Anatomy-Orbit Flashcards
What structures are indicated below?
Optic canal, superior orbital fissure, and the inferior orbital fissure
What bones contribute to formation of the bony orbit of the skull?
Frontal (1), zygomatic (2), maxillary (3), lesser wing of sphenoid (4), greater wing of sphenoid (5), palatine bone (6), lacrimal bone (7), Orbital plate of ethmoid bone (8)
What structures is indicated below?
Periorbita fasciae (periosteum of the orbit)
What structure covers the muscles of the eye so that rotation of the eye remains smooth despite muscle attachments?
Bulbar sheath. This fuses with the muscular sheath as the muscles contact the eye.
What structures enter the orbit through annulus tendineus. What structures enter above & below it?
Below = inferior opthalmic vein. Above = superior opthalmic vein + lacrimal nerve (CN V) + frontal nerve (CN V) + Trochlear nerve (IV). Through = optic nerve, opthalmic artery, CN III, VI & nasociliary nerve (V1)
What innervates (motor) the superior oblique muscle?
Trochlear nerve.
What provides sensory innervation for the lacrimal region?
V1 (Opthalmic division)
What nerve is indicated below?
Frontal nerve (V1)
3 branches of trigeminal nerve in the orbit
Frontal, lacrimal & nasociliary
What nerve is responsible for corneal reflex? What other fibers run with it?
Nasociliary nerve (long ciliary branch). Post-ganglionic sympathetic innervation to the pupil also courses along this nerve.
What are the four branches of the nasociliary nerve?
1) Infratrochlear 2) Anterior ethmoidal 3) Posterior ethmoidal 4) Long Ciliary
What is the function of the structure indicated below?
That is the ciliary parasympathetic ganglion. Note how fibers course w/CN III to form the ganglion. These fibers innervate the sphincter pupillae (constricts pupil) and ciliary muscles (used to change lens shape)
What nerve provides motor innervation for abduction of the eyes?
Abducens nerve, innervating the lateral rectus muscles.
What innervates each structure indicated below?
1) Levator Palpebrae Superioris = CN III (superior division) 2) Superior Rectus = CN III (superior division) 3) Lateral rectus (CN VI) 4) Medial rectus = CN III (inferior division)
What are the adductors of the eye?
Medial rectus, superior rectus, inferior rectus
What innervates each structure shown below?
1) Inferior rectus = CN III (lower division) 2) Superior Oblique = CN IV 3) Inferior Oblique = CN IV
What muscles lower the eye?
Inferior rectus
What does superior oblique do?
Depression and abduction of the pupil
What does the inferior oblique do?
Elevation and abduction of the pupil
A patient presents with difficulty doing the movement shown below. What orbital muscle is he having trouble with?
Superior rectus
A patient presents with difficulty doing the movement shown below. What orbital muscle is he having trouble with?
Inferior oblique
A patient presents with difficulty doing the movement shown below. What orbital muscle is he having trouble with?
Inferior rectus
A patient presents with difficulty doing the movement shown below. What orbital muscle is he having trouble with?
Superior oblique
A patient presents with difficulty doing the movement shown below. What orbital muscle is he having trouble with?
Medial rectus
A patient presents with difficulty doing the movement shown below. What orbital muscle is he having trouble with?
Lateral rectus
How do you clinically test the muscles of the eye?
6 cardinal directions
A patient presents with a closed left eye. You lift up the eyelid and find that the eye is abducted and downward. The pupil is dilated and accommodation is absent. What is causing the patient to present this way?
CN III damage. Parasympathetics that run w/CN III were also damaged and cause a dilated pupil. Loss of innervation to the Levator Palpebrae Superioris causes true ptosis. Unopposed action by lateral rectus and superior oblique cause the eye to point down and out.
A patient presents with double vision and the physical exam shown below. When he looks right, eyes are normal. When he looks straight, esotropia appears. What is causing this?
CN VI injury causes paralysis of the left lateral rectus that manifests when the patient is looking forward. It is further exaggerated by having the patient look towards the left as seen below.
How do patients with CN VI damage overcome horizontal diplopia?
They fix the abnormal eye on the object. Then the good eye rotates to fixate on it.
A patient presents with oblique diplopia (images separated horizontally and vertically). Physical exam findings are shown below. What is causing this?
Injury to the trochlear nerve causes paralysis of the superior oblique muscle. The patient will not be able to push the affected eye (left in this case) downwards from the medial position.
How do patients with left CN IV palsy compensate so they can walk down stairs without falling?
They tilt their heads to the unaffected side, causing the normal eye to intort and align with the extorted eye.
Branches off the opthalmic artery
1) Posterior ethmoidal 2) Lacrimal 3) Long & Short Ciliary 4) Anterior Ethmoidal 5) Supratrochlear 6) Dorsal nasal 7) Medial Pelpebral 8) Supraorbital
Why can popping a zit possibly cause intracranial infection?
The superior and inferior opthalmic veins drain the face and move to the cavernous sinus, creating a pathway for possible spread of infection.
