Chapter 2
Epithelium
1.General feature:
1) contain more cells and less extracellular ground
substance
2) Polarisaton:
---free outer surface,face air or other things
---basal surface,face underlying CT,
havebasement membrane
3) Avascularity,but innervation:
---no blood vessels
---rich in nerve terminals
4) Having functions of protection,secretion,
absorption excretion and sensory reception
2.Classification
1) Covering epithelium,the epithelium which cover
body surface or line the inner surface of body
cavities,tubes and sac.
2) Glandular epithelium,the epithelium which main
function is secretion.
3) Sensory epithelium,the epithelium which has
special sensory function.
3.Covering epithelium:
According to the number of layer and shape of
cells
Simple epi.,---simple squamous epi.
---simple cuboidal epi.
---simple columnar epi.
---pseudostratified ciliated columnar epi.
Stratified epi.,---stratified squamous epi.
---stratified columnar epi.
---transitional epi.
1) simple squamous epi:
---structural feature,
/one layer flattened cells,cell border are interdigitate
/with flattened ellipsoid nucleus
---distribution:
mesothelium,the simple squamous epi,which
line the inner surface of body cavities such as
thoracic,pericardiac and abdominal cavities.
endothelium,the simple squamous epi.which
line the inner surface of cardiovascular and
lymphatic system.
other place,alveoli,parietal layers of renal
capsule.
---function,a) transport of materials
b) facilitates movement of viscera
2) simple cuboidal epi.:
---structural feature:
one layer of cells,with same height and width(in
side view) and hexagonal outline in surface view.
spherical centrally-located nucleus
---distribution,/the renal tubule
/thyroid
/the some ducts of mang glands
---main function,covering and secretion
3) simple columnar epi.:
---structural features:
one layer of columnar cells,with basally
lacated ovoid nucleus
goblet cell,scattered,secreting granules-
mucinogen granules-mucus
---distribution,/gastrointestinal tract
/gall bladder
/uterus
---function,secretion and absorption
4) pseudostratified ciliated columnar epi.:
---structural feature,four types of cells
/columnar cell:ciliated
/fusiform cell
/basal cell:pyramid-shaped
/goblet cell
---distribution,inner surface of large duct of respiratory
/trachea
/bronchi
/nasal
5) stratified squamous epi.:
---structural features:
deepest(basal)cells:one layer of cuboidal cells
intermediate regions:several layers of
polygonal –shaped cells
to the surface,more and more flattened
---distributon:
non-karatinised:mouth,pharynx,
oesophagus,urethra and vagina
karatinised,the surface of body,make
up the skin
6) transitional epi.:
---structural feature:
flexible-including the number of layers and shape of
cells
in the distended bladder,there are two to three
layers of cells,The cells become flattened.
in the contracted bladder, there are six to seven
layers of cells.
The surface cells are very large and cuboidal in shape,
covering several deep cells.
---distribution,bladder
4,Epithelial
specializations
1) Specialisations of free
surface
① cell coat:
---defination,a thick layer of
extracellular glycoprotein
---function,adherence,
supporting,protection,
exchange of material and
recognize
② microvilli:
---defination,delicate
finger-liked projections
of cell-membrane and
cytoplasm protruding
from the free surface
---structure:
0.1um in diameter,with different longth.
surface,cell membrane with cell coat
core,longitudinal microfilament-actin filament
fixed on terminal web
terminal web,made up of transverse-arranged
filament at the apical side of cells
---function,increase the surface areas
---distribution,/striated border,intestinal epi.cell
/brush border,proximal renal tubule
③ cilia:
---defination,elongated,mobile projections of
cell membrane and cytoplasm protruding
from free surface
---structure:
5-10um long,300-500nm in diameter
surface,cell membrane
core,microtubules,9X2+2,dynein
basal body,centrioles-connected with microtubules
---function,swing to produce a forward-moving
wave
---distribution,epithelial cells of respiratory tract
2) specializations of the lateral
surface
---intercellular connection of adjacent cells:
non-special,the minute space and
cadherin-cell adherent molecules
special,junctional structures
① Tight junction( zonula
occludens):
---structure:
apical part
point-liked fused between
adjacent cells
arranged in 2-4 thread-liked
structures
form anastomosing network
---function,seal the space
between cells
② intermediate
junction(zonula adherens):
---structure:
below the tight junction
a gap of 15-20nm in width with
medium electron-density filament
material
plaque of electron-dense
materials,with attached
microfilament-make up of
terminal web
---function:
/adherens
/keep the cell shape
/transfer cell contract force
③ desmosome(macula
adherens):
---structure:
plate or spot-shaped
a gap of 20-30 nm,with low
electron-density filaments
interdigitate to form
intermediate line
attachment plaque,with
attached tonofilament(10nm)-
intermediate filament(karatin)
---function,firmly connection
④ gap junction(communicating junction):
---structure:
the smallest gap of 2-3 nm
connexons:
-consist of protein
-7~9nm in diameter
-composed of 6-subunits of proteins- connexin
-2nm channel,hydrophilic channel
---function,provide a pathway between cells
*junctional complex,four
types of junctional
structures(at least two
types) get together.
