Epithelial Tissues Flashcards
Four Basic Tissues
Epithelium
Connective Tissue
Muscle
Nervous Tissue
Epithelium
Covers body surfaces, lines body cavities, forms glands. Avascular, polarized, mitogenic and densely cellular
Connective Tissue
Underlies and supports the other tissues, includes fibrous CT, cartilage, bone and adipose tissue
Muscle
Contraction, movement
Nervous Tissue
Recieves, transmits, and integrates information to control body activities
T of F Epithelial cells are polarized
True: their plasma membrane differs in composition and function depending upon the cell surface
Epithelia are attached to _____ which separates them from_____
Epithelial cells are attached to the basal lamina which separates the epithelial cells from the underlying connective tissue
Homophillic Interactions
Cell to cell binding with the same thing interacting
i. e. Cadherins binding together via Ca2+
i. e. Ig-Superfamily
Heterophillic Interactions
Cell to cell adhering via different things
Selectins on one cell binding to carbs
Integrins binding to receptor
Cell-cell Adhesion
Zonula Adherens: belt desmosome
wraps around both cells
Desmosome: spot weld (macula adherens)
Cell Matrix Adhesion
Occurs at the basal membrane
Focal Adhesions and Hemidesmosomes
3 molecular components of cell-cell adhesive junctions
Transmemrane Adhesion protein: i.e. cadherin/IgSF
Cytoplasmic Linker protein: i.e. catenin
Cytoskeletal Filament: actin, cytokeratins
Zonula Adherens (3 components)
Transmembrane adhesive proteins: cadherin, nectin
Cytoplasmic linker: beta/ alpha catenin
Cytoskeltal filament: actin
Desmosomes (3 components)
transmembrane: desmogleins/ desmocolins
Cytoplasmic linker: desmoplakin, plakoglobin
Cytoplasmic filament: IF cytoekratins
Hemidesmosomes (3 components)
Attach cell to basal lamina
Transmembrane: integrins/ type 17 collagen
Linkers: plectin
Cytoplasmin filaments: cytokeratins
Focal Adhesions
Form link between actin and extracellular matirx
Transmembrnae: integrins
Cytoplasmin linker: talin, paxillin, vincullin
Cytoskeletal Filaments: actin
Tight Junctions
Restrict diffusion of membrane components (like plastic ring on top of soda cans)
Transmembrane: Claudins, occludins
Linking protein: transcription factors
Cytoskeltal element: Actin
Gap Junctions
Consist of transmembrane proteins (connexins) forming channels (Connexons)
Basal Lamina
Product of epithelial cells
attaches epithelium to underlying CT
Composed of type IV collagen, lamins and proteoglycans
Basolateral Folding
Amplification of surface area
Common in epithelia involved in water/ electrolyte reabsorption
Apical Specializations
Microvilli, Cilia. Keratinization
Microvilli
Increase surface area, core of actin filaments
Cilia
Enclosed by cell membrane, (9+2) microtubules, motility and sensation
Dynein motor protein
Keratinization
Protection, variable thickness, dead cells lost at surface.
Exocrine Glands
Maintain Connection with surface via ducts
Products act locally at surface or lumen
Cells are polarized and porducts are released apically
Endocrine Gland
Lost connection with surface epithelium
Products circulated systemically via vaculature
No obvious polarity
i.e. Pituitary, pancreatic islets, parathyroid
Merocrine
exocytosis
mechanisms of exocrine glands
Apocrine
part of apical cytoplasm lost during secretion
mechanism of exocrine glands
Holcrine
Entire cell degenerates and is secreted
i.e. Sebacious Gland
mechanism of exocrine glands
Myoepithelial Cells
Contractile: properl secretion toward gland opening
Maintain endpiece polarity and architecture
Present in sweat, mammary, salivary and lacrimal glands
Mucous
High molecular weight glycoproteins (mucins)
Serous
Proteins, glycoproteins and enzymes
