Orbit and Eye Screencast Flashcards
What are the six bones that make up the orbit?
Frontal, zygomatic, sphenoid, ethmoid, lacrimal, maxilla
What bones have orbital plates?
Frontal, ethmoid and maxillary = smoother and flatter areas of bone
Why are the maxillary and ethmoid orbital plates likely to fracture?
The bone is thin
What structures pass through the optic canal?
The optic nerve and ophthalmic artery
What passes through the supraorbital notch?
The supraorbital neurovascular bundle
What division does the supraorbital nerve belong to?
CN V1
What passes through infraorbital foramen?
Infraorbital neurovascular bundle
What division does the infraorbital nerve belong to?
CN V2
What shape is the orbit?
Pyramidal = faces anteriorly (has different axis from eyeball)
What is the base of the orbit called?
The orbital rim
What makes up the apex of the orbit?
The sphenoid bone
What is the benefit of the supraorbital margin overhanging the infraorbital margin?
It protects the eye (bones of this area is also thick)
What occurs in a blowout fracture?
The thicker bones stay intact but the thinner bones fracture = medial wall and orbital floor are common sites
What occurs in a trapdoor fracture?
Soft tissue structures pass through the fractures
Where do the bones on the outside of the orbit tend to fracture?
At sutures
What makes up the most superficial layer of the eyelid?
The orbicularis oculi = has orbital and palpebral parts
What is the orbital part of the orbicularis oculi?
Area around the entire outside of the orbit = carries out tight closure of eye
What is the palpebral part of the orbicularis oculi?
Covers the actual eyelid = carries out gentle closure of eye
What nerve innervates the orbicularis oculi?
CN VII
What makes up the deep layer of the eyelid?
Superior and inferior tarsus, tendon of LPS, lateral and medial palpebral ligaments, orbital septum
What are the inferior and superior tarsus?
Fibrous skeleton = thickened bands of connective tissue
Where are the lateral and medial palpebral ligaments located?
On either side of the tarsus
What is the function of the orbital septum?
Prevents spread of infection from superficial to deep and holds orbital contents in place
What is the orbital septum made of?
Tough connective tissue
What is the action of the levator palpebrae superioris?
Lifts upper part of the eye
What is the superior tarsus muscle?
Slip of smooth muscle that comes off of the levator palpebrae superioris = also called Mueller’s muscle
What does the superior tarsus muscle do?
Helps widen the eye = under sympathetic control
Where are the tarsus glands located?
Within the tarsus = Meibomian glands
What do the tarsus glands secrete?
Secrete lipids = cover bottom of eyelids to prevent lacrimal overflow
What do the lacrimal glands produce?
Lacrimal fluid (tears)
What is the flow of lacrimal fluid?
Wash over eye, pushed towards medial angle by blinking, drains through lacrimal puncta, eventually reaches inferior meatus
Where is the lacrimal gland located?
In the lacrimal fossa
What innervates the lacrimal glands?
Parasympathetic innervation from CN VII
Where do tears collect?
Collect in lacrimal lake = then pass through puncta into canaliculi
What is the first part of the nasolacrimal duct?
Lacrimal sac
How many extra-ocular muscles are there?
7 = 4 rectus muscles, 2 oblique muscles and the levator palpebrae superioris
Where do the rectus muscles pass?
Run from orbit straight onto the eyeball
What are the rectus muscles?
Superior and inferior, medial and lateral
What are the oblique muscles?
Superior and inferior = insert onto eyeball at oblique angle and attach more posterior than rectus muscles
What does the superior oblique muscle pass through?
The trochlea = loop of connective tissue which acts as a pulley to turn the muscle
Where do the rectus muscles originate from?
Common tendinous ring (annulus) = anterior to optic canal
Where do the rectus muscles insert on to?
The sclera
Where does the superior oblique muscle originate from?
The sphenoid bone
Where does the inferior oblique originate from?
Orbital plate of maxilla
Where does the levator palpebrae superioris originate from and insert onto?
Origin = lesser wing of sphenoid Insertion = skin and superior tarsus
What nerve innervates the lateral rectus muscle?
CN VI
What muscle does CN IV innervate?
Superior oblique muscle
What muscles does CN III innervate?
Inferior oblique, superior and inferior rectus, medial rectus, levator palpebrae superioris
