Eyelids and Conjunctiva - Week 2 Flashcards
Functions of eyelids (palpebrae) [4]
- protect eyeball from injury
- —– (via lashes, cilia, via sensory, spontaneous + reflex blinking)
- maintain position of globe in orbit (without restriction of ocular rotational movement)
- maintenance of corneal surface integrity (tear distribution and drainage)
- gross regulation of incident light levels (aperture size/lashes)
** Way to remember
PAPI - Protect, Aperture, Position, (surface) Integrity
How many basic regions does an eyelid/palpebrae have (on surface anatomy)
2 regions: orbital and palpebral (tarsal)
How many sulcii are present on the eyelids (surface anatomy, in total)? What are they?
4 sulcii
- superior palpebral sulcus (top eyelid fold)
- Inferior palpebral sulcus (bottom eyelid fold)
- Malar (lateral) sulcus
- Nasojugal (medial) sulcus
In what common scenario does the inferior palpebral sulcus become more pronounced?
When you lack sleep
In respect to the eyelid margin, what are cilia?
hair. Therefore eyelashes
How many cilia make up the upper and lower eyelashes?
150 upper, 70 lower
How frequently are cilia/eyelashes replaced?
replaced every 3-5 months
What do Meibomium glands look like?
little dots lying on the eyelid margin (they are openings)
What is the Orbicularis Oculi?
is a muscle in the face that closes the eyelids.
– i.e. It is a sphincter muscle for palpebral fissure
Define ‘Palpebral Fissure’
The palpebral fissure is the elliptic space between the medial and lateral canthi of the two open lids. In simple terms, it refers to the opening between the eye lids
What type of muscle is the Orbicularis Oculi?
Striated Muscle
What are the 2 parts of the Orbicularis oculi muscle? And what are these parts involved with?
Orbital part: forceable lid closure
palpebral part: gentle blinking and sleep
What is the Orbital Septum?
Is the connective tissue sheath that forms the anterior border of the orbit
What are the functions of the Orbital Septum?
- separates eyelids from contents of the orbital cavity
- is an almost continuous barrier preventing the anterior-posterior spread of inflammation or blood
In terms of location, where do the following blend with:
A) Superior Eyelid
B) Inferior Eyelid
Superior eyelid - blends with tendon of Levator palpebrae superiosis (LPS) and superior tarsus
Inferior eyelid - blends with inferior tarsus
What muscles are involved in eyelid control? (3)
- Orbicularis Oculi - forceable lid closure and blinking and sleep; closes lids
- Levator Palpebrae - elevates upper lid and maintains open palpebral aperture
- Muller’s Muscle - modulates lid position when eye is open
*OML - Oh My Lid!
What type of muscle is levator palpebrae superioris?
Striated
Fill in the blank: Levator palpebrae superioris (LPS) is innervated by ____?
Superior branch CNIII (cranial nerve 3)
Where does LPS originate from? Where does it go from there?
Arises in region of annulus of Zinn, moves forward on top of SR muscle
Where does LPS insert?
LPS inserts into the skin of the superior eyelid (passing through the orbicularis)
What does LPS give rise to?
Muller’s Muscle
True or False: Muller’s muscles are striated
False. Muller’s muscles are a layer of NON-striated muscle fibres
Where are Muller’s muscles located?
Muller’s Muscles are located just behind the orbital septum
Which is larger? The superior palpebral muscle of muller or the inferior palpebral muscle of muller
superior is larger
where do muller’s muscles attach?
attached to margins of tarsal plate
What system innervates the muller’s muscles?
Sympathetic nervous system
For which diseases or drugs do muller’s muscles hold clinical significance?
- Horner’s syndrome
- Topical alpha agonists
What portion of the orbicularis is involved with Meibomium secretion?
The ciliary portion