Eyelid Structure Flashcards
The upper eyelids extend from the ___ to the ____.
Conjunctival fornix to the superior orbital rim/margin.
Lower eyelids extend from the ____ to the ___
Conjunctival fornix to the nasojugal crease (nose/relating to the zygoma AKA bony arch of the cheek) and palpebromalar sulci.
Upper and lower eyelids meet where?
At the canthus, which is where the eyelids physically touch.
Opening between the upper and lower eyelids
Palpebral fissure (can be horizontal, or vertical)
Difference between canthus and palpebral fissure
Canthus- Where the physical eyelids touch
Palpebral fissure is the space between the eyelids
Lateral canthus
is 5-7 mm medial to the lateral orbital rim and lies directly on the globe.
Medial canthus
Is at the medial orbital rim and is separated from the globe by the lacrimal lake.
Difference between the medial and lateral canthus
Lateral canthus sits directly on the globe and the medial canthus does not. It it separated from the globe by the lacrimal lake.
What is the average distance between the horizontal and vertical palpebral fissure
Horizontal fissure is typically 30mm. (distance from lateral to medial)
Vertical fissure is typically 10 mm. (distance superior to inferior)
These numbers could differ if there is an eyelid droop.
MRD- 1 and MRD-2
Marginal reflex distance- 1 is the distance between the corneal reflex and the upper lid margin (4-4.5mm is normal)
Marginal reflex distance- 2 is the distance between the corneal reflex and the lower lid margin (Greater than 5mm is normal)
MRD1 + MRD2 =
vertical palpebral fissure.
Fornix
Part of the conjunctiva. Where the upper and lower lids originate.
Why is skin of the eyelid different from the rest of the body
The skin of the eyelid is thinner, has little to no fat, has a very thin dermis and has less sebaceous glands and sweat glands.
Function of the skin of the eyelid
Functions as a barrier to the outside environment, prevents microbes from causing infections in underlying tissue.
Characteristics of the eyelid
Folds easily, very flexible, thinnest skin in the body
Why is it important for the eyelid to fold easily and flexibly
Important for rapid movements during blinking
How thin is the skin of the eyelid and why is it so thin?
Less than 1 mm in thickness. It is so thin because of attenuated (thin) dermis and minimal hypodermic tissue (since there is such low fat in the eyelid and fat usually makes up the majority of the hypodermis).
characteristics of the dermis in the eyelid
Attenuated in the eyelid
Has less adnexal structures (hair follicles, hair, sebaceous glands and sweat glands).
Where in the eyelid is the hypodermis absent
The tarsal region of the eyelid.
During eyelid reconstruction, the ideal skin choice is what?
Contralateral eyelid skin. Contra= other, Lateral= side.
What kind of tissue is the tarsal plate/tarsus composed of?
Dense connective tissue, which gives the lids structure and rigidity.
How thick is the tarsal plate/tarsus?
1-1.5 mm thick
How far does the tarsal plate horizontally extend
about 30mm
Central vertical height for superior and inferior tarsus
9-11 mm for superior tarsus and 4-5mm for inferior tarsus.
Superior tarsus extends from the eyelid margin to the ____
Superior palpebral sulcus
The inferior tarsus extends from the eyelid margin to the ___
Inferior palpebral sulcus
What shape is the tarsus
Curved to the contour of the anterior globe.
Laterally, what is the tarsus connected to
The medial and lateral palpebral ligaments (AKA Canthal tendons)
The upper edge of the superior tarsus is attached to the
Levator aponeurosis and muller’s muscle
The lower edge of the inferior tarsus is attached to the
Capsulopalpebral fascia and muller’s muscle
Within each tarsal plates are the
Meibomian glands that extend the vertical length of the tarsal plate.
Are there more meibomian glands in the upper or lower lids
Upper
Meibomian glands are just modified
Sebaceous glands
What do meibomian glands secrete
Oil that is apart of the tear film. Forms the sebaceous glands within the tarsal plate.
The orbital septum extends the entire ___ to the ___
Extends the entire rim of the orbit to the tarsal plate.
In the upper lid, the orbital septum becomes a thickening of the ___ at the ____
Thickening of the periosteum at the superior orbital rim. Distal fibers merge with the levator aponeurosis 3-5 mm above the tarsal plate.
In the lower lid, the orbital septum becomes a thickening of the ___ at the ___
Periosteum at the inferior orbital rim. Distal fibers merge with the capsulopalpebral fascia several mm below the tarsal plate.
What skeletal muscle functions as the protractor of the upper and lower eye lids?
Orbicularis Oculi
How does the orbicularis oculi close the eyelid?
It contacts to extend/lengthen the eyelid AKA closing the eye.
