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
In regards to eyelid disease, list muscular problems with the eyelid.
- ptosis, entropion, ectropion
- paralysis of orbicularis (CNVII)
- paralysis of levator (CNIII)
Define entropion and ectropion
Entropion - a condition in which the eyelid is rolled inward against the eyeball,
Ectropion - eyelid turned outwards, away from the eyeball
In regards to eyelid disease, list Eyelid gland abnormalities. [4]
- Meibomium gland dysfunction (lipid dry eye)
- Internal hordeolum (meibomium infection)
- External hordeolum (zeiss or moll infection)
- Chalazion (inflammatory, non-infective blockage of meibomium)
What does paralysis or orbicularis result in?
Prevents eyelid closure
What does paralysis of levator result in?
Drooping lid or ptosis
Which cranial nerves are involved with:
A) Palpebral Motor Innervation
B) Palpebral Sensory Innervation
Motor: Cranial Nerve VII - Facial nerve
Sensory: Cranial Nerve V - Trigeminal nerve
What are the 3 divisions of the Trigeminal Nerve? And what nerves do these divisions innervate?
- Opthalmic Division (V1)
- lacrimal nerve (smallest)
- frontal nerve (largest)
- nasociliary - Maxillary Division (V2)
- infra-orbital nerve - Mandibular Division
- info not needed/given
Which nerve is larger, the lacrimal nerve, frontal nerve or nasociliary?
frontal nerve
Which division of the trigeminal nerve is involved with superior eyelid sensory innervation? which nerves innervate?
Opthalmic division (V1)
- mainly supra-orbital
- also supra-trochlear, infra-trochlear, and lacrimal
Which division of the trigeminal nerve is involved with inferior eyelid sensory innervation? Which nerves innervate?
Maxillary Division (V2) - mainly infra-orbital
Name the regions and branches of the Orbicularis Oculi muscle involved with palpebral motor innervation. [2 regions, 3 branches]
Upper region: temporal & superior zygomatic branches
Lower region: lower zygomatic branch
Where does ocular blood supply come from?
Ophthalmic artery
List the major branches of the ophthalmic artery. [5]
Central retinal artery muscular artery lacrimal artery short, long posterior ciliary artery anterior ciliary artery
Fill in the blank: Most of the external arteries to the eyelid and adnexa come from the ________?
ophthalmic artery
Which 4 branches of the ophthalmic artery are the main branches involved in eyelid/palpebral blood supply?
dorsal nasal artery supratrochlear artery (above trochlear muscle) supraorbital artery (above orbit) lacrimal artery (close to gland)
What arteries does the lacrimal artery give rise to? [1]
Lateral palpebral arteries
What arteries does the dorsal nasal artery give rise to, what branches?
Medial palpebral arteries
- superior and inferior branches
What to the lateral palpebral and medial palpebral arteries do once they reach the eyelid?
Each of them divides into 2 branches that form 2 arcades in each eyelid:
- peripheral arcade
- Marginal arcade
Where are the 2 arcades in each eyelid located?
Peripheral arcade: superior to tarsal plate
Marginal arcade: closer to lid margin
Describe the lymphatic and venous drainage of the eyelid
Venous drainage:
- Eyelid veins larger/more numerous
- Drainage into several large vessels in the face
Lymphatic drainage
- Restricted to region anterior to the orbital septum
- Drainage occurs via superficial parotid and submandibular lymph nodes
List the 6 major layers of the eyelid [from front to back]
- skin
- subcutaneous connective tissue
- striated muscle (orbicularis)
- submuscular connective tissue
- tarsal plate
- palpebral conjunctiva
What are the glands of Zeis & Moll, and what is their role in the skin?
