Anatomy of the Orbit Flashcards
How many bones make up the orbit of the eye?
7
Which bones make up the orbit of the eye?
- Frontal
- Zygomatic
- Maxilla
- Nasal
- Sphenoid
- Ethmoid
- Lacrimal
Which aspect of the frontal bone allows passage of the supraorbital nerve?
Supraorbital notch
Which bone contains the optic canal?
Sphenoid bone
The optic canal is the _____ of the bony orbit
The optic canal is the apex of the bony orbit
What is the main function of the optic rim?
Protects the eye from direct trauma
Which bones mainly comprise the following regions of the bony orbit?
a) Roof
b) Medial wall
c) Lateral wall
d) Floor
a) Roof - Frontal bone
b) Medial wall - Ethmoid bone
c) Lateral wall - Sphenoid bone
d) Floor - Maxilla
Which aspects of the bony orbit are particuarly weak and thin?
- Medial wall (ethmoid)
- Orbital floor (maxilla)
Which type of fractures are the medial wall and floor of the orbit particuarly susceptible to?
Blowout fractures
Which main problems arise with an orbital blowout fracture?
- Trapped orbital contents
- Infraorbital NVB damage
- Sensory deficit of facial skin
Which areas does the infraorbital nerve innervate?
- Ala of nose
- Skin around maxilla (lower eyelid to upper lip)
Why may a fractured zygoma result in double vision?
- Fractured zygoma rotates medially
- Suspensory ligament attaches to zygoma laterally
- Eye lowered to orbital floor as tension reduced
- Diplopia occurs
What is the name given to the muscle surrounding the orbit of the eye?
Orbicularis oculi
The orbicularis oculi is split into which two parts?
- Orbital part
- Palpebral part
Which type of secretion do the tarsal (eyelid) glands secrete?
Lipid secretion
What is the orbital septum and what is its function?
Sheet of fascia
Aids in preventing spread of infection
What is the name of the muscle(s) which elevates the upper eyelid?
- Levator palpebrae superioris
- Superior tarsal (Müller’s*) muscle
*Do not confuse with orbitalis muscle (also known as Müller’s muscle)
Which muscle is primarily responsible for:
a) Gently closing eyes
b) Screwing up eyes
a) Orbicularis oculi (palpebral aspect) - Gently closing eyes
b) Orbicularis oculi (orbital aspect) - Screwing up eyes
Which cranial nerve innervates the orbicularis oculi?
Facial nerve
(CN VII)
Which structure covers the iris?
Cornea
What is the limbus?
Corneal/scleral junction
Which glands are responsbile for tear production?
Lacrimal
Where does lacrimal fluid drain within the eye?
Puncta (inferior and superior)
What is the conjunctival fornix?
Loose arching folds connecting the conjunctival membrane lining the inside of the eyelid with the conjunctival membrane covering the eyeball
The conjunctiva does not cover which part of the eye?
Cornea
What is the pathway of lacrimal fluid drainage?
- Lacrimal puncta
- Canaliculi
- Lacrimal sac
- Nasolacrimal duct
- Nasal cavity
What is the approximate diameter of the eye?
25mm
What are the 3 main layers of the eye?
- Fbrous layer
- Vascular layer (uvea)
- Inner layer (retina)
The fibrous layer of the eye is comprised of which two main components?
- Sclera
- Cornea
The vascular layer (uvea) of the eye is comprised of which 3 parts?
- Iris
- Ciliary body
- Choroid
The inner layer of the eye (retina) is comprised of which 3 main parts?
- Macula
- Optic disc
- Retina
What is the anterior segment of the eye?
The part of the eye anterior to the lens