Epithelial tissues and cell interactions Flashcards
What is the difference between exocrine and endocrine gland
- exocrine: secrete prodicct on body surface or body tube
- endocrine: secrete product directly into BS
Examples of exocrine and endocrine glands
EX: Intestinal gland (mucus released on GI tract lumen), Sebaceous gland (secretes sebum on skin surface)
END: pituitary gland (secrete hormone in blood capillaries)
What are tight junctions
Junction between apical surface and basal surface (stops macromolecules and proteins from getting from BS to AP)
What does laminin do and features
consists of 3 chains (a,b,y)
- contains 2 collagen and 1 cell binding (a) domains
- helps epithelial attach to basement membrane
Where is basement membranes found
- between epithelial cell and connective tissue
- endothelial lining of capilaries
What do connective tissues contain
- fibroblasts
- adipocytes
- mast cells and macrophages
- collagen and elastin
- cytoplasm – extracellular matrix
What do extracellular matrix consist of
groud substance- water loving proteoglycans (resists compressive forces) that trap water
- ground substance and fibres
-
What are proteoglycans and aggrecans
-P consists GAG (glycoamino glycan)– disaccharide units– attract sodium with negative sugars– attract water – viscours– resist compressive forces
AG– 3000 serine rich core protein, 100 chrondroitin sulfate and 30 keratin sulfate, that GAG is attached to
How are collagin tissues made
collagen alpha chain- synthesised in fibroblast cytoplasm– diffuse in ER– form triple helix (SV)– exotysosis – triple helix into fibril– collagen fibre
How are elastin made
Tropoplastin – collagen alpha chain- synthesised in fibroblast cytoplasm– diffuse in ER– exocytosis– elastin– fibrillin +elastin– elastin fibre
What are the most important cell types in the epidermis
keratinocytes >90%
- found in basal cell layer
- specialised and can divide into new stem cells
How are cells in the epidermis renewed
-kerotinocytes stop dividing- detatch from basement membrane – migrate through epidermis layers – terminal differentiation—->nuclear degradation , aggregation, lamellar bodies, lipid excrusion
What is a cornified envelope
- tough insoluble sack below plasma membrane of keratinocytes – final stage of terminal differentiation
What is the stratum corneum
- flat anuclear keratinocytes
- epidermal permeability (prevent water loss, protects against microbial invasion)
- hard for drugs to go through stratum corneum (transappendageal, transepidermal routes)
What are the main stress bearing components in epithelial cells and connective tissues
Connective tissues– extracellular matrix
epithelial cell– cell cytoskeleton linked by cell-cell and cell-matrix junctions
What are components of cell-cell and cell- extracellular matrix junctions
tight junctions (fence -prevents proteins from apical to BL and barrier- prevents protein from diffusing beween cells)
- adherans and desmosomes- cell adhesion
- gap junctions - cell communication to one cell to another
HEMODESMOSOMES AND DESMOSOMES–link cell to basal membrane (adhesion) AND LINK TO keratin intermediate filaments
FOCAL ADHESIONS AND ADHERANS JUNCTIONS– adhesion: AND LINK TO actin microfilaments
What are the components of the cytoskeleton and what protein are they made up of
IF- maintaining tissue integrety (KERATIN)
Microfilaments- cell migration (ACTIN)
Microtubules- cell devision (TUBULIN)
How do intermediate fibres resist stress
- two keratin protein heterodimers
- resist stress by anchroring cells together (via desmosomes) [cell - cell adhesion]
- anchoring cells to basement membrane (hemidesmosomes) [cell matrix adhesion to basal lamina surface]
- important for tissue integrity
- What is pemphigus
- caused by autoantibodies – target adhesion properties of -stops desmogleins from interacting with eachother
- loss of cell-cell adhesion – loss of epidermal integrety– leads to skin blistering
How are actin used in cell migration
- new actin microfilaments formed at leading edge of cell (lamellipodium)
- actin incorporated into Focal adhesions protein – form new focal adhesion– which anchor lamellipodium to substratum (matrix protein)
What are the 3 steps of microfilaments in cell migration
protrusion – actin polymerisation pushes out lamellipodium
ATTATCHMENT- new focal adhesions attatching LP to SUBSTRATUM –creates grip at the front
DETATCHMENT – contraction of actin – tension – relieved when FAs at back are degraded – back moves cell forward
– repeated and move cell for cell migration
How can actin binding drugs potentially be used to treat cancer
- prevents cell motility and dissemination of tumour cells to distance sites
PHALLOIDIN= prevents microfilament depolymerisation
LATRUNCULLIN= prevents microfilament polymerisation
What do microtubules do and what are microtubule binding drugs
- forms the mitotic spindle for cell division
- Taxol prevents microtubule depolymerisation
Vinblastine- prevents microtubule polymerisation
: used as chemotherapy agents (anti mitotic)
– not specific lose hair
What are the features of tight junctions
- prevents paracellular movement (between cells): BARRIER
- maintain epithelial polarity : FENCE
- caludin and occudin (tight junction protein domain)
- also produced by endthelial cell in BBB
