Flashcards in BS - Eyelids and Conjunctiva - Week 2 Deck (93):
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?
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)?
What kind of muscle is Mullers muscle?
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.
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?
-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.
Short posterior ciliary
Long posterior 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.
What are the 4 main arterial branches to the eyelid?
What arteries does the lacrimal artery give rise to?
Lateral palpebral arteries
What 2 arteries does the dorsal nasal artery give rise to?
Superior and inferior medial palpebral arteries
Where are the peripheral and marginal arcades found, and what two arteries contribute to their formation and how?
Peripheral - superior to the tarsal plate
Marginal - closer to the lid margin
Formed by the lateral palpebral, superior, and inferior medial palpebral arteries.
Each divides into two branches forming the arcades.
Compare eyelid veins to arteries in size and numbers.
Eyelid veins are larger and more numerous than arteries.
Name the two venous arcades.
Superior and inferior venous arcades, both found overlying the tarsal plate of each eyelid.
Where can the transverse facial vein be found?
A peripheral vein found near the margin of the orbit laterally on the frontal process of the zygomatic bone.
Where can the superior palpebral vein be found?
A peripheral vein found along the superior margin of the orbit.
Where is the lymphatic drainage of the eyelids restricted to?
The region anterior to the orbital septum.
How does lyphatic drainage occur in the eyelids?
Via superficial parotid and submandibular lymph nodes.
Name the 6 major layers of the eyelids, from superficial to deep.
Subcutaneous connective tissue
Submuscular connective tissue
What is the thickness of the skin overlying the eyelids like, and what does this allow for?
Very thin, allowing it to fold easily.
What three structures can be found on skin overlying the eyelids?
Short, fine cilia
Miniature sweat glands
Modified cilia forming lashes
What are glands of zeis and moll?
Modified sebaceous and sweat glands found on skin overlying the eyelids
What is the musculocutaneous junction?
Transition from skin to mucosal epithelium
Compare mucosal epithelium to skin, naming 4 differences.
Has goblet cells
Is smoother due to the absence of lamina propria papillae
Can adipose tissue be found in the subcutaneous connective tissue?
Where does blood pool when a black eye injury is sustained?
Subcutaneous connective tissue.
In which region is the orbicularis oculi the strongest?
Which muscle is thought to have a role in meibomian secretion?
Which major eyelid layer is the submuscular connective tissue layer most similar to?
Subcutaneous connective tissue layer
What two structures does the submuscular connective tissue layer lie between?
Orbicularis oculi and tarsal plate
What is the visible divide between the anterior and posterior lid?
The submuscular connective tissue layer
What can happen to the submuscular connective tissue layer during injury?
What kind of tissue is the tarsal plate?
Dense fibrous connective tissue
Describe the thickness of the tarsal plate centrally vs peripherally.
Thick centrally, thinner peripherally.
Peripherally, what is the tarsal plate continuous with?
True or false
The tarsal plate extends to the lid margin
False, it does not
Within what structure are the meibomian glands embedded in?
The tarsal plate
Which major layer of the eyelid are goblet cells found in?
The palpebral conjunctiva
What is the function of goblet cells?
Lubrication and wetting properties
What are accessory lacrimal glands?
Similar to lacrimal glands, but scattered throughout the palpebral conjunctiva
What is the palpebral conjunctiva composed of, and what are the two main shapes cells here take?
Mucous membrane, mainly cuboidal or columnar epithelium
Name the three subdivisions of the palpebral conjunctiva. Name their locations, and their appearance.
Marginal - transition zone between skin and conjunctiva
Tarsal - thin, adherent, and highly vascular (red)
Orbital - found between the upper tarsal border, and the fornix, loosely attached
Consider a sagittal cross section of the eye and eyelids. Name the 6 regions of the conjunctiva beginning with the inferior border of the eyelid, moving superiorly, then back down inferiorly along the eyeball. Categorise them by their subdivisions if applicable.
How many zones does the forniceal conjunctiva have? Name them. What is it adherent to? Is it richly or poorly vascularised?
4 zones, superior, inferior, lateral, and medial
Adherent to areolar tissue
Is the sclera visible underneath the bulbar conjunctiva?
At what distance from the cornea does the sclera and conjunctiva become adherent?
From which nerve does the bulbar conjunctiva receive sensory innervation? Name which nerve it is a branch of.
Long ciliary nerve, branch of the nasociliary nerve.
How many cells thick is the conjunctival epithelium, what kind of cells are they, and on what does it rest? What kind of tissue is this surface?
Epithelium is 2-5 cells thick of stratified columnar cells.
Rests on the lamina propria, loose connective tissue
Describe the cell type change from conjunctival epithelium to the limbus.
Cells go from stratified columnar cells to squamous non-keratinised epithelium
How are goblet cells arranged on the conjunctiva?
Name the five types of glands found within the eyelids, and what they secrete if applicable.
Ciliary glands of moll (sweat)
Glands of zeis (sebaceous)
How do meibomian/tarsal glands appear histologically?
Bunch of grapes
Are meibomian/tarsal glands associated with cilia?
How are meibomian/tarsal glands arranged on the eyelids, and in what numbers?
Vertically, 25 upper, 20 lower
Where is the main body of the tarsal/meibomian glands found?
Within the tarsal plate
Do meibomian/tarsal glands have a rich or poor neural supply?
What do meibomian/tarsal glands secrete and why?
Meibum, lipids preventing overflow of tears, leaving an oily film over the tears which acts to retard evaopration
What are ciliary glands of moll?
Modified apocrine sweat glands.
What do ciliary glands of moll secrete, and what are they associated with?
Have an aqueous-like secretion, and are associated with lash follicles.
Where do the ducts of ciliary glands of moll run into?
Into those of the glands of zeis
What are glands of zeis?
What are glands of zeis associated with? How many per structure?
Lashes, 2 per cilium
What do glands of zeis secrete, and what does this prevent?
Secretes sebum, and prevents lashes drying and becoming brittle