Conjunctiva: Ocular Anatomy

What is the conjunctiva?

Thin, semi-transparent mucous membrane

What is the conjunctiva continuous with?

Cornea at limbus and skin at mucuocutaneous junction of eyelids

What are the functions of conjunctiva?

Lubrication of ocular surface, reduces friction, provides physical and chemical antimicrobial barriers, and limbal epithelium makes stem cells for corneal epithelium renewal.

What are the 3 sections of the conjunctiva?

Bulbar conjunctiva, palpebral conjunctiva, and forniceal conjunctiva

What does the bulbar conjunctiva cover?

Sclera NOT cornea

What does the palpebral conjunctiva line?

Inside surfaces of eyelids

What does the forniceal conjunctiva line?

Fornices to form cul-de-sac connecting palpebral and bulbar sections

What are the two subdivisions of the bulbar conjunctiva?

Limbal and scleral

What are the Palisades of Vogt?

Spoke-like projections that extend from the end of the cornea and are contained in the limbus

What's the function of the Palisades of Vogt?

Capture foreign objects and move them away from cornea

The bulbar conjunctiva are loosely attached, except at?

Limbus and extra ocular muscles insertion

What is Tenons capsule?

Dense connective tissue capsule that extends from limbus to optic nerve

What pierces Tenons capsule?

Extraocular muscles and optic nerve

What does Tenons capsule separate?

globe from orbital fat

What allows the eye to move laterally without tearing the bulbar conjunctiva and serves as floor of lacrimal lake?

Plica semilunaris

What does the caruncle contain?

Cilia, accessory lacrimal gland tissue, goblet cells, and numerous sebaceous glands

What highly innervates the caruncle?

CN V-1

What are the three subdivisions of the palpebral conjunctiva?

Marginal, tarsal, and orbital

What does the palpebral conjunctiva contain?

Goblet cells and accessory lacrimal glands

What is the mucocutaneous junction?

Transition between keratinizted epithelium of epidermis and nonkeratinized epithelium of conjunctiva at the marginal conjunctiva

What is the mucocutaneous junction covered with?

Lipids secreted by Meibomian glands

What are the four subdivisions of the fornix?

Superior, inferior, medial, and lateral

Where is the highest goblet cell density found, with immune structures present, and plenty of loose tissue?

Fornix

What is the conjunctival sac?

Potential space between palpebral and bulbar conjunctiva

Epithelial cells provide what to a cell?

Barrier and structural support

What type of epithelium does the palpebral conjunctiva have?

Stratified columnar or pseudostratified columnar epithelium

Forniceal conjunctiva epithelium overview

Thicker, with many goblet cells

Bulbar conjuctiva epithelium overview

Thinner, fewer goblet cells, may become stratified squamous near limbus

What is CALT?

Conjunctiva Associated Lymphoid Tissue

Where is CALT most abundant?

Palpebral conjunctiva and fornices

What is the key to ocular immune defense against pathogens entering the eye?

CALT

At the fornix and most of palpebral conjunctiva the epithelial tissue is __.

Stratified columnar

At the bulbar conjunctiva the epithelial tissue is __.

Stratified cuboidal

Near the lib margins the epithelial tissue is __.

Stratified squamous

Conjunctival epithelium exhibits microvilli. What are the microvilli used for?

Increasing surface area for secretion and absorption at the conjunctival surface and holding mucin later of tear film

Epithelial cells join to each other at upper surface via tight junctions called what?

Zonal occludens

What does Zonula occludens help with?

Maintaining tear film barrier on surface

Epithelial cels join to each other below tight junctions via what?

Zonula adherens

How do the zonula occludens and the zonula adherens work together?

Zonula occludens seal gaps at the surface to keep substances out and zonula adherens hold the cells together so the tissue can act as a sheet

Goblet cell distribution with uniform or nonuniform?

Nonuniform

Where is the lowest and highest amount of goblet cells?

Highest amount in fornices and lowest amount near limbus

What are Crypts of Henle?

Small pockets found in palpebral (tarsal) conjunctival epithelium

What's the function for Crypts of Henle?

Mucus secretion via goblet cells and trap dust/debris

Goblet cells reviewing parasympathetic and sympathetic nerve terminals. Do they work together or in opposition?

In opposition, parasympathetic are stimulators and sympathetic are inhibitory

What are Langerhans cells?

Specialized dendritic cells found in conjunctival epithelium and functions as immune system sentinels

What cause a densely pigmented ring at limbus or diffuse patches of pigment on bulbar conjunctiva?

Dendritic melanocytes

Preauricular node is used to drain what portion of upper and lower lid?

Lateral 2/3 of upper and lateral 1/3 of lower

Sub-mandibular node is used to drain what protein of upper and lower lid?

Medial 1/3 upper lid and medial 2/3 lower lid

What is the sensory innervation of the eyelid?

CN I(opthalmic) and CN V2(maxillary)

What does the parasympathetic innervation via CN VII do for the eyelid?

Vasodilation, goblet cells and accessory lacrimal gland stimulation

What is the vascular supply to the superior palpebral conjunctiva?

Supraorbital artery, supratrochlear artery and lacrimal artery

What is the vascular supply of inferior palpebral conjunctiva?

Infraorbital artery

What is the vascular supply of the bulbar conjunctiva?

Vascular arcades within eyelids

What drains both bulbar and palpebral conjunctiva?

Anterior ciliary veins

What is the most common cause of "urgent" eye care visits that shows blood under conjunctiva?

Subconjunctival hemorrhage