3) specialization of basal
surface
① basement membrane:
---defination,a sheet of membrane-liked
amorphous material interposed between
epi.cells and underlying CT.
---structure:
HE,pink colour,hard to see
EM,three layers
--lamina lucida,10-50 nm,electron-lucent
--basal lamina,20-300 nm,electron-dense,
thread-liked and amorphous ground
substance,produced by epi,Cell
--reticular lamina,RT+ground substance,
produced by CT
glycoprotein,laminin,type IV collagen,
heparin sulfate proteoglycan and fibronectin
---function:
support,connection,fixaton
semi-premeable membrane
induce the movement,proliferation and
differentiation of epi.cell
② plasma membrane infolding(basal
longitudinal striation):
---defination,the infolding of cell-membrane with
many mitochondria at the basal surface of epi.cell
---function:
increase the basal surface areas
facilitate the passage of water and ions
---distribution,mainly in proximal and distal
renal tubule.
③ hemidesmosomes
---is half of desmosome.
5,Glandular epi,and gland
glandular epi.,epi are specialized for
secretion
gland,organs composed mainly of
glandular epi.
1)classification:
? exocrine gland,discharge the secretion
through a duct system
? endocrine gland,release the secretion
directly into blood steam
2) structure of exocrine gland:
① acinus(secreting unit),according the nature of
secretion
a,serous acinus,serous secretory cells
---structure:
pyramid-shaped cell
basally-located round nucleus
acidophilic cytoplasm-eosinophilic zymogen
granules-contain enzymes
EM,RER,Golgi complex
---function,produce a serous secretion
b,mucous acinus,mucous secreting cells
---structure:
pyramid-shaped cell
flattened dark nucleus against the basal cell
membrane
slightly basophilic cytoplasm-large mucigen
granules
EM,some RER,Golgi complex
---function,secretes mucus
c,mixed acinus,two types of cells
---structure:
mucous acinus
with several serous cells attach on one side-
serous demilune
② ducts:
---from simple squamous epi to simple
columnar or stratified epi.
---carry out the secretions
---secrete or absorb water and ions
Epithelium
1.General feature:
1) contain more cells and less extracellular ground
substance
2) Polarisaton:
---free outer surface,face air or other things
---basal surface,face underlying CT,
havebasement membrane
3) Avascularity,but innervation:
---no blood vessels
---rich in nerve terminals
4) Having functions of protection,secretion,
absorption excretion and sensory reception
2.Classification
1) Covering epithelium,the epithelium which cover
body surface or line the inner surface of body
cavities,tubes and sac.
2) Glandular epithelium,the epithelium which main
function is secretion.
3) Sensory epithelium,the epithelium which has
special sensory function.
3.Covering epithelium:
According to the number of layer and shape of
cells
Simple epi.,---simple squamous epi.
---simple cuboidal epi.
---simple columnar epi.
---pseudostratified ciliated columnar epi.
Stratified epi.,---stratified squamous epi.
---stratified columnar epi.
---transitional epi.
1) simple squamous epi:
---structural feature,
/one layer flattened cells,cell border are interdigitate
/with flattened ellipsoid nucleus
---distribution:
mesothelium,the simple squamous epi,which
line the inner surface of body cavities such as
thoracic,pericardiac and abdominal cavities.
endothelium,the simple squamous epi.which
line the inner surface of cardiovascular and
lymphatic system.
other place,alveoli,parietal layers of renal
capsule.
---function,a) transport of materials
b) facilitates movement of viscera
2) simple cuboidal epi.:
---structural feature:
one layer of cells,with same height and width(in
side view) and hexagonal outline in surface view.
spherical centrally-located nucleus
---distribution,/the renal tubule
/thyroid
/the some ducts of mang glands
---main function,covering and secretion
3) simple columnar epi.:
---structural features:
one layer of columnar cells,with basally
lacated ovoid nucleus
goblet cell,scattered,secreting granules-
mucinogen granules-mucus
---distribution,/gastrointestinal tract
/gall bladder
/uterus
---function,secretion and absorption
4) pseudostratified ciliated columnar epi.:
---structural feature,four types of cells
/columnar cell:ciliated
/fusiform cell
/basal cell:pyramid-shaped
/goblet cell
---distribution,inner surface of large duct of respiratory
/trachea
/bronchi
/nasal
5) stratified squamous epi.:
---structural features:
deepest(basal)cells:one layer of cuboidal cells
intermediate regions:several layers of
polygonal –shaped cells
to the surface,more and more flattened
---distributon:
non-karatinised:mouth,pharynx,
oesophagus,urethra and vagina
karatinised,the surface of body,make
up the skin
6) transitional epi.:
---structural feature:
flexible-including the number of layers and shape of
cells
in the distended bladder,there are two to three
layers of cells,The cells become flattened.
in the contracted bladder, there are six to seven
layers of cells.
