Apr9 M2,3-Histology of Skin Parts 1 and 2 Flashcards
skin type of epithelium
stratified squamous keratinized epithelium
keratinization def
- killing of cells by massive cross linking of cytoskeletal proteins and other proteins in the cell
- the cell dies
metaplasia def
- deviation from normal in epithelia
- can result in tumor cell migration or metastatic cells (skin cells are doing displacement, not migration, as they mature to the surface)
keratins = what kind of protein
keratins = gene family that is part of the intermediate filaments category (that make the cytoskeleton)
equivalent of epidermis and dermis in the mouth
epithelium and LP
together, form the mucosa
hypodermis content
layer of adipocytes
(IMPORTANT) layers of the epidermis (base to top)
- stratum basale or germinativum
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
epidermis and dermis interactions and significance
- interdigitate between each other
- epith protrusions in dermis = rete pegs
- dermis protrusion in epith = dermal papillae
- allows better exchange with lymphatics and caps
- gives fingerprints
stratum granulosum charact + next step
- cells have granules
- will do massive cross-linking and change their cytoskeleton to form the next layer
- will form stratum lucidum
melanocytes location in the skin + start what cancer
- epidermis
- along the stratum germinativum (basale)
- send processes that insert between the cells
- start melanomas
2 main proteins in dermis + 2 layers of the dermis
- collagen and elastin
- papillary (closest to BM) and reticular
dermis papillary layer (closest to the epidermis, BM) content and reticular layer content
- papillary = small type 3 collagen fibrils (reticular fibers)
- reticular = type 1 collagen
BM charact
- EC matrix with collagen, elastic tissue
- porous supporting plane + solid attachments
- serves as attachment point for cells
how basal cells attach to the BM + name of the attachment
- use a R on their surface called an integrin
- binds ligand in BM matrix
- HEMIDESMOSOME
desmosome fct and contents
- cell-cell connection
- EXTERIOR = CADHERINS of each cell for attachment (cadherin-cadherin)
- INTERIOR = cadherins attached to plasma membrane and to a circular structure under the membrane.
- cytoskeletal elements (interm filaments and keratin) attach to circular structure
charact of cells in stratum spinosum
send protrusions
diff proteins in the papillary layer (right under BM)
- type 3 collagen (reticular fibers)
- type 7 collagen (forming velcro loops)
- elastic fibers (elastins)
- collagen IV (type 4)
- laminins
tonofilaments def and location
- cytoskeleton expressed from particular keratinocyte genes and that cross-links and forms fibrils
- are the keratins of the intermediate filaments that attach on the cytoplasmic circular structure in hemidesmosomes or desmosomes
most important protein the skin expresses
keratin (to make a solid barrier + involved with lipids)
2 major families (names) of the cadherins of the epidermis (for desmosomes, cell-cell)
- desmogelins
- desmocolins
charact of the space between the cells formed by a desmosome
- water impermeable glycolipid deposition place
- specific lipids secreted there
- these lipids assemble in lamellated granules (discs)
cell-cell interaction general rules in the whole body
- 2 integrins on same cell form cis-dimer
- 2 cis-dimers from 2 diff cells interact together IF ARE OF THE SAME KIND
- interaction is CALCIUM DEPENDENT
how cadherins interact in the epidermis vs in the rest of the body
- rest of the body = expressed all around the cell
- epidermis = form specific regions called desmosomes
charact of the granules in the stratum granulosum
- called keratohyalin granules
- NOT membrane bound
- are an accumulate of proteins around tonofilament
major protein in the keratohyalin granules of stratum granulosum
filaggrin
how cytoskeleton and keratohyaline granules start cross-linking in stratum granulosum
transglutaminases are enzymes that make irreversible covalent bonds between them
important thing that must happen for the skin to slough off + consequence of genetic disease in that
- desmosomes must detach
- defect = bacterial infections
stratum lucidum charact
- in thick skin (sole of feet and palms)
- are a massive-cross-linking
- cells there are DEAD
name of the cells in the stratum lucidum
squames (skin sloughin off = cell desquamation)
2 proteins other than keratin known to be part of the stratum corneum enveloppe and to cross-link also
- loricrin
- involucrin
epidermolysis bullosa def
