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Detailed information about various types of epithelia, including simple squamous, simple cuboidal, simple columnar, and stratified squamous, as well as glandular epithelium. It includes examples of each type from different organs and tissues, such as the kidney, thyroid gland, uterine cervix, jejunum, colon, trachea, epididymis, olfactory epithelium, skin, esophagus, parotid gland, urinary bladder, and thick skin. The document also explains the organization and features of each type of epithelium and how it relates to its function.
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-^ Classify^ and^ identify^ the
-^ Explain^ how^ organization
-^ Identify^ and^ describe^ the
NW^ Kidney^ slide^ #151^ –^ Examples^ of^ simple^ squamous
and^ simple^ cuboidal^ epithelium.^ Simple^ squamous
epithelium
of^ Bowman’s^ capsule^ lines^ the^ renal^ corpuscle
(tips^ of^ black^ arrows^ indicate^ the^ nuclei^ of^ simple
squamous^ epithelial cells)^ and^ simple^ cuboidal^ epithelium^ lines^ the
tubules^ (tips^ of^ blue^ arrows).^ Note^ the^ flattened
nuclei^ and^ scant cytoplasm^ of^ the^ squamous^ epithelium.^ In^ the
cuboidal^ epithelium,^ notice^ that^ the^ cells^ are^
about^ as^ tall^ as^ they^ are wide,^ the^ nuclei^ are^ round^ and^ located^ centrally
within^ the^ cell.^ The^ cells^ lining^ the^ tubule^ with
a^ star^ in^ its^ lumen^ is also^ simple^ cuboidal^ to^ low^ columnar,^ although
these^ cells^ are^ more^ irregular^ in^ shape.
NW^ Uterine^ cervix^ slide^ #181^ – Examples^ of^ simple
columnar^ epithelium^ lining^ the^ surface^ of^ the
uterus^ (black
arrow)^ and^ uterine^ glands^ (blue^ arrow).^ Notice
how^ the^ simple^ columnar^ cells^ are^ taller^ than they^ are^ wide^ and the^ nuclei^ are^ elongated^ and^ located^ at^ the^ basal
region^ of^ the^ cells.^ Don’t^ let^ the^ layering^ of^ nuclei
due^ to plane^ of^ section^ fool^ you^ into^ thinking^ this^ is^ a
stratified^ epithelium.^ Remember^ to^ scan^ the^ epithelium
for^ the simplest^ region^ (i.e.^ all^ nuclei^ appear^ to^ be^ in^ one
layer)^ and^ use^ that^ area^ to^ classify^ the^ epithelium.
The^ loose CT^ seen^ here^ is^ highly^ cellular^ and^ contains^ fine
CT^ fibers^ giving^ it^ a^ pale^ pink^ appearance.
NW^ Uterine^ cervix^ slide^ #181^ – Examples^ of^ simple
columnar^ epithelium^ (black^ arrow)^ and^ stratified squamous^ epithelium,^ non‐keratinized^ (blue^ arrow).
Notice^ how^ the^ simple^ columnar^ cells^ lining^ the
uterine cervix^ transitions^ to^ stratified^ squamous^ epithelium.
Many^ layers^ of^ nuclei^ can^ be^ seen^ and^ the^ cells
nearest the^ free^ surface^ are^ squamous^ in^ appearance.
Be^ sure^ to^ zoom^ in^ and^ look^ at^ the^ transition^ at^ higher^ mag.^ Also notice^ the^ highly^ cellular^ loose^ CT^ with^ pale^ eosinophilic CT
fibers.^ What^ tissue^ do^ you^ think^ is^ found^ in^ the
area indicated^ by^ the^ “?”.^ Is^ this^ also^ CT?^ Why^ or^ why
not?
NW^ Jejunum^ #130^ – At^ high^ mag^ note^ the^ presence
of^ the^ brush^ border^ (microvilli)^ on^ surface^ of^ the
simple
columnar^ epithelium^ lining^ the^ intestinal^ villi.^
This^ is^ seen^ as^ a^ discrete^ eosinophilic line^ along
surface^ of^ the epithelium^ (arrows)^ due^ to^ the^ abundance^ of^ actin^ and^ intermediate^ filaments^ in^ the^ terminal
web^ underlying the^ microvilli^ and^ actin^ filaments^ in^ the^ microvilli.
Can^ you^ identify^ the^ apical^ and^ basal^ surfaces
of^ the epithelium^ seen^ here?^ What^ cytological^ features
helped^ you^ determine^ this?
NW^ Colon^ #138 – Example^ of^ simple^ columnar
epithelium^ with^ many^ goblet^ cells.^ Note^ the^ highly
cellular^ loose
CT^ or^ lamina^ propria (LP,^ star)^ directly^ underneath
the^ epithelium^ that^ contains^ abundant^ lymphocytes.
Also note^ the^ intense^ eosinophilic layer^ underlying the^ epithelium^ and^ LP,^ which^ is^ smooth^ muscle
(yellow^ arrow) and^ can^ be^ distinguished^ from^ the^ paler^ staining
DICT^ (black^ line^ spans^ this^ region)^ that^ sits^ directly
below^ the smooth^ muscle^ layer.^ Note^ that^ the^ eosinophilic CT
fibers^ in^ the^ DICT stain^ less^ intensely^ compared
to^ the smooth^ muscle^ layer.^ Can^ you^ explain^ why^ this
is^ the^ case?
Bloomington,^ Male^ reproductive^ tract^ folder,^ epididymis
#5^ ‐^ Example^ of^ pseudostratified columnar^ epithelium
with^ stereocilia.
