Conjunctiva Flashcards
Conjunctiva
thin, vascularized mucous membrane that lines eyelids
major mucous producer = goblet cells in epithelial layer
reflected at fornices onto anterior surface of eyeball
conjunctival sac - forms potential space
Parts of conjunctiva
fornix with redundant conjunctiva
bulbar
palpebral
conjunctival sac
cul de sac
Conj vs. potential combating infection
highly vascular
cell types for initating and participating in defensive inflammatory rxn
surface has microvilli and enzymes to engulf and neutralize foreign particles
conjunctiva epithelium
stratified squamous non-kertinizing epithelium
more stratified columnar/cuboidal in tarsal, fornix and bulbar epithelium
2-15 cell layers thick: basal, intermediate, and superficial cell layers
-rests on substantia propria (stroma)
- rests on basement membrane, attached by hemi-desmosomes
- epithelial cells connected to one another by desmosomes (attached to intermediate filaments of keratin)
cell types in epithelium
microvilli coatced with mucopolysaccarhides
goblet cells (mucous secreting)
melanocytes- protective, absorb UV
langerhan cells
intraepithelial lymphocytes
many polymorphonuclear leukocytes found in inflammatory conditions
langerhan cells
similar in morphology to macrophages
functino: take up and process microbial antigents
present in suprabasal portion of conjunctival epithelium at limbus
melanocytes
scattered in basal layer of limbal and bulbar epithelial
may play protective role for stem cells against UV exposure
goblet cells
large cells 25 u x 25 u
mucin granules within cytoplasm of goblet cells => released by apocrine secretion
production of mucus
stabilizes tear film
palpebral (tarsal) conjunctival epithelium
5-6 layers thick
palpebral conj epithelium more cuboidal
numerous and prominent microvilli on free surface of palpebral conj
cells with long microvilli line deep crypts that extend into epithelium
substantia propia (stroma)
connective tissue layer beneath epithelium with great anti-infectious capability
cell types: mast cells (histamine), lymphocytes, plasma cells and neutrophils
layers of conjunctiva
epithelium, substantia propria => adenoid layer (lymphoid layer = lymph) and fibrous layer (blood supply and innervation)
Substantia propria layers
2 layers:
superficial lymphoid layer (not present at birth => develops few months post-natally)
-most developed in fornices
deeper fibrous layer: collagenous and elastic tissue, blood vessels, nerves, glands of Krause, and larger lymph vessels
pinguecula
localized, elevated, yellowish-white excresence noted medially and laterally close to limbal margin (localized at palpebral opening usually 3 or 9 position)
represent age-related elastotic degeneration including collagen breakdown of the stroma
initial event: limbal stem cell damage by uv exposure causing fibroblasts producing elasting fibers twisted and degradation of collagen fibers (usually medial and later more exposed to UV)
underlying sclera acts w/ high reflectivity to furth back expose the tissue to UV (Sclera reflects uv to conj => more damage)
pterygium
basophilic degeneration of bulbar conjunctival stroma
histopathology: same as piguecular but with corneal involvment; elastotic degeneration of collagen and fibrovascular proliferation (limbal stem cells affected in pterygium => more visual consequences)
usually damage to limbal stem cells by prolonged UV exposure initial event to cause pterygium
other factors affecting: UV, wind, sand
3 regions of conjunctiva
palpebral conjunctiva (eyelids)
conjunctival fornices (redoubled fold of conjunctiva)
bulbar conjunctiva (eyeball)
palpebral conjunctiva
lines inner surfaces of eyelids; tightly bound to tarsal plate
-subepithelial substantia propria = thin
lacrimal puncta opens on palpebral conjunctiva
lining of palpebral conj continous with lining of inferior meatus of nasal cavity
punctal opening and lining is continous with lining of canaliculi, lacrimal sac, and nasolacrimal duct
dacryocystitis: infection in lacrimal sac
zones of palpebral conjunctiva (3)
marginal zone: margin of lid; transition between skin of eyelid and conj. epithelium
-puncta opens on this zone
tarsal zone: thin, transparent, tarsal glands beneath; very vascular (meibonian glands within tarsal zone)
orbital zone: between upper border of tarsus and fornix
subtarsal sulcus (in palpebral conjunctiva)
2mm from lid margin; important in trapping and removing foreign particles and debris
in marginal zone
palpebral conj represents area for pathologic changes related to infectious and inflammatory processes or allergic
Follicles
accumulation of lymphocytes; miniature lymph nodes composed of lymphocytes, macrophages, and plasma cells
(think substantia propria when follicles seen)
normal in childhood
consistent with dx of viral infection or allergic tissue response (think viral/allergic)
conjunctival follicle
tissue reaction to irritation
no significant difference among follicles caused by identifiable irritant, unknown agent, and noted in acute infections follicular conjunctivitis
follicle size related to severity and duration of inflammatory stimulus
where are follicles found and how do they look
usually inferior palpebral conj and inferior fornix
round, discrete, clear mound encircled by vascular ring: 0.5 to 5 mm dia.
