Eyelids Anatomy & Physiology Study | OPT 221 Biology

Where do the upper eyelids extend from?

conjunctival fornix to the superior orbital rim

Where do the lower eyelids extend from?

Conjunctival fornix to the nasojugal and palpebromalar sulci

Where do the upper and lower eyelids meet?

canthus (lateral lies directly on the globe, medial is separated from the globe by the lacrimal lake)

What is the name of the opening between the upper and lower eyelids?

palpebral fissure

How wide is the palpebral fissure horizontally?

~30 mm

How long is the palpebral fissure vertically?

~10 mm

How is the length of the vertical palpebral fissure calculated?

MRD-1 + MRD-2

What is the marginal reflex distance-1?

distance between corneal reflex and the upper lid margin (4-4.5mm)

What is the marginal reflex distance-2?

distance between the corneal reflex and the lower lid margin (>5 mm)

What is the function of the eyelid skin?

prevents microbes from causing infections in underlying tissue

What is the thinnest skin in the body?

eyelids (<1 mm); thin because of attenuated dermis and minimal hypodermal tissue (can still swell dramatically)

What is the skin of the eyelid composed of (what are the layers)?

-epidermis

-dermis

-hypodermis

During eyelid reconstruction surgery, what is the ideal choice for a skin graft?

contralateral eyelid

Where is hypodermis absent in the eyelids?

tarsal region

What tissue lines the inner eyelids?

palpebral conjunctiva; it is a thin transparent mucus membrane

What is the tarsal plate composed of?

dense connective tissue; fibroblasts, collagenous fibers, elastic fibers, ground substance

How thick is the tarsal plate? How far does it extend?

-1-1.5 mm thick

-extends horizontal length of eyelid (30 mm)

-9-11 mm superior, 4-5 mm inferior

Where does the superior tarsus extend from?

eyelid margin to the superior palpebral sulcus

Where does the inferior tarsus extend from?

eyelid margin to the inferior palpebral sulcus

Approximately how many meibomian glands are located in each eyelid?

-30-40 in the UL

-20-30 in the LL

What is the orbital septum composed of?

dense connective tissue; fibroblasts, collagenous fibers, elastic fibers, ground substance (extends entire rim of the orbit to the tarsal plate)

What is the function of the orbital septum?

anterior barrier of the orbit and separates the eyelids and lacrimal sac from the orbit; prevents facial/eyelid/nasolacrimal infections from entering the orbit

-also keeps orbital fat in place

What is the function of the orbicularis oculi?

protracts the ULs and LLs (contraction closes the eyelid)

What are fibers of orbicularis oculi near the lid margin called?

Riolan's muscle

What is the function of riolan's muscle?

maintains the lid margin close to the globe and aids in the lacrimal pump mechanism

What are the antagonists of the orbicularis oculi muscle?

levator palpebrae and frontalis

What is the function of the levator palpebrae muscle?

main retractor of the ULs (contraction opens the ULs); blends with the superior rectus so when eye moves up, eyelid retracts

What is the tendon of the levator muscle called?

levator aponeurosis

What does the levator aponeurosis do?

fan shaped muscle that divides the lacrimal gland into orbital and palpebral lobes

The levator aponeurosis attaches to the skin and forms what?

superior palpebral sulcus (8-12 mm above the UL margin); this divides the eyelid into a tarsal region and a septal region

When can the superior palpebral sulcus be absent?

if the levator aponeurosis attaches to the skin more inferiorly (aging changes, certain ethnicities)

What is the antagonist of the levator muscle?

orbicularis oculi

What is Muller's muscle?

smooth muscle that is an accessory retractor of the ULs and LLs (contraction opens the eyelids)

Where does Muller's muscle originate from?

