Conjunctiva, Cornea, Sclera, Limbus

where is the conjunctiva located?

covering the anterior sclera & inner eyelid

NOT ON CORNEA

the conj can be broken into... (3)

bulbar, fornix, palpebral

where is the palpebral conj located?

covering the inner eyelid

where is the bulbar conj located?

covering the sclera

where is the conjunctival fornix located

U-turn between the bulbar & palpebral conj

all conjunctiva is composed of an ____ layer and a _____ layer

epithelium & stroma

what cell is responsible for secretions in the conjunctiva?

goblet cells

the palpebral conj can be broken into...

marginal, tarsal, orbital

what type of epithelium is in the palpebral marginal conjunctiva?

stratified squamous

what type of epithelium is in the palpebral tarsal conjunctiva?

stratified columnar

what type of epithelium is in the palpebral orbital conjunctiva?

stratified colmnar

the conjunctiva is thickest at what portion?

fornix

what type of epithelium is in the conjunctival fornix?

stratified columnar

t or f: the conjunctival fornix is present superiorly, inferiorly, medially, and laterally

false, there is no fornix in the medial canthus, the plica semilunaris is there instead

the conj fornix is held in place by...

muscle fascia/aponeurosis

what type of epithelium is in the bulbar sclera conjunctiva?

stratified columnar

what type of epithelium is in the bulbar limbal conjunctiva?

stratified squamous

most common type of collagen

type I

collagen used for wound healing

type III

collagen found in basement membranes

type IV

collagen used for anchoring

type VII

what is the main cell junction found in conjunctival epithelium?

leaky tight junctions

t or f: melanocytes/melanin granules are present in the conjunctiva

true

t or f: conjunctival stem cells can be found in the conjunctiva epithelium

true

what is the difference between a cell with a high content of keratin vs melanin?

keratin - stability/structure to cells

melanin - protection from oxidative stress

unkeratinized conjunctival epithelium is directly continuous with... (3)3

corneal epithelium

eyelid epidermis (keratinized)

nasolacrimal drainage epithelium

goblet cells of the conjunctiva originate at _____

basal layer of epithelium

t or f: goblet cells are capable of merocrine, apocrine, and holocrin secretion

true (merocrine is most common)

where is the density of goblet cells greater: medial or lateral canthus?

medial

inflammation will __(increase/decrease)__ the number of goblet cells

increase

apical surface modification of conjunctival epithelium

microvilli & glycocalyx

the conjunctival stroma can be broken into what 2 layers?

outer adenoid & deep fibrous

what type of tissue makes up the conjunctival stroma?

loose CT

what components are present in the outer adenoid layer?

lymphocytes, APCs, lymphatic vessels, blood vessels, collagen type I

what components are present in the deep fibrous layer?

fibroblasts, collagen type I, lymphatic vessels, blood vessels,

few lymphocytes

pingueculae

raised, yellow thickening of the conj stroma

caused by cellular proliferation, deposition of hyaline, and elastotic degeneration

pterygium

triangle-shaped growth of the conj extending into the cornea

caused by degeneration of collagen and fibrovascular proliferation in stroma

t or f: both pingueculae and pterygium are disorders of the conjunctival stroma

true

what is the difference between crypts of Henle and microvilli in conjunctiva?

crypts - folds in epithelium AND stroma

microvilli - fold in epithelium

does the plica semilunaris contain both conj epithelium and stroma?

yes

third eyelid is also called...

nictitating membrane

where are the conjunctival blood vessels more numerous: the palpebral or bulbar portion?

palpebral

where are the conjunctival lymphatic vessels more numerous: the outer adenoid or deep fibrous layer?

outer adenoid

what immune cells do you expect to find the the conj stroma?

neutrophils, lymphocytes, plasma cells, macrophages, dendritic cells

where are lymphoid cells more numerous: the palpebral or bulbar conjunctiva?

palpebral

t or f: conjunctival stroma contains lymphoid follicles that grow as we age

false, the lymphoid follicles get smaller as we age

all lymphatic vessels lead to...

