Epithelial Tissue Flashcards
where can epithelia be found
body surfaces, lines body cavities and forms glands
what do epithelial cells produce
keratin intermediate filaments
what are keratin intermediate filaments useful for
tumor ID
where is the epithelia derived from
ecotoderm, endoderm or mesoderm
what parts of the epithelia are derived from the ectoderm
-epidermis (hair nails, glands, mammary glands; oral and anal mucosa
- cornea and lens of eye
-enamel organ and enamel of teeth
-anterior pituitary
-inner ear
what parts of the epithelia are derived from the neuroectoderm
-neural tube (CNS)
- pineal body, posterior pituitary, sensory epithelium of eye, ear and nose
- neural crest (PNS)
- ganglia, nerves, glial cells, adrenal medulla, melanocytes, neuroendocrine cells
what part os epithelia arise from the mesoderm
epithelium of kidneys and gonads
- mesothelium (lining pleura, peritoneal and pericardial cavities)
- endothelium (blood and lymph vessels)
-adrenal cortex
what part of epithelia is derived from endoderm
- respiratory epithelium
-alimentary epithelium (except oral and anal cavity) - liver, pancreas, gallbladder, thyroid, parathyroid, and thymus
- epithelial lining of tympanic cavity and eustacian tubes
- transitional epithelium of bladder
what are the functions of the epithelium
-barrier (skin)
- SPM
- Secretion
- absorption
- transport
-sensation
is epithhelia penetrated by blood vessels
never
what supports epithelia
basement membrane
what does the basement membrane do
separates epithelium from underlying connective tissue and blood vessels
what do epithelial cells rely on to survive
diffusion of O2 and nutrients from underlying tissue
what makes up the mucous membrane
epithelium that lines cavities that connect with outside world such as alimentary, respiratory, or urogenital tracts)
what makes up the muscularis mucosae
surface epithelium of ectoderm, basement membrane, supporting connective tissue (lamina propria), and layers of smooth muscle
what are the 3 layers of the basement membrane
lamina densa, lamina lucida, and lamina reticularis
describe the lamina lucida
most superficial, in contact with basal cell membrane
describe the lamina reticularis
most deep, merges with surrounding tissue
describe the lamina densa
anchored to underlying connective tissue by microfibrils of type 4 collagen
what are cell junctions
intercellular epithelial attachment sites
what are the types of cell junctions
occluding, adhering, communication
what is another word for occluding junctions
tight junctions
where are occluding junctions located
immediately beneath luminal surfaces of simple columnar epithelia
what are zona occludens
portions of opposing cell membranes that fuse together forming continuous cicumferential band around cells in occluding junctions
what do occluding junctions do
prevent leakage between cells by sealing intracellular spaces
where is the fascia occludens
between endothelial cells in wall of blood vessels
whats another term for adhering junctions
anchoring junctions
what do adhering junctions do
bind cells together, act as anchoring points for cell cytoskeleton
what is the zonular adherens
a continuous band characterized by transmembrane glycoproteins called cadherins
do cell membranes fuse in adhering junctions
no
what are macula adherens
small, circular patches; most common type of cell junctions
where are adhering junctions located
on the lateral surface of the cell
what attachment proteins are found in adhering junctions
desmoplakins, desmogleins, and tonofilaments
where are hemidesmosomes found
on basal surface of cell only, anchoring it to basement membrane via integrins
what type of cell junction are hemidesmosomes
adhering junctions
what type of cell junction is associated with high mechanical abrasion
hemidesmosomes
what is a junctional complex
hybrid of adhering junctions and occluding junctions
what are the zones in a junctional complex
zonula occludens, zonula adherens, macula adherens
what is another term for junctional complex
terminal bar
what is another word for zonula occludens
tight junction
what is another word for zonula adherens
adherent junction
what is another word for macula adherens
desmosomes
what is another word for communicating junctions
gap junctions
where are gap junctions located
focal or regional adherent zones located on lateral border of cell
describe gap junctions
roughly circular, intercellular contact areas containing hundreds of individual channels called connexons
what are connexons made of
a ring of 6 integral proteins
what do gap junctions do
permit passage of small molecules between adjacent cells, allow transport of information and metabolites between cells
what are microvilli
finger like cytoplasmic projections that extend from the cell surface
what are microvilli made of
actin filaments
what is the function of microvilli
increase SA for absorption or secretion
where can microvilli be found
striated border in intestine and brush border in renal tubules
what supports the microvilli and what is it made of
the terminal web which is made of actin microfilaments at base
what are sterocilia
long microvilli, not cilia
where are stereocilia found
in epididymis of males and sensory cells of inner ear
