Epithelium Flashcards
4 basic tissue types
epithelium
connective
muscle
nerve
What do basic tissues contain?
cells and ECM
Define
Cell
basic structural and functional unit of all multicellular organisms
Define
Tissue
organized aggregation of cells that function in a collective manner
Define
Organ
differentiated structure consisting of cells and tissues and performing some specific function in an organism
What are the 8 organ systems of the body?
circulatory
lymphoid
respiratory
digestive
endocrine
urinary
reproductive
integumentary (skin)
Define
parenchyma
cells responsible for an organ’s specific functions
Define
stroma
cells that have a supporting role in an organ
Epithelial Tissue
vascular or avascular
avascular
no blood vessels
Epithelial Tissue
location
lining all external and internal surfaces of the body
any substance entering or exiting the body must cross some type of ____
epithelial tissue
the ____ surface is attached to an underlying ____ ____
basal; basement membrane
cell size and morphology are determined by ____
their function
epithelial tissue
functions
- protection
- absorption
- secretion
Define
basal pole
part of the cell contacting the ECM and connective tissue
Define
apical pole
the opposite end, usually facing a free surface (open space)
some ep. cells have specialized apical surface mods depending on func’n
Define
basement membrane
noncellular, thin extracellular sheet of macromolecules, forming a semipermeable filter for substances reaching the epithelial cells from below
name
2 regions of basement membrane
- basal lamina
- reticular lamina
Define
basal lamina
thicker electron-dense part closer to epithelial cell
(typically used synonymously with basement membrane)
Define
reticular lamina
more diffuse and fibrous (reticular fibers) which joins with the underlying connective tissues
Define
microvilli
apical cytoplasmic projections
microvilli
Function
increase surface area for absorption
microvilli
location
- prominently found in digestive tract to absorb nutrients
- densely packed; brush border projecting into lumen
What is a brush border
appearance of microvilli under a microscope as a striated border projecting into lumen
number of microvili on the surface of a cell
can be 100-1000s
microvilli
composition
contain bundled actin filaments capped by the plasma (cell) membrane
Define
terminal web
horizontal network of actin filaments and intermediate filaments below the base of the microvilli
microvilli
actin filaments (microfilaments) insert into the ____
terminal web
microvilli
motile/nonmotile
nonmotile
Name
specialized apical cell surface modifications
- microvilli
- sterocilia
- cilia
Define
stereocilia
long microvilli
Stereocilia
location
- mostly limited to male reproductive tract
- sensory hair cells of inner ear
stereocilia
function
increase cell surface area to facilitate absorption; mechanoreceptors in hair cells of ear
stereocilia
composition
microfilaments (a core of actin filaments) anchoring to terminal web
stereocilia
motile/nonmotile
nonmotile
Define
cilia
long apical structures, larger than microvilli (longer and wider)
cilia
composition
contain internal arrays of microtubules (not microfilaments):
axoneme and basal bodies
Define
axoneme
organized core of microtubules arranged in a 9+2 pattern
9 outer doublets, 2 central
Located in cilia
Define
basal bodies
outer 9 paired microtubules join the basal body below the cell membrane anchoring the structure to the cytoskeleton
a modified centriole
cilia
motile/nonmotile
motile
capable of moving fluid and particles along epithelial surfaces
What 2 factors is traditional classification of epithelium based on?
- number of cells (layers of cells)
- shape of cells
classification of epithelium
number of cells
- simple epithelium - one cell layer thick
- stratified epithelium - 2+ layers
classification of epithelium
shape of cells
- squamous - cell width>height (thin flat cells)
- cuboidal - width=depth=height
- columnar - height»width
epithelium
2 special/other classifications
- pseudostratified
- transitional (urothelium)
Define
pseudostratified
- appear stratified
- columnar; nuclei appear at different levels
- some cells may not reach free surface
- all cells rest on basement membrane
pseudostratified=simple epithelium
transitional epithelium (urothelium)
- location
- shape
- function
epithelium lining found in the lower urinary tract
- always stratified
- dome-like cells (umbrella cells); unique morphologic features that stretch, allowing for distention which alters/transitions cell shape
function
terminal web
anchor microvilli
When classifying stratified epithelium, only consider…
only consider the shape of the apical layer (and surface modifications)
shape and height of cells vary from layer to layer
2 specialized classifications of simple squamous epithelium (based on location)
Endothelium
Mesothelium
simple squamous epithelium lining the surface of blood & lymphatic vessels?
endothelium
simple squamous epithelium lining the walls and covers serosal surfaces of closed cavities of the body
mesothelium
what is serosal surface
free outer surface
what type of epithelium covers the outer wall of the intestine?
mesothelium
what special surface modification is on the lining of the oviduct?
cilia
where is keratin located?
dry surfaces
what type of epithelium is always stratified?
transitional (urotherlium)
where is urothelium found?
transitional epithelium
urinary bladder
what type of epithelium is always collumnar?
pseudostratified
function
goblet cells
secrete lubricating mucus
Define
secretory epithelia
epithelial cells that function to produce and secrete various macromolecules and comprise glands
what type of epithelium are glands made of?
secretory epithelia
exocrine glands secrete products via…
secrete products through epithelial ducts connected to a surface
What do endocrine glands lack? How do they secrete their products?
lack a duct system; direct secretion into surrounding connective tissues where capillaries absorb secreted products
secretions of endocrine glands are called ____
hormones
exocrine glands can be ____ or ____
simple or compound
simple exocrine glands
ducts not branched
compound exocrine glands
ducts with 2+ branches
exocrine secretory portions can be ____ or ____
tubular or acinar
tubular exocrine gland secretory portions
short, or long and coiled
acinar exocrine secretory portions
rounded and sac-like
3 exocrine gland release mechanisms
- merocrine secretion (eccrine)
- holocrine secretion
- apocrine secretion
define
merocrine secretion
eccrine
- secretory product is released in membrane-bound vesicles to the apical surface of the cell
- extrude contents by exocytosis
define
holocrine secretion
cells accumulate product as they mature and enlarge, ending in rupture of cell and release of products
define
apocrine secretion
product accumulates in cell apical surface, released along with a thin layer of cytoplasm within an evelope of plasma membrane
3 types of secretory products
- mucous
- serous
- seromucous
define
mucous secretions
viscous and slimy; contain heavily glycosylated proteins
define
serous secretions
watery; high in unglycosylated proteins
define
seromucous secretion
mix of serous and mucous secretions
what does ‘labile’ mean
ability of epithelial cells to renew continuously by mitotic activity and stem cell populations
in stratified epithelium, where do stem cells and mitosis occur?
only in the basal layer
what is the most common mechanism of exocrine gland secretion?
merocrine
