BS - Eyelids and Conjunctiva - Week 2 Flashcards
Name the 4 functions of the eyelids.
Protection of the eyeball from trauma
Maintains the position of the globe within the orbit
Maintains integrity of the corneal surface
Regulation of incident light levels
Define the inner and outer canthus (canthi).
Inner - found nasally, where the eyelids meet.
Outer - found temporally, where the eyelids meet.
Define the tarsal and palpebral portions of the eyelid.
Tarsal - marginal area of the eyelid
Palpebral - area of the eyelid closer to the zygoma/frontal bone.
Where is the lacrimal caruncle found?
At the inner canthus.
Where can the plica semilunaris found, and what is it?
A membranous sheath that acts as a thirs eyelid in some species, but is vestigial in humans. It can be found just lateral to the inner canthus.
Where is the nasojugal sulcus found?
Inferior and medial to the palpebral sulcus, found along the margin bordering the nose.
Where is the malar sulcus found?
Found at the level of the nasojugal sulcus, but temporally, somewhat in line with the outer canthus.
Where is the inferior palpebral sulcus found?
Found just inferior to the inferior eyelid.
Where is the superior palpebral sulcus found? What two regions does it separate?
Found just superior to the superior eyelid margin. It separates the tarsal and palpebral regions of the superior eyelid.
What 3 structures are found at the eyelid margin?
Cilia (eyelashes)
Meibomian glands
Rich neural supply
What is the main muscle of the eyelids, and what kind of muscle is it? Define its 4 regions, and where they can be found.
Orbicularis oculi, a striated muscle.
It has 2 main regions, palpebral - found on the eyelids, and orbital, found on the palpebral margin.
Palpebral portion has 3 regions:
Pretarsal - found directly over the tarsal eyelids
Preseptal - found bordering the pretarsal region
Ciliary - found within the pretarsal region
The orbital region is found surrounding the palpebral region. The lacrimal region is found behind the lacrimal sac.
Aside from the orbicularis oculi, name 3 additional muscles of the eyelid in the region, and where they are.
Occipitofrontais - Extends from the superior border of the orbicularis oculi, towards the frontal bone.
Procerus - found medially, arising at the medial top margin of the nose, and extends superiorly towards the frontal bone.
Corrugator - A muscle found inferiorly between the margins of the orbicularis oculi and the procerus, responsible for eyebrow contraction.
What is the anterior boundary of the orbit, and what two regions does it separate?
The orbital septum, also palpebral fascia. It separates the eyelids from the orbital cavity.
Describe the barrier formed by the palpebral fascia/orbital septum, and what it prevents.
It forms an almost continuous barrier and prevents an anterior-posterior spread of inflammation or blood.
What does the palpebral fascia blend with at the superior and inferior eyelid?
Superior - it blends with the tendon of levator palpebrae superioris, and the superior tarsus.
Inferior - it blends with the inferior tarsus.
What is the main action of the levator palpebrae superioris, and what kind of muscle is it?
A striated muscle responsible for eyelid elevation during blinking.
Which nerve innervates the levator palpebrae superioris muscle?
CNIII, superior branch
Where does the levator palpebrae superioris muscle originate from, and which muscle does it overlie?
Arises from the region of the annulus of Zinn, and moves forward on top of the superior rectus muscle.
Where does the levator palpebrae superioris muscle insert into, and what muscle does it pass through?
Inserts into the skin of the superior eyelid, passing through the orbicularis oculi.
What muscle does the levator palpebrae superioris give rise to in the superior eyelid, and what structure does this allow the levator to contact?
How are these two muscles clinically significant?
The levator palpebrae superioris gives rise to Mullers muscle, through which it contacts the top of the tarsal plate.
These two are clinically relevant in Horner’s syndrome.
From what muscle is Mullers muscle derived from in the inferior eyelid?
The inferior rectus muscle.
Where does Mullers muscle attach to?
The margins of the tarsal plate
What system innervates Mullers muscle (symp/parasymp)?
Sympathetic.
What kind of muscle is Mullers muscle?
Non-striated
Where can Mullers muscle be found in relation to the orbital septum?
Just deep to it.
Name the function for each of the 2 general regions of the orbicularis oculi muscle.
Orbital - forced lid closure
Palpebral - gentle blinking and sleep
Collectively they close the eyelids.
Name the function of the levator palpebrae superioris.
Elevates the upper eyelid.
Name the 3 functions of Mullers muscle.
Modulates the lid position when eyelids are open
Raises the eyelids in fight or flight response
Paralysis - partial ptosis
Name 3 problems that can occur with the muscles of the eylids, and what symptom they cause if applicable.
Ptosis (entropian/ectopian)
Paralysis of orbivularis oculi
-prevents eyelid closure
Paralysis of levator palpebrae superioris
-drooping lid or ptosis
Name 4 eyelid abnormalities.
- Meibomian gland dysfunction (lipid dry eye)
- Internal hordeolum (meibomian infection)
- External hordeolum (Zeiss or Moll infection)
- Chalazion (inflammatory, non-infective blockage of meibomian)
What four eyelid muscles are innervated by the facial VII nerve, and which branch?
Orbicularis oculi
- Upper - temporal and superior zygomatic branch
- Lower - lower zygomatic branch
Frontalis - temporal branch
Procerus - temporal branch
Corrugator - superior zygomatic branch
What are the smallest and largest nerves of the ophthalmic division of the trigeminal V nerve?
Lacrimal - smallest
Frontal - largest
What is the main nerve providing sensory innervation to the superior eyelid? Give an additional 3. Breifly mention which region of the eyelid they innervate.
Supraorbital nerve of the ophthalmic trigeminal V nerve. Innervates majority of the superior eyelid Also supratrochlear (innervates superior medial), infratrochlear (innervates inferior medial), and lacrimal nerves (innervates laterally) - all 3 are D1 of CNV.
What is the main nerve providing sensory innervation to the inferior eyelid?
Infraorbital nerve, from the maxillary division of trigeminal V nerve.
Which main artery is the ocular blood supply drerived from? Where is this artery also derived from?
Mainly supplied by the ophthalmic artery, which is derived from the internal carotic artery.
Name the 6 main branches of the ophthalmic artery that supplies blood to the ocular region.
Central retinal Muscular Lacrimal Short posterior ciliary Long posterior ciliary Anterior ciliary
Which artery supplying the eyelids and adnexa is not derived from the ophthalmic artery? Name its derivative.
Infraorbital, which derives from the maxillary artery.