are sterocillia motile
no
what do stereocilia contain
actin filaments
what are cilia
long, motile cytoplasmic extensions
what is an axoneme
“9 + 2” arrangement of microtubules
where can an axoneme be found
cilia
where do cilia arise from
individual basal body
what do cilia develop from
centrioles
how do cilia move
they beat in synchronous metachronal rhythm which is a rapid effective stroke followed by a slower, flexible recovery stroke
why are cilia unevenly spaced
to perform metachronal rhythm
what do cilia contain
microtubule doublets with dynein arms
what disorders arise from microtubules lack of dynein arms in cilia
kartageners syndrome, dextrocardia or sinus inversus, and hydrocephalus
what is kartageners syndrome
causes sterility in males due to non functional flagella on sperm
what is dextrocardia/sinus invertus
heart and/or other organs moved from left to right due to absence of ciliary activity during embryonic development
what is hydrocephalus
due to non functional cilia on ependymal cells unable to circulate CSF. results in enlargement of the head
what are the 3 criteria for epithelial classification
-number of cell layers
- shape of cells
-surface specializations
describe simple epithelial layers
1 cell layer thick
describe stratified epithelial layer
2 or more cell layers
describe pseudostratified cell layers in epithelia
looks stratified but isnt, all cells rest of basement membrane but not all cells extend to epithelial surface
describe squamous cells in shape
flattened, width is greater than height
describe cuboidal cells in shape
width is about equal to height and depth
describe columnar cells in shape
height is greater than width
describe simple squamous cells
one cell thick
describe simple cuboidal cells
1 layer thick, look like cubes
describe simple columnar cells
single layer, tall, nuclei often cluster along base of the cell
describe stratified squamous cells
-more than 1 layer thick
- cells near the surface are flattened, cells near the base are different shapes
why are cells lighter pink and have no nucleus towards the surface in stratified squamous cells
they are dead
describe pseudostratified epithelial cells
- all cells are in contact with the basement membrane
- only 1 cell layer thick
-cells are different sizes and shapes
where would you find pseudostratified epithelia
respiratory cells
describe transitional epithelia
-stratified epithelium modified for distensibility
- varies from sqaumous to cuboidal
where can transitional epithelia be found
lines most of urinary tract except for parts of urethra
describe endothelium epithelia
simple squamous
where is endothelium epithelia found
lines blood vessels and lymphatics
where is mesothelium found
lines closed body cavities such as pericardial and abdominal cavities
describe mesothelium
simple squamous although they can look thicker almost like cuboital
what are glands made of
epithelial cells
how do you classify glands
-morphology of the gland/duct
- type of secretory produce
- mode of discharge of secretory product
what are the 2 types of duct morphology
simple gland and compound gland
what is a simple gland
unbranched ducts (straight or coiled)
what is a compound gland
branched ducts
what shapes can glands be
-tubular
-acinar
-tubuloacinar
describe tubular glands
tube like (straight or coiled)
describe acinar glands
sac like or flask shaped, individual sacs called acinus
what are tubuloacinar glands
intermediate tube with dilated end
describe serous glands and give example and stain color
watery, bascophili acini
ex: parotid gland
stains dark purple
describe mucous gland and give example and stain color
thick viscous secretion of proteins
ex: palatal
stains pale and looks foamy
what are mixed glands
contain mucous and serous acini and serous demilunes
what do sebaceous glands secrete and where can they be found
glands of skin secrete lipids in form of sebum
what do ceruminous glands secrete and where are they found
secrete cerumen (ear wax) and found in external ear canal
what are the two functional groups of glands
endocrine glands and exocrine glands
describe endocrine glands
lack ducts, secrete hormones into bloodstream
describe exocrine glands
secrete product onto epithelial surface via ducts
what type of cells do exocrine glands contain
myoepithelial cells
what are myoepithelial cells and where can they be found
specialized contractile cells that assist in secretion that lie between secretory cells and basement membrane
what are goblet cells
specialized unicellular exocrine glands located in epithelium that secrete mucus
what are the modes of discharge
merocrine, apocrine, and holocrine
describe merocrine glands
also called eccrine glands, only secretory product release is proteins,most common, invovles simple exocytosis
where can merocrine type glands be found
sweat glands on skin
describe apocrine glands
secrete membrane bound vesicles, product accompanies by some cytoplasm but usually lipid and protein products
where can apocrine glands be found
apocrine sweat glands and mammary glands
describe holocrine glands
entire cell secreted, products are so thick that the cell must rupture to release its products
where can holocrine glands be found
sebaceous glands
