Lecture 2 - Basic Tissues and Epithelium Flashcards
what are the four basic tissues that make up all organs and the body?
epithelium, muscle, connective and nerve tissue
what is the function of epithelium?
it creates and maintains distinct compartments: via chemical separation and physical separation
-chemical separation = controls diffusion, selective and directional absorption and secretion
-physical separation = protective barrier
where is epithelial tissue located and what is its appearance?
-covers surfaces, lines cavities and forms tubes
-cohesive sheets of polygonal cells with little intracellular space. there can be multiple layers but they always have one surface (basal) attached to the connective tissue and one free surface (apical) facing air or fluid filled space
purpose of epithelial junctions
- they are a barrier between compartments: polarizes the epithelial layer and facilitates transport
-cell to cell adhesion: aids in barrier and protective functions - cell to cell communication: coordinates functional aspects
-cell to basal lamina adhesion: anchors epithelium to underlying tissue
where are the apical junctional complexes located
typically near the free surface
what is included in the apical junctional complex? what are the key proteins/filament involved
-tight junction = key proteins are occludin and claudin. cell to cell junction
-adherence junction = key protein is cadherin; key filament is actin microfilament
-desmosomes = key protein is cadherin, key filament is intermediate filament
what is involved in the epithelial attachment to the matrix
hemidesmosomes and focal adhesions
what are the epithelial specializations?
microvilli, cilia and interdigitations
microvilli - what does it look like, function? whats in its core?
-finger like projections from apical surface of epithelial cells
-core of actin microfilaments provides support
-non motile - it increases surface area for absorption
cilia - what does it look like, function? whats in its core?
-finger like projections from apical surface of epithelial cells
-core of tubulin microtubules and associated motor proteins
-motile: beating moves material along apical surface or moves fluid in compartment
interdigitations - where are they found, function
-found on lateral and basal surface of epithelium specialized for absorption/transport (like in gut and kidney)
-increase surface area for transport proteins
what are the two major types of epithelia
surface epithelia and glandular epithelia
what is surface epithelia CLASSIFIED by?
-number of cell layers: simple,stratified, pseudostratified (only found with columnar type epithelium)
-cell shape: squamous, cuboidal, columnar, transitional
- surface specializtions: cilia, microvilli, keratin (only in stratified squamous epithelium)