-UL: levator muscle

-LL: capsulopalpebral fascia

What is the capsulopalpebral fascia?

connective tissue sheet that functions as the main retractor of the LLs

Where do capsulopalpebral fascia fibers arise from?

lockwood's ligament and sheaths of the IR and IO; fuse with orbital septum forming a common fascial sheet

What does the attachment of the capsulopalpebral fascia to the skin form?

inferior palpebral sulcus (5 mm below the LL margin); this divides the eyelid into the tarsal region and septal region

What is Whitnall's ligament?

superior transverse ligament surrounding the levator; allows for a change of the functional origin of the levator palpebrae superioris muscle allowing for the superior tarsus to be elevated superiorly rather than directly towards the origin at the sphenoid bone

What are the layers of the eyelids?

-anterior lamella

-middle lamella

-posterior lamella

What makes up the anterior lamella?

-skin

-orbicularis oculi muscle

What makes up the middle lamella?

-orbital septum

-retractor muscles

-fat

* note that this area is not present in the tarsal plate

What makes up the posterior lamella?

-tarsal plate (not present in the superior portion of the UL or inferior portion of LL)

-palpebral conjunctiva

What are the anterior and posterior lamellae divided by?

gray line; located between the meibomian gland opening and eyelashes

The gray line is the surgical landmark for what?

the anterior border of Riolan's muscle

What is present at the lid margin?

-eyelashes

-lacrimal papilla/puncta

-mucocutaneous junction

-lid wiper region

-meibomian gland orifices

What secretes sebum into the hair follicle of the eyelashes?

glands of zeis (holocrine, sebaceous glands); this coats the eyelash shaft and keeps them from becoming brittle while also keeping the eyelid margin lubricated

What secretes sweat into the hair follicle of the eyelashes?

glands of Moll (apocrine, sweat glands); function is possibly immune

What do meibomian gland orifices do?

secretes oil onto the skin just in front of the mucocutaneous junction

What are the lacrimal papillae or puncta?

elevation of tissue in the medial portion of the eyelids; puncta are the beginning of the nasolacrimal drainage system

What is the mucocutaneous junction a transition zone between?

palpebral conjunctiva and skin

What is the lid wiper region?

-elevated strip of palpebral conjunctiva just posterior to mucocutaneous junction

-comes into contact with the globe during blinking

What is responsible for sensory innervation of the eyelids?

CN V (V1 and V2)

What branches of the ophthalmic nerve (V1) innervate the eyelids?

-nasociliary nerve

-frontal nerve

-lacrimal nerve

What does the nasociliary nerve branch into (think specifically what innervates the lids)?

infratrochlear nerve (innervates UL and LL)

What does the frontal nerve branch into (think specifically what innervates the lids)?

-supraorbital nerve (UL)

-supratrochlear nerve (UL)

What branches of the maxillary nerve (V2) innervate the eyelids?

infraorbital nerve (LL)

What is responsible for motor innervation of the orbicularis oculi muscle?

CN VII; temporal and zygomatic branches

What is responsible for motor innervation of the levator muscle?

CN III; superior division innervates the levator muscle

What is responsible for motor innervation of Muller's muscle?

sympathetic fibers (smooth muscle=involuntary)

What arteries are responsible for blood supply to the eyelids?

-internal carotid artery

-external carotid artery

What branches of the internal carotid arteries provide blood supply to the eyelids?

-palpebral arcades supply UL and LL (superior and inferior marginal and superior and inferior peripheral)

anastomose between lateral palpebral arteries and medial palpebral arteries

What branches of the external carotid arteries provide blood supply to the eyelids?

-angular branch of facial artery supplies medial LL

-infraorbital branch of maxillary artery supplies LL

What do the lateral palpebral arteries branch from?

lacrimal artery (branch of ophthalmic artery)

What do the medial palpebral arteries branch from?

direct branch of ophthalmic artery

Describe the physiology/functions of the eyelids.

-protects the globe from potentially harmful stimuli

-prevents desiccation of the ocular surface

-contain structures that produce the tear film

-distributes the tear film upon blinking

-moves tears toward the lacrimal drainage system