wk3: AED Lumps+Bumps 2 Flashcards
What is keratin?
a protein found in hair, nails, and outer skin. It is a long stranded filament that anchors cells to each other, which prevents cells from pulling apart to give skin its toughness, and the layering of filaments produces an impenetrable barrier
Where is keratin found? (3)
Hair
Nails
Skin
How is keratin made?
In keratinocytes via “cornification”
Describe “cornification” and the geographical distribution of keratin production
keratinocytes in the middle of the epithelium make a lot of keratin
as they do, they move towards the top of the epithelium
when at the top, the keratinocytes die, leaving a thick shell of keratin to form the tough outer layer of the skin
Describe the normal appearance of the conjunctiva
transparent mucous membrane
Compare the basic features of the skin with the conjunctiva (2)
Skin: epidermis with keratin; dermis
Conjunctiva: squamous cells and stroma (substantia propria ) (no keratin)
Where does the lymphatic network of the conjunctiva drain to? (2)
The pre-auricular and sub-mandibular nodes
What does lymphatic drainage from the conjunctiva mediate? (2)
Both innate and active immunity
What 3 components/areas is the conjunctiva divided into?
Palpebral Conjunctiva
Forniceal conjunctiva
Bulbar Conjunctiva
Where does the palpebral conjunctiva start?
at the junction of the lid margins, under the lids (i.e. it’s the part that lines the eyelids)
What 3 regions is the palpebral conjunctiva divided into?
Marginal region
Tarsal region
Orbital region
What is the forniceal conjunctiva composed of and where is it found?
loose, redundant tissue in the fornix (form the junction between the palpebral and bulbar conjunctiva)
Where is the bulbar conjunctiva found?
is continuous with the corneal epithelium at the limbus
What is”Palisades of Vogt” and where is this found?
Corneal stem cell reservoir. Found at the limbus (appearing as radial ridges)
When is the bulbar conjunctiva not attached to Tenon’s?
At the limbus, where the two layers fuse
How tightly attached is the bulbar conjunctiva to Tenon’s?
Loosely
Describe the structure of the palpebral conjunctival epithelium (2)
Non-keratinised, stratified squamous epithelium (similar to cornea)
How can we distinguish the conjunctival epithelium from the corneal epithelium?
via the expression of different cytokeratins, mucins, and by the presence of glycocalix
Describe the structure of the bullbar conjunctival epithelium? (2)
Stratified columnar epithelium
(so, from this and palpebral, we know that the structure of the epithelium changes depending on which part of the conjunctiva we are at. sourced from science direct: anatomy of the eye and orbit)
Describe the epithelial cellular composition of the conjunctival epithelium, in terms of: Depth of epithelium (1), types (3), description (2)
The epithelium is composed of epithelial cells about 5-8 cells deep. These epithelial cells are organised into 3 main types: basal, intermediate, and superficial.
The basal cells at the deepest part of the epithelium are cuboidal, and as these cells go up to the surface, they become flatter to be polyhedral cells and then finally squamous cells (at the surface)
Define squamous
A layer of epithelium consisting of very thin flattened cells. [known as squamous cells]
Aside from epithelial cells, what other cells can be found within the conjunctival epithelium?
Goblet Cells
Melanocytes (melanin forming cell: amount depends on race)
MHC II +ve Dendritic Cells
Intraepithelial Lymphocytes
(source: science direct - anatomy of the eye and orbit)
What is the role of goblet cells in the conjunctiva?
secrete mucus (protective function)
What is the function of intraepithelial MHC II +ve Dendritic Cells? (source: science direct - anatomy of the eye and orbit)
function as “sentinels” on the ocular surface and are responsible for trapping and internalising antigens and transporting these signals to either local lymph nodes (such as pre-auricular node) or conjunctival associated lymphoid tissue (CALT) or follicles – where they are capable of presenting antigens to naive T cells and induce primary immune responses, or driving antigen specific B cell maturation and immunoglobulin prodcution
Are lymphocytes present in normal conjunctival epithelium?
Yes. However they get more dense upon inflammatory conditions
Does the conjunctival epithelium have any blood vessels?
no
Describe the structure of the substantia propria (stroma) of the conjunctiva (2)
Highly vascularised, loose, connective tissue
Aside from connective tissue, name the components of the substantia propria of the conjunctiva (3)
CALT
Some fibroblasts
Immune Cells
If you see an inflammatory response in somebody’s eye that is going away from the limbus, what is the condition typically responsible for this?
Conjunctivitis
What is Ocular Surface Squamous Neoplasia (OSSN)?
a spectrum of diseases involving abnormal growth of dysplastic squamous epithelial cells on the surface of the eye
Name 2 types of OSSN
Papilloma
Conjunctival Intra-epithelial neoplasia (CIN)
What is the main difference between papillomas and CIN? (1)
CIN invades the corneal squamous epithelium, papillomas do not
If CIN invades the corneal squamous epithelium, why is it only considered “pre-malignant”?
Because while it invades this, it doesn’t invade the substantia propria, so it’s invasion is restrained (restrained invasion)
What part of the conjunctiva or cornea is involved with papillomas
involves conjunctival squamous epithelium
remember: papillomas do NOT involve the cornea
Can CIN lead to malignancy?
Yes. Small chance. Do a surgical removal if this happens
What is the difference between Squamous Cell Neoplasia (SCN) and Conjunctival Intra-epithelial neoplasia (CIN)?
SCN invades BOTH the cornea and the substantia propria (whereas CIN only invades corneal squamous epithelium)
What type of neoplasia is squamous cell neoplasia (SCN) classified as?
Malignant conjunctival neoplasia
Describe how the conjunctival epithelium looks histologically in a patient with conjunctival papilloma (4)
conjunctival epithelium is fatter and overgrown, but is homogenous and is non-invasive into surrounding tissues so the basement membrane remains intact (so no invasion of stroma)
What indicators can we use to differentiate a papilloma from malignancy? (4)
Lesser red colour (pinkish from distance)
Non-invasive of cornea
Motile (i.e. easy to move with cotton bud)
Fewer feeder blood vessels
What do spots on a conjunctival papilloma indicate? (2)
Either malignancy possibly or strawberry birth mark
What does the conjunctival epithelium look like histologically in a patient with CIN? (4)
Metaplasia and pleomorphism of the local conjunctival squamous epithelium. Cells can also become keratinised. Still no invasion of stroma (basement membrane intact)
How can we differentiate CIN from papillomas as optometrists?
Compared to papilloma:
- Conj looks redder
- More feeder vessels
What is the chance of malignancy if CIN remains untreated?
High
In terms of clinic procedures, how does CIN differ from malignancy? (3)
Motility (easy to move with cotton bud)
OCT - definitive tool
Surgery for biopsy and management of pre-malignant state
Name one indicator found in OCT that can differentiate malignant from non-malignant CIN
Keratinisation - an expression of malignancy. Appears as a white plaque
What happens when CIN progresses to SCN?
The CIN breaks through the basement membrane and invades the underlying substantia propria (stroma)
Is SCN motile/able to be moved by cotton bud?
Nope. Because it’s anchored by the stromal invasion
How would ulceration appear as in SCN patients?
White plaques
Can SCN cause haemorrhages?
Yep. Can cause small haemorrhages
How can we differentially diagnose that it’s SCN not CIN? (1)
OCT