The surface cells are very large and cuboidal in shape,
covering several deep cells.
---distribution,bladder
4,Epithelial
specializations
1) Specialisations of free
surface
① cell coat:
---defination,a thick layer of
extracellular glycoprotein
---function,adherence,
supporting,protection,
exchange of material and
recognize
② microvilli:
---defination,delicate
finger-liked projections
of cell-membrane and
cytoplasm protruding
from the free surface
---structure:
0.1um in diameter,with different longth.
surface,cell membrane with cell coat
core,longitudinal microfilament-actin filament
fixed on terminal web
terminal web,made up of transverse-arranged
filament at the apical side of cells
---function,increase the surface areas
---distribution,/striated border,intestinal epi.cell
/brush border,proximal renal tubule
③ cilia:
---defination,elongated,mobile projections of
cell membrane and cytoplasm protruding
from free surface
---structure:
5-10um long,300-500nm in diameter
surface,cell membrane
core,microtubules,9X2+2,dynein
basal body,centrioles-connected with microtubules
---function,swing to produce a forward-moving
wave
---distribution,epithelial cells of respiratory tract
2) specializations of the lateral
surface
---intercellular connection of adjacent cells:
non-special,the minute space and
cadherin-cell adherent molecules
special,junctional structures
① Tight junction( zonula
occludens):
---structure:
apical part
point-liked fused between
adjacent cells
arranged in 2-4 thread-liked
structures
form anastomosing network
---function,seal the space
between cells
② intermediate
junction(zonula adherens):
---structure:
below the tight junction
a gap of 15-20nm in width with
medium electron-density filament
material
plaque of electron-dense
materials,with attached
microfilament-make up of
terminal web
---function:
/adherens
/keep the cell shape
/transfer cell contract force
③ desmosome(macula
adherens):
---structure:
plate or spot-shaped
a gap of 20-30 nm,with low
electron-density filaments
interdigitate to form
intermediate line
attachment plaque,with
attached tonofilament(10nm)-
intermediate filament(karatin)
---function,firmly connection
④ gap junction(communicating junction):
---structure:
the smallest gap of 2-3 nm
connexons:
-consist of protein
-7~9nm in diameter
-composed of 6-subunits of proteins- connexin
-2nm channel,hydrophilic channel
---function,provide a pathway between cells
*junctional complex,four
types of junctional
structures(at least two
types) get together.
3) specialization of basal
surface
① basement membrane:
---defination,a sheet of membrane-liked
amorphous material interposed between
epi.cells and underlying CT.
---structure:
HE,pink colour,hard to see
EM,three layers
--lamina lucida,10-50 nm,electron-lucent
--basal lamina,20-300 nm,electron-dense,
thread-liked and amorphous ground
substance,produced by epi,Cell
--reticular lamina,RT+ground substance,
produced by CT
glycoprotein,laminin,type IV collagen,
heparin sulfate proteoglycan and fibronectin
---function:
support,connection,fixaton
semi-premeable membrane
induce the movement,proliferation and
differentiation of epi.cell
② plasma membrane infolding(basal
longitudinal striation):
---defination,the infolding of cell-membrane with
many mitochondria at the basal surface of epi.cell
---function:
increase the basal surface areas
facilitate the passage of water and ions
---distribution,mainly in proximal and distal
renal tubule.
③ hemidesmosomes
---is half of desmosome.
5,Glandular epi,and gland
glandular epi.,epi are specialized for
secretion
gland,organs composed mainly of
glandular epi.
1)classification:
? exocrine gland,discharge the secretion
through a duct system
? endocrine gland,release the secretion
directly into blood steam
2) structure of exocrine gland:
① acinus(secreting unit),according the nature of
secretion
a,serous acinus,serous secretory cells
---structure:
pyramid-shaped cell
basally-located round nucleus
acidophilic cytoplasm-eosinophilic zymogen
granules-contain enzymes
EM,RER,Golgi complex
---function,produce a serous secretion
b,mucous acinus,mucous secreting cells
---structure:
pyramid-shaped cell
flattened dark nucleus against the basal cell
membrane
slightly basophilic cytoplasm-large mucigen
granules
EM,some RER,Golgi complex
---function,secretes mucus
c,mixed acinus,two types of cells
---structure:
mucous acinus
with several serous cells attach on one side-
serous demilune
② ducts:
---from simple squamous epi to simple
columnar or stratified epi.
---carry out the secretions
---secrete or absorb water and ions
