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)