epithelia Flashcards
what are the 4 basic tissue types of organs
epithelium
connective tissue
muscle
nervous tissue
what are epithelia composed of
closely aggregated, polyhedral epithelial cells with a minimum of intercellular substance
adhesion between epithelial cells is
A. strong
B. weak
A. strong
thus cellular sheets are formed which are able to cover exposed external surfaces and line internal cavities
what does the epithelial form
the outer protective layer of the skin
epithelia are usually polarized
yes
all epithelial cells have a sheet like structure composed of extracellular matrix components called what
basal lamina (basement membrane)
epithelial cells are described as non vascular, what does this mean
nutrients from capillaries in underlying tissue must diffuse across the basal lamina
epithelial cells tend to bind together in what form
sheets
what are some functions of the epithelia
mechanical barrier (skin) chemical barrier (lining of stomach) absorption (lining of intestine) secretion (salivary gland) containment (lining of urinary bladder) locomotion (by cilia - oviduct)
the role ofthe epithelium determines its what
type and structure
two types of cellular components that are vital to the function of epithelia in the care
- cytoskeleton (maintains cellular integrity)
- intercellular junctions(links cells together into a functional unit)
what are the three main classes of filaments that form the cytoskeleton of cells
microfilaments
intermediate filaments
microtubules
what is the diameter of the microfilament
5nm
what is the diameter of the intermediate filament
10nm
what is the diameter of microtubules
25
how do filaments become attached to cell membranes and to each other and what does this form
by anchoring and joining proteins to form a dynamic 3 - dimensional internal scaffolding in the cell
the fine strands of what protein make up microfilaments
actin
what are the functions of microfilaments
anchorage, movement and extension of cell membrane
under which structural feature are actin filaments located
cell membrane
in microfilaments, what does globular actin polymerize to form
filamentous actin
what do intermediate filaments bind together
bind intracellular elements and then binds this to the plasmalemma
intermediate filaments are not as dynamic as what
microfilaments and microtubules
what two subunits are microtubules composed of
alpha and beta in an alternating array
microtubules can be described as
assembled and disassembled
what are microtubules important in
movements of components in the cell and in cell division (from the spindle apparatus)
intercellular junctions are specialised structures which link what
individual cells together into a functional unit
what are the 3 types of intercellular junctions
occluding junctions
anchoring junctions
communicating junctions
what’s the role of an occluding junction
links cells to form a diffusion barrier
what’s the role of an anchoring junction
provides mechanical strength
what’s the role of a communicating junction
allows movement of molecules between cells
what effect does an occluding junction have on diffusion
it inhibits diffusion
occluding junctions appear as a focal region of close apposition between what
adjacent cell membranes
in occluding junctions, what is another name for a tight junction
zonula occludens
in an anchoring junction, what is the role of an adherent junction
links submembrane actin bundles of adjacent cells
what is another name for adherent junctions
zonula adherens
what transmembrane molecule bind to eachother in the extracellular space, and, through link molecules, to actin of the cytoskeleton
cadherin
what do desmosomes link and what is the name of the function
links submembrane intermediate filaments of adjacent cells
called macula adherens
what role do desmosomes provide in the skin
provide mechanical stability
what do communicatice junctions allow
selective diffusion of small molecules and ions between adjacent cells
where are communicative junctions found
epithelia
smooth muscle
cardiac muscle
what is a junctional complex
close association of several types of junctions found in certain epithelial tissues
covering epithelia are based on what
cell shape
the number of layers of cells
cell surface, tissue surface, specializations
presence of any specialized cell types
if a cell were to be described as A. squamous B. cuboidal C. columnar, what would this be describing
A. flattened, like a fish scale
B. cube shaped
C. like a column, tall and thin
if a cell were to be described as A. simple B. stratified C. pseudostratified, what would this be describing
A. one layer
B. two or more layers
C. tissue appears to have multiple layers, but in fact all cells are in contact with the basal lamina
what are some specializations of cell surface or tissue surface
- prominent microvilli
- cilia
- kertinized (presence of layers of keratin proteins on the tissue surface)
what are goblet cells
single cell mucous glands
what is the role of microvili in epithelia
serves to increase the surface area of the cell membrane
what are the length of microvili
0.5-1um
how long are motile cells
10um long
what is the purpose of motile cells
serve to propel mucous or fluid over the cell surface
what structures can be seen within cilia
core of microtubules
what are keratins
groups of tough structural proteins