Here^ there^ are^2 layers^ of^ epithelial^ cells,^ tall^ columnar
cells^ that^ are^ taller^ than^ they^ are^ wide^ with^ prominent
elongated^ nuclei located^ at^ the^ basal^ region^ of^ the^ cells^ (black^ arrow).^ Underlying
the^ columnar^ cells^ are^ simple^ cuboidal^ cells^ (yellow^ arrow)
that contain^ round^ centrally^ located^ nuclei.^ It^ is^ difficult^ to^
appreciate^ here^ that^ both^ of^ these^ types^ of^ epithelial^
cells^ are^ in^ fact^ in^ contact with^ the^ basement^ membrane,^ making^ this^ a^ pseudostratified epithelium.
Also^ note^ the^ prominent^ cell^ surface^ specialization^ of
very long^ stereocilia.^ Terminal^ bars,^ eosinophilic punctate^ structures
(blue^ arrow),^ consisting^ of^ tight^ junctions,^ adherens junctions
and actin^ fibers^ are^ easily^ visualized^ in^ this^ epithelium.^ What
cytoskeletal^ filament^ forms^ the^ core^ of^ stereocilia?
NW^ Olfactory^ epithelium^ #64‐^ Example^ of^ pseudostratified columnar
epithelium^ with^ cilia.^ Here^ it^ appears^ that there^ are^ multiple^ cell^ layers^ in^ this^ epithelium
because^ you^ can^ see^ nuclei^ stacked^ upon^ each
other.^ Believe^ it or^ not,^ this^ is^ a^ psuedostratified epithelium.^ All
of^ these^ cells^ contact^ the^ basement^ membrane,
although^ not all^ of^ them^ reach^ the^ free^ surface.^ Zoom^ in^ and
note^ that^ the^ apical^ surface^ contains^ cilia.^ Other
features^ to note^ in^ this^ tissue^ are^ the^ ducts^ of^ glandular^ epithelium
lined^ by^ simple^ cuboidal^ epithelium^ (black^ arrows), numerous^ blood^ vessels^ lined^ by^ simple^ squamous
epithelium^ (yellow^ arrows),^ and^ nerve^ tissue^
that^ you’ll^ be learning^ about^ soon^ (blue^ arrows).^ It’s^ another
look^ alike^ for^ muscle^ and^ CT.
NW^ Esophagus^ #121^ – Example^ of^ stratified^ squamous,
non‐keratinized^ epithelium^ lining^ the^ esophagus.
Note
the^ multiple^ layers^ of^ nuclei.^ The^ larger^ nuclear
to^ cytoplasmic^ ratio^ in^ the^ basal^ layer^ of^ this^ epithelium
makes this^ region^ of^ the^ epithelium^ appear^ more^ basophilic
(black^ arrow).^ As^ the^ cells^ differentiate^ and^ move
toward the^ free^ surface^ (follow^ the^ blue^ arrow^ towards
its^ tip),^ the^ cells^ initially^ appear^ larger,^ the^ nuclei
more euchromatic,^ and^ they^ produce^ more^ keratin.^
Near^ the^ free^ surface^ the^ cells^ become^ squamous,
and^ their nuclei^ become^ smaller^ and^ flattened.^ Remember
that^ the^ appearance^ of^ the^ surface^ cells^ are^ used
to^ classify this^ epithelium^ as^ stratified^ squamous.^ The^ yellow
arrow^ indicates^ the^ underlying^ loose^ CT,^ which
is^ highly cellular^ and^ has^ small^ CT^ fibers.
NW^ Parotid^ gland^ #135 – Example^ of^ stratified
cuboidal^ to^ columnar^ epithelium.^ The^ ducts^ of
the^ major
salivary^ glands^ are^ one^ of^ the^ few^ places^ you’ll
find^ stratified^ cuboidal^ to^ columnar^ epithelium
(star^ is^ in^ lumen of^ excretory^ duct).^ Zoom^ in^ and^ note^ how^ there
are^2 layers^ of^ epithelium,^ with^ the^ uppermost
being^ cuboidal to^ low^ columnar^ in^ shape.^ Take^ a^ moment^ to^ study
the^ features^ of^ the^ serous^ secreting^ glandular
epithelium^ of the^ parotid^ gland^ (arrows).^ Where^ are^ the^ basal
and^ apical^ regions^ of^ the^ glandular^ epithelium?
Also,^ note^ the DICT^ surrounding^ the^ duct^ and^ blood^ vessels.^
What^ type^ of^ epithelium^ lines^ the^ blood^ vessels
seen^ to^ the^ left of^ the^ duct?
NW^ Thick^ skin^ #72 –Example^ of^ simple^ coiled^ tubular
glandular^ epithelium^ of^ an^ eccrine sweat^ gland
(black
arrows)^ found^ in^ the^ dermis^ of^ the^ skin.^ Three
main^ types^ of^ epithelial^ cells^ make^ up^ the^ glands,
clear^ cells, dark^ cells,^ and^ myoepithelial cells^ organized^ as
pseudostratified epithelium.^ All^ these^ cells^ contact
the basement^ membrane.^ That^ sure^ is^ hard^ to^ see,
though^ isn’t^ it?^ The^ blue^ arrows^ indicate^ ducts
of^ the^ sweat gland,^ which^ are^ an^ example^ of^ stratified^ cuboidal
epithelium.^ There^ are^ two^ layers^ of^ cells^ and^ the
layer^ closest to^ the^ lumen^ is^ cuboidal^ in^ shape,^ about^ as^ tall
as^ they^ are^ wide,^ with^ centrally^ located^ nuclei.
Also^ note^ the DICT^ and^ adipose^ tissue.