the heart

circle of teichmann

smallest lymphatic vessels that encircle the cornea

radial lymph vessels

peripheral to circle of teichmann

vessels are slightly bigger than the circle of t

pericorneal lymphatic ring

largest lymphatic vessels circling the cornea

outwards from the limbus

peripheral to radial lymph vessels

lymph flows from cornea -> ____ -> ____ -> ____ -> ____ -> ____ -> heart

circle of teichmann -> radial lymph vessels -> pericorneal lymphatic ring -> superficial parotid/submandibular nodes -> deep cervical lymph node

the parotid lymph nodes receive drainage from...

lateral lids & conj

the submandibular lymph nodes receive drainage from...

medial lids & conj

the deep cervical lymph node receives drainage from...

the parotid & submandibular lymph node

function of conjunctiva

prevent desiccation

increase mobility

provide a barrier against microorganisms and foreign bodies

inflammatory response from goblet cells

fibrous tunic

sclera + cornea

megalocornea

enlarged cornea

microcornea

small cornea

which is thicker: the central or peripheral cornea?

peripheral

which has a larger radius of curvature: the anterior or posterior surface of the cornea?

anterior

external scleral sulcus

junction between the cornea & sclera

which has a larger radius of curvature: the cornea or sclera?

sclera

where does the cornea get most of its nutrients?

O2 mostly from environment/tears

all other nutrients from aqueous humor

5 layers of the cornea

epithelium

Bowman's membrane

stroma

Descemet's membrane

endothelium

what type of tissue is corneal epithelium?

unkeratinized statified squamous

3 main cells types/layers of corneal epithelium

basal cells, wing cells, superficial cells

the basement membrane of corneal epithelium is made by...

basal cells

the basal cells are attached to the basement membrane by...

hemidesmosomes

how many layers of basal cells are in the corneal epithelium?

1

what is the shape of basal cells?

columnar

what junctions are between basal cells?

gap & desmosomes

the wings cells are attached to the basal cells by...

desmosomes

how many layers of wing cells are in the corneal epithelium?

2-3

what is the shape of wing cells?

polyhedral with wing-like projections

what junctions are between wing cells?

gap & desmosomes

how many layers of superficial cells are in the corneal epithelium?

2-3

what is the shape of superficial cells?

squamous

what junctions are between superficial cells?

desmosomes & complete tight junctions

as you move toward the apical surface of the corneal epithelium, the number of tight junctions _______ and the number of gap junctions _____

tight junctions increase

gap junctions decrease

corneal epithelial cells have 2 types of apical surface modification to increase their surface area. what are they?

microvilli & microplicae

which tissues have a mucin glycocalyx?

conj, cornea, and limbus epithelium

t or f: the most superficial cells of the cornea are viable

true

t or f: corneal epithelial cells are constantly being shedded from the surface

true

what characteristics of the corneal epithelium contribute to its transparency?

smooth surface (tear film)

lack of intercellular space (decrease light scatter)

smaller & fewer organelles

t or f: corneal epithelial cells have a long lifespan

false

the basement membrane is also called...

basal lamina

2 layers of a basement membrane

lamina lucida & lamina densa

what component is found in the lamina lucida?

laminin

what component is found in the lamina densa?

collagen IV

what layer is underneath the corneal epithelial BM?

Bowman's layer

t or f: basal epithelial cells are able to regenerate the BM quickly

false, regeneration can take months

function of BM

attach the epithelium to underlying tissue

t or f: fibroblasts are present in Bowman's layer

false, Bowman's is acellular

what components are found in Bowman's?

tightly packed collagen type I & VII

ground substance

t or f: Bowman's layer is regenerated quickly by fibroblasts

false, Bowman's cannot be regenerated; it is created in utero and does not contain any cells

what percentage of water is held in the corneal stroma?

78%

what components are found in corneal stroma?

collagen type I organized into lamellae

ground substance

keratocytes

APCs

what are the important proteoglycans/GAGs in the corneal stroma?

keratocan, lumican, decorin

anterior vs posterior corneal stroma: which is more ordered?

posterior

anterior vs posterior corneal stroma: which has more interweaving?

anterior