Histology - Epithelia Flashcards
What are the 4 basic tissue types
Epithelia; connective; muscle; nervous
What is the purpose of surface epithelia
Covers or lines surfaces, cavities and tubes
What are epithelia cells composed of
Closely aggregated, polyhedral epithelial cells with a minimum of intercellular substance
What is the adhesion between cells like
It is strong; thus cellular sheets are formed
What layer of the skin is made up of epithelial cells
The epidermis
What are 3 common features of epithelial cells
Usually polarised; bind together in sheets; non-vascular
Name 3 functions of epithelia
Mechanical barrier (skin); absorption (lining of intestine); locomotion (cilia in oviduct)
Name the 2 types of cellular components that are vital to the function of epithelia
The cytoskeleton; intercellular junctions
Name the 3 classes of filaments that form the cytoskeleton in cells (smallest to biggest)
Microfilaments (5 nm); intermediate filaments (~10 nm); microtubules (25 nm)
What are microfilaments composed of
Fine strands of the protein actin
What are microfilaments’ main functions
Anchorage, movement and extension of the cell membrane
What are intermediate filaments’ main functions
Bind intercellular elements together and to the cell membrane
What are microtubules composed of
2 types of tubulin subunits; alpha and beta
What are microtubules important for
Movement of components in the cell and during cell division
What are intercellular junctions
Specialised membrane structures that link individual cells together into a functional unit
Name the 3 types of junctions found in epithelial cells
Occluding; anchoring; communicating
What are occluding junctions’ main functions
Inhibit diffusion; the focal region of close apposition between adjacent cell membranes
Name the 2 forms of anchoring junctions
Zonunla adherens; desmosomes
Describe how zonula adherens hold cells together
Link tightly onto opposite cells
How do desmosomes hold cells together
Link submembrane intermediate filaments of adjacent cells together
What do communicating junctions (gap junctions) allow between cells
Selective diffusion of small molecules and ions
Describe the structure of each junction
Circular patch studded with several hundred pores
What is an area with close association of several junction types called
A junctional complex
What are the 3 epithelial cell shapes
Squamous; cuboidal; columnar
What is one layer of epithelial cells called
Simple layer
What are several layers of epithelial cells called
Stratified
Describe what pseudostratified is
Appears stratified but all cells contact basal lamina
What are microvilli’s main function and roughly how big are they
Increase the surface area of the cell membrane; 0.5-1 micro metres
What are cilia’s main function and roughly how big are they
Propel mucous or fluid over the cell surface; up to 10 micro metres
What are keratins
Group of tough structural proteins; dead material that accumulates