- blistering disease of the skin in response to minor trauma
- bc of an adhesion disease of the skin, skin not tough enough. shearing. mechanical tears
basal cell vs squamous cell CA
- basal cell CA of the skin = starts in stratum basale cells
- squamous cell CA of the skin = starts in stratum spinosum (higher layer)
- squamous more dangerous*
adenoCA of the skin def
CA starting in epithelium of the glands
what determines ability to heal after a burn
- how deep
- how wide
- important for determining if you destroyed stratum basale cells and how much bc are important for regen*
warts def
- circular ingoing benign infection with HPV
- perturbation of the process of cross-linking
- scaly lesion
blisters def
mechanical separation of the skin
psoriasis def
itchy patches. immune disease of T cells activation where they prolif too much
epidermolysis bullosa on histology
- massive bleeding and hemorrhage
- skin sliding above BM
- ripped, cracked epidermis
ichtyosis def
- mutations in intermediate filaments (Interm - Ichtyosis. i-i) OR filaggrin OR transglutaminase mutations
- problem of keratinization process
melanocytes function
- make melanin granules, which protects DNA from UV light by ABSORBING UV light
- granules are placed between the nucleus and the outer surface of the skin (to protect from UV light)
how melanin is produced
- golgi involved
- tyrosinase is produced (enzyme) and is packed in vesicles
- tyrosin vesicles are also formed
- the two premelanosome vesicles fuse forming a melanosome
- tyrosinase converts tyrosin to melanin to form a melanin granule (melanosome)
how melanin granules protect keratinocytes if they’re only produced by melanocytes
- melanocytes projections between keratinocytes
- melanocytes release their granules outside of the cell
- granules are engulfed by cells of the stratum spinosum
- melanosomes moved above nucleus
embryologic origin of melanocytes
neural crest cells (NCCs)
difference in melanocytes cell-cell attachment
doesn’t do desmosomal connections with keratinocytes
albinism cause + thing to be careful about in this disease
- mutation in tyrosinase gene (partial or complete)
- higher risk of skin cancer
abundant cell type in the dermis and that is also the ‘‘grandfather’’ of all cells
fibroblasts (or fibrocytes)
function of fibroblasts
- make type 1 collagen (reticular dermis)
- make type 3 collagen (reticular fibers in papillary dermis)
- make type 7 collagen loops for papillary dermis
- etc
cell that fibroblasts originate from and what other cells can this ancestor give rise to
undifferentiated mesenchymal stem cell. can give
- fibroblast
- adipocytes
- macrophage, histiocyte
- mast cell
- plasma cell
name of components of collagen
- collagen fibrils (=seen on EM)
- many fibrils from collagen fibers (seen on LM)
structure of the collagen molecule
- 3 protein chains forming a triple helix (collagen tropomolecules)
- released in exocytic pathway
- self polymerize to form fibrils
time to make collagen and why
60 mins
- post translational modifications (PTMs)
- must form triple helix
- exists in pro-granules initially
what cells make AND turn over collagen
fibroblasts
how fibroblasts turn over collagen
with enzymes like collagenases and MMPs
bone structure
- collagen matrix
- calcium phosphate crystals bind on the matrix
- cracks on the surface and banding pattern
- osteoclasts and osteoblasts
structure of teeth enamel and dentin and pulp (EM)
- enamel = exterior = dead
- dentin = odontoblasts, cell processes and nerves going through holes occupied by odontoblasts
- pulp = matrix of EC collagen
important molecule in collagen synthesis
- vitamin C
- important cofactor in collagen triple helix assembly in the cell
examples of diseases if you lack vit C, Ca or copper (most visible signs you get)
get a collagen deficiency
- teeth falling out bc held to jaw by periodontal (suspensory) ligament
- knees faling out (defective ACL)
how collagen fibrils cross-link
lysyl oxidase protein does that
2 main components of the ECM
- fibers (collagen, reticular fibers, elastic fibers)
2. amorphous ground substance (proteoglycans, plasma proteins, etc.)
function of proteoglycans
- resistance to compression
- water retention
components of elastin fibers
- elastin protein
- fibrilin protein (forming microfibrils)
elastin fibers found where and consequence of mutation
- skin, lungs, blood vessels*, etc.
- can get aneurysms, stroke
Marfan syndrome charact
- fibrillin-1 gene mutation so problem in the microfibrils of elastin fibers
- ectopia lentis (displacement of eyes lenses)