They are sebaceous glands
- they produce sebum, an oily substance that coats the eyelashes/hair and keeps them from being too brittle
Explain the Mucocutaneous Junction
Is the transition point from skin to mucosal epithelium
Compared to skin, mucosal epithelium ……… [4]
- contains goblet cells
- is non-keratinised
- is thinner
- is smooth due to absence of lamina propria papillae
List the features of subcutaneous connective tissue [4]
- is loose collagenous connective tissue
- is traversed by filaments from the levator palpebrae tendon
- has no fat
- region of pooling – cause black eye
Describe the features of the striated muscle layer of the eyelid
Orbital portion up the top, septum portion in the middle and pretarsal at the bottom
Strip of pretarsal orbicularis
- Guides Meibomian gland secretions
- More separated and posterior than pretarsal: Riolan’s msucle (important for secretion)
- Pockets of muscle
- When you close eyelids = Activation of muscles = Squeezes out
Describe the features of the sub-muscular layer of the eyelid
Similar to subcutaneous
- Lies between orbicularis and tarsal
- Can see faint grey line (dividing lid margin)
If injured or swollen, fluid accumulation (more prominant)
- Divides anterior/posterior lid
Describe the features of the tarsal plate layer of the eyelid
- Thickness varies (thick centrally, thin peripherally)
- Dense fibrous CT
- Dividing line stops before lid margin = Structural importance = Superior/inferior lid margins
Maintains shape and firmness of lids
- Meibomian glands embedded
Describe the features of the palpebral conjunctiva layer of the eyelid
palpebral conjunctiva layer of the eyelid
- Mucous membrane (mainly cuboidal/columnar epithelium)
- Contains goblet cells - mucin
- No mucin = Can’t bind
Secretes AH into tear film (10% contribution)
- Accessory lacrimal glands
- Tarsal glands of Wolfring and Klause
Describe the 3 zones the palpebral conjunctiva can be divided into.
- Marginal zone: transition b/w skin and conjunctiva proper
- Tarsal zone: thin, adherent, highly vascular (red colour)
- Orbital zone: between tarsal upper border and fornix, loosely attached
list the regions of the conjunctiva
Bulbar - limbal, - scleral Forniceal Palpebral - orbital, - tarsal, - marginal
How far does the conjunctiva extend?-
Extends from eyelid margins anteriorly, providing a lining to the eyelids, before turning sharply upon itself to form the fornices
From here, it is reflected onto the globe, covering the sclera up to its junction with the cornea
True or False: The conjunctiva forms a ‘sac’ which opens anteriorly through the palpebral fissure.
True
Describe the features of the Forniceal conjunctiva.
- it forms an annular cul-de-sac
- it has 4 zones: superior, inferior, lateral, medial
- is adherent to areolar tissue
- is well vascularised
Describe the features of the Bulbar (ocular) conjunctiva
- thin underlying sclera visible
- tied to subadjacent structures by areolar tissue; mobile
- at about 3mm from the cornea, conjunctiva and sclera become adherent
- sensory innervation from long ciliary nerves (branches of nasociliary nerves)
Describe the histological structure of the conjunctiva
- epithelium = stratified columnar cells (2-5 layers)
- rests on a lamina propria (loose connective tissue)
Limbus: change to stratified squamous non-keratinised epithelium (continuous with cornea)
Goblet cells: scattered along the surface (most numerous infero-nasal)
Function of glands
secretion
What type of glands are found in eyelids? [4]
Tarsal/Meibomiam (lipid secreting) Ciliary glands of Moll (sweat) Glands of Zeis (sebaceous) Accessory lacrimal glands - Krause, Wolfring
*Way to remember
TCGA – it’s the 4 dna bases! Thymine, Cytosine, Guanine, Adenine
But instead it’s tarsal, ciliary glands, glands of zeiz, accessory lacrimal
True or False: Making Bio flashcards is suffering and takes too long
True
True or False: Meibomian glands are not associated with cilia
True
Where is the nasojugal sulcus?
Inferior and medial/nasal.
Way to remember: it’s like the lines on itachi’s face from naruto. The one closest to the nose
What is the name of the inferior and lateral line on itachi’s face under his eye?
Malar sulcus