could be limbal follicles
papillae/ papillary hypertrophy
a nonspecific reaction occurring in chronic and acute forms of conjunctivitis; more typically on upper tarsal (palpebral) conjunctiva
consists of focal aggregates of acute inflammatory cells (PMN example)
has presence of blood vessels at center (follicles do not)
size of papillae
can be relatively small and give velvety appearing (in bacterial conjunctivitis)
or
giant papillae: found in allergic diseases or long standing contact lens wear
conjunctival papillae
reddish, flat topped raised areas
red velvety appearance to palpebral conj
central core of numerous dilated blood vessels with surrounding lymphocytes and covered by hypertrophic epithelium
consistent with bact. conjunctivitis
conjunctival fornix
continuous circular cul de sac, broken medially by caruncle and plica
in contact with and adherent to loose fibrous tissue derived from fascial sheaths of levator and recti muscles
superior fornix: 8-10 mm from limbus
inferior fornix: 8 mm from limbus
medially: replaced by caruncle and plica semilunaris
lateral: deep 14 mm from limbus
unites lid and bulbar conjunctiva
lies in a number of folds loosely attached to orbital septum
folds ensure mobility of globe and enlarge secretory surface
pseudoglands of henle
numerous goblet cells in fornix conjunctiva
bulbar conjunctiva
thin, transparent, mucous membrane
lies loosely on underlying tissue
3 mm from limbus becomes adherent to sclera and tenon’s capsule
some clinical correlates to bulbar conjunctiva
chemosis: tissue swelling
subconjunctival hemmorhage
limbal conjunctival epithelium
bulbar conj. epithelium approaching cornea
of layers: 10 - 15
no goblet cells at limbus
epithelium increasingly similar to corneal epithelium
palisades of vogt
radially oriented channels within stroma of limbal conjunctiva
stromal channels separated from another by ridges of epithelium
palisades = stromal channels + epithelium (rete pegs) + small nerves, blood vessels, lymphatics run length of papilla
house of limbal stem cells responsible for corneal repair
aka complicated microenviroment = limbal niche
malfunction of limbal stem cells proliferation
irritable eye, redness, decreased vision, photophobia, tearing, episodes of pain because cornea erosions
slit lamp eval shows dull and irregular corneal reflex: areas of opacification and pannus
impression cytology: presence of goblet cells; absence of differentiation as corneal cells (absence of keratin K3)
Conjunctiva glands (3)
Glands of krause
glands of wolfring
glands of henle
glands of krause
accessory lacrimal glands found deep in subconjunctival connective tissue of upper and lower fornix
42 in upper fornix
6-8 in lower fornix
glands of wolfring
accessory lacrimal glands
2-5 upper lid along border of upper tarsus
2 glands along inferior edge of lower tarsus
glands of henle (crypts of henle)
secrete mucous
occurs in palpebral conj. between tarsal plate and fornices
not true glands
folds of mucous membranes (lots of goblet cells)
caruncle
small, pinkish ovoid body in lacus lacrimalis (lacrimal lake) at medial angle of eye
medial to plica
nonkeratinized stratified squamous epithelial
modified skin possessing few fine colorless hairs and sebaceous glands (oil), sweat glands, accessory lacrimal glands
plica semilunaris
half moon shaped fold
lateral to caruncle
contain goblet cells (like bulbar conj)
highly vascularized
arterial supply to conjunctival (2)
2 palpebral arches and 1 artery:
peripheral palpebral arch
marginal palpebral arch
anterior ciliary artery
opthalmic artery -> medial palpebral arter -> marginal arterial arch and peripheral arterial arch
ophthalmic artery -> lacrimal artery -> lateral and medial palpebral artery
conj. capillaries non-fenestrated
marginal palpebral arch
3 mm from free border of eyelid
b/n tarsus and obicularis oculi muscle
arteries on posterior surface of tarsus supply inferior palpebral conj. of superior lid and superior palpebral conj. of inferior lid
peripheral palpebral arch
supplies superior palpebral conj and superior & inferior conj. fornices
branches of the peripheral arch form the posterior conj. artery to vascularize bulbar conj
pericorneal plexus
posterior conj. arteries proceed toward limbus => anastomose with anterior conj. arteries
anterior conj. arteries branched from the anterior ciliary artery
posterior and anterior conj. arteries form pericorneal plexus
hyperemia
conspicuous clinical sign of acute conj. inflammation because dilation of posterior conj vessels
if anterior ciliary vessels are involved, pericorneal area has deeper congestion => hypermia => inflammation in deeper structures (like anterior uvea)
hypoyon
pus in anterior chamber
conjunctival veins
accompany conjunctival arteries
drain to: palpebral veins or superior and inferior ophthalmic veins
conj. lymph drainage
mediation of immunological rxn that occur in diseases
arranged as superficial and deep plexus in submucosa (substantia propria)
lateral -> superficial parotid nodes
medial -> submandibular nodes
viral infection produces lots of lymphocytes -> preauricular will be swollen
sensory innervation
bulbar conj: long ciliary nerves (nasociliary branch of CN 5)
- unmyelinated nerves
superior palpebral and fornix: frontal branch of CN5 and lacrimal branch of CN 5
inferior palpebral and fornix:
- lateral: lacrimal branch of CN5
- medial: infraorbital nerve from CN5 maxillary