Origination and insertion of he orbicularis oculi muscle
Origination at the medial orbital rim at the maxillary and lacrimal bones. It encircles the eye and inserts into the lateral palpebral ligament (lateral canthal tendon)
What two regions is the orbicularis oculi muscle divided into
- Orbital region. Concentric fibers that extend from the orbital rim to the forehead, temple, and cheek.
- Palpebral region. Superior and inferior semilunar fibers extend from the lateral palpebral ligament (lateral cantonal tendon) across the eyelid to the medial palpebral ligament (medial canthal tendon)
What region of the orbicularis oculi muscle is responsible for closing the eye gently? (winking, blinking) What about closing it tightly shut?
The palpebral region closes the eye gently.
The orbital region extends higher up into the brow and is responsible for squeezing eyes shut. Will also produce wrinkles on forehead.
Two divisions of the palpebral region of the orbicularis occuli
The palpebral region is the area that covers the eyelid. There are two divisions-
- Preseptal, which is anterior to the orbital septum.
- Pretarsal, which is anterior to the tarsal plates.
Where are riolan’s muscle and horner’s muscle found?
The pretarsal area of the palpebral region of the orbicularis oculi muscle.
Riolan’s muscle
Fibers near the lid margin. Apart of the pre-tarsal region of the palpebral region of the orbicularis oculi muscle.
Function to maintain the lid margin close to the globe. This prevents dry eye.
Horner’s muscle
Medial fibers apart of the pre-tarsal region of the palpebral region of the orbicularis oculi muscle.
Aids in lacrimal pump mechanism. Pumps tears down the nasolacrimal drainage system.
With age, tears aren’t pumped out of the eye as efficiently and may run down the pt’s face. Why is that?
Horner’s muscle, which aids in the lacrimal pump mechanism, atrophy with age. This decreases drainage efficiency.
What is the antagonist muscle of the orbicularis oculi?
The levator and frontalis muscles.
The frontalis and Levator muscles must do what in order for the ____ to close the eye?
The frontalis and Levator muscles must RELAX in order for the orbicularis oculi to contract and close the eye. They are antagonists of each other since the frontalis wants to raise eyebrows and the Levator contracts to open eyes.
If the eye looks up, which two muscles contract to make this happen?
- The superior rectus contracts so the eye can look up
2. The levator muscle contracts so the eyelid can go up.
What cranial nerve innervates the Levator?
CN IIII oculomotor
Where does the Levator muscle originate and inset?
Originates posteriorly from the lesser wing of sphenoid and courses forward to the superior orbit above the superior rectus, where is blends in. Anteriorly, it condenses to form whitewall’s ligament and then turns into the Levator aponeurosis.
Superiorly, the aponeurosis fuses with the orbital septum.
Medially and laterally, it fuses with the medial and lateral canthal tendon (or medial and later palpebral ligaments)
Anteriorly, attaches to the anterior surface of the tarsal plates, muscle fibers of the orbicularis oculi and the eyelid skin.
Which muscle divide the lacrimal gland into orbital and palpebral lobes?
The Levator palpebrae.
The orbital portion is posterior and the palpebral portion is anterior and can sometimes be seen when the gland is inflamed.
The Levator’s attachment to the skin forms the___
superior palpebral sulcus/crease! This divides the eyelid into a tarsal and septal region. May be absent during aging, and certain ethnicities (asian).
The Levator is an antagonist of which other muscle?
Orbicularis oculi
Is Muller’s muscle smooth or skeletal
Smooth
Fun fact about Muller’s muscle
It is the only smooth muscle of the eyelid. It contracts to open the eyelids.
Where does muller’s muscle (upper and lower) originate from and insert into?
Upper:
Originates from the levator
Inserts at the superior border of the tarsus
Lower:
Originates from the capsulopalpebra fascia
Inserts at the lower border of tarsus
Does Muller’s muscle contact to open or close eyelid?
The muscle contracts to open the eyelids. Automatic, without thought. Only smooth muscle of the eyelid.
Is capsulopalpebral fascia a muscle?
no
What connective tissue functions as the main retractor of the lower lids?
Capsulopalpebral fascia
Where does the capsulopalpebral fascia attach too?
The lower border of the tarsus, muscle fibers of the orbicularis oculi and skin.
Attachment of the capsulopalpebral fascia to the skin forms what
Inferior palpebral sulcus
Palpebral conjunctivia
Thin, transparent mucous membrane that lines the underside of the lids. Also contains the goblet cells.
Accessory lacrimal glands of krause and wolfing
Apart of the palpebral conjunctiva. They secrete the aqueous portion of the tear film.
What glands secrete the aqueous portion of the tear film
Krause and wolfing
