once innervating the lacrimal gland, what happens to the lacrimal nerve?
Pierces orbital septum and supplies the skin of lateral part of the eyelid
Where does the nasociliary nerve innervate?
Anterior nasal mucosa
Describe the path of the nasociliary nerve
- Gives off sensory branches
- Passes through anterior ethmoidal foramen
- Enters nasal cavity
What branch is given off the nasociliary nerve?
External nasal
Where does the external nasal nerve supply?
Skin of the nose
Where does the optic nerve enter the orbit?
Optic canal
What nerve accompanies the optic nerve in the optic canal?
Ophthalmic of trigeminal
What surrounds the optic nerve?
Meninges
Describe the course of the optic nerve within the optic canal
- Runs within the cone of recti muscles
2. Pierces sclera as a point medial to posterior pole of eyeball
What occurs when the optic nerve pierces the sclera?
The meninges and sclera fuse
What is the function of the optic nerve?
Transmits sensory information regarding brightness, red-green colour perception and visual field
What is papilledema?
Oedema of the optic disc
What is papilledema a sign of?
Elevated intracranial pressure
List 3 things which can cause papilledema
- Brain tumour
- Cerebral haemorrhage
- Cavernous sinus thrombosis
What are 2 symptoms of papilledema?
- Blurred vision
2. Double vision
Where does the oculomotor nerve leave the brainstem?
Between the midbrain and pons
How do the superior and inferior branches of the oculomotor nerve enter the orbit?
Superior orbital fissure
What 2 muscles does the superior ramus of the oculomotor nerve supply?
- Superior rectus
2. Levator palpebrae superioris
What 3 muscles does the superior ramus of the oculomotor nerve supply?
- Inferior rectus
- Medial rectus
- Inferior oblique
What is the function of the branch from the nerve to inferior oblique?
Carries parasympathetic fibres to sphincter pupillae and ciliary body
How does the trochlear nerve enter the orbit?
Superior orbital fissure above common tendinous ring
Where does the abducent nerve leave the brainstem?
Junction of pons and medulla
Describe the course of the abducent nerve after leaving the brainstem
- Enters cavernous sinus
- Reaches orbit through superior orbital fissure within common tendinous ring
- Passes laterally to supply lateral rectus
What does paralysis of the abducent nerve cause?
Medial squint
What does paralysis of the oculomotor nerve cause?
Lateral squint
What does trochlear nerve palsy cause?
Double vision
Why does trochlear nerve palsy cause double vision?
The weakened muscle prevents the eyes from moving in the same direction together
Where does the ophthalmic artery originate?
Internal carotid artery
Describe the course of the ophthalmic artery
- Passes beneath optic nerve
- Accompanies optic nerve through optic canal
- Curves over optic nerve from lateral to medial
What are the 5 branches of the ophthalmic artery?
- Central retinal artery
- Lacrimal artery
- Ciliary arteries
- Supraorbital artery
- Supratrochlear artery
Where does the lacrimal artery supply?
Lacrimal gland
What are the 4 components of the lacrimal apparatus?
- Lacrimal gland
- Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
What is the function of the lacrimal apparatus?
Tear production and drainage
What are 2 functions of the lacrimal gland?
- Secrete tears
2. Contains excretory ducts to convey fluid to surface of the eye
What is the function of the nasolacrimal duct?
Conveys fluid to the nose, emptying in the inferior nasal conchae
What is the function of blinking?
Moves tears from lacrimal gland to sac to keep eyeball moist
What can occur if the eyeball dries out?
Corneal ulcers may form
What are the 2 major veins of the orbit?
- Superior ophthalmic vein
2. Inferior ophthalmic vein
What are the 2 communications of the ophthalmic veins?
- Cavernous sinus
2. Pterygoid venous plexus
How do the ophthalmic veins communicate with the cavernous sinus?
Via superior orbital fissure
How do the ophthalmic veins communicate with the pterygoid venous plexus?
Via inferior orbital fissure
How is the superior ophthalmic vein formed?
Unification of supraorbital and supratrochlear veins
What communication does the superior ophthalmic vein form?
Skin of the face and cavernous sinus
Name 3 intrinsic muscles of the eye
- Ciliary muscle
- Constrictor pupillae
- Dilator pupillae
What is the function of the ciliary muscle?
Accommodation of the lens
Describe the innervation of the ciliary muscle
Parasympathetic innervation by the oculomotor nerve
What is the function of the constrictor pupillae?
Constriction of the pupil
Describe the innervation of the constrictor pupillae
Parasympathetic innervation by the oculomotor nerve
What is the function of the dilator pupillae?
Dilation of the pupil
Describe the innervation of the dilator pupillae
Parasympathetic innervation by the superior cervical ganglion
