Chapter 2Chapter 2

Epithelial tissueEpithelial tissue

1.General feature:1.General feature:1) contain more cells and less extracellular ground substance1) contain more cells and less extracellular ground substance2) Polarisaton2) Polarisaton:: ---free outer surface: face the surface of the body or the ---free outer surface: face the surface of the body or the

lumen of an organ or glandlumen of an organ or gland ---basal surface: face underlying connective tissue---basal surface: face underlying connective tissue3)  Avascularity, but innervation3)  Avascularity, but innervation: : ---no blood vessels---no blood vessels ---rich in nerve terminals---rich in nerve terminals4)4) Cellular Layer + Basement Membrane Cellular Layer + Basement Membrane55) Functions: ) Functions: protectionprotection secretionsecretion absorptionabsorption sensory receptionsensory reception

2.Classification of Epithelium2.Classification of Epithelium

1)1)    Covering epithelium:Covering epithelium: the epithelium which cover body the epithelium which cover body surface or line the inner surface of body cavities, tubes surface or line the inner surface of body cavities, tubes and sac.and sac.

2)2)    Glandular epithelium:Glandular epithelium: the epithelium which main the epithelium which main function is secretion.function is secretion.

3)3)    Sensory epithelium:Sensory epithelium: the epithelium which has special the epithelium which has special sensory function.sensory function.

* * Myoepithelial cellMyoepithelial cell

3. Classification of covering epithelium3. Classification of covering epithelium: :

According to the number of layer and shape of According to the number of layer and shape of cellscells

Simple epi.:Simple epi.: --- ---simple squamous epi.simple squamous epi.

---simple cuboidal epi.---simple cuboidal epi.

---simple columnar epi.---simple columnar epi.

---pseudostratified ciliated columnar epi.---pseudostratified ciliated columnar epi.

Stratified epi.:Stratified epi.: ---stratified squamous epi.---stratified squamous epi.

---stratified columnar epi.---stratified columnar epi.

---transitional epi.---transitional epi.

Cell shapeCell shape

Cell Layers

Simple

Stratified

1)1)            simple squamous epi:simple squamous epi:

---structural feature:---structural feature:

/one layer flattened cells, cell border are interdigitate closely/one layer flattened cells, cell border are interdigitate closely

/with flattened ellipsoid nucleus/with flattened ellipsoid nucleus

---Distribution: ---Distribution: • mesothelium:mesothelium: the simple squamous epi. which the simple squamous epi. which

line the inner surface of body cavities such as line the inner surface of body cavities such as thoracic, abdominal cavities and pericardiac thoracic, abdominal cavities and pericardiac ..

• endothelium:endothelium: the simple squamous epi. which the simple squamous epi. which line the inner surface of cardiovascular and line the inner surface of cardiovascular and lymph vessels.lymph vessels.

• other placeother place:: alveoli, parietal layers of renal alveoli, parietal layers of renal capsule.capsule.

---function:---