Anatomy 9 - Epithelia Flashcards
What is epithelia composed of
Closely aggregated, polyhedral epithelial cells with a minimum of intercellular substance
Adhesion between epithelia is
Strong
What is epithelia able to cover
Exposed external surface and internal cavities
Common features of epithelia
Usually polarised, have a sheet like structure at their basal surface composed of extracellular matrix called the basal lamina, nearly all are non-vascular and they tend to bind together in sheets
Surface epithelia
Cover or line surfaces, cavities and tubes
What are epithelial tissues derived from
All of the embryological germ layers: ectoderm, endoderm and mesoderm
Functions of epithelia
Mechanical barrier, chemical barrier, adsorption, secretion, containment, locomotion by cilia, sensation and contractility
Example of mechanical barrier epithelium
Skin
Example of chemical barrier epithelia
Lining of the stomach
Example of adsorption epithelia
Lining of the intestine
Example of secretion epithelia
Salivary gland
Example of containment epithelia
Lining of urinary bladder
Example of locomotion by cilia epithelia
Oviduct
Example of sensation epithelia
Taste buds
Example of contractile epithelia
Myoephithelial cells
Function of cytoskeleton
To maintain cellular integrity
Three main classes of filaments in the cytoskeleton
Microfilamnets, intermediate filaments and microtubules
What is the function of the filamentous proteins
They become attached to cell membranes and to each other by anchoring and joining proteins to form a dynamic 3D internal scaffolding in the cell
What are microfilaments composed of
The protein actin
Functions of microfilaments
Anchorage, movement and extension of the cell membrane
Function of intermediate filaments
They bind intercellular elements together and to the plasmalemma
What are microtubules made up of
The two tubulin subunits, alpha and beta
Functions of microtubules
Move components of the cell
What are intercellular junctions
Specialised membrane structures which link individual cells together into a functional unit
What are the three types of membrane junctions
Occluding junctions, anchoring junctions and communicating junctions
What are occluding junctions
They link cells to form a diffusion barrier
What are anchoring junctions
They provide mechanical strength
What are communicating junctions
Allow movement of molecules between cells
What is linked together in anchoring junction
Submembrane actin bundles
If the outer layer of adjacent cells appear fused it is known as
A pentalaminar structure
What are desmosomes
They lin k submembrane intermediaries filaments of adjacent cells
What do desmosomes provide
Mechanical stability
What is found in the cell membranes of communicating junction cells
Several hundred pores
What are epithelia classified by
Cell shape, number of layers of cells, cell surface specialisation and the presence of any specialised cell type
What are the different cell shapes
Squamous, cuboidal and columnar
What are the different number of layers of cells called
Simple - one layer
Stratified - two or more layers
Pseudostratified - tissue appears to have multiple layers, but in fact all cells are in contact with the basal lamina
What are the cell surface specialisation categories
Prominent microvilli, cilia and keratinised
What specialised cells can be present in epithelia
Goblet cells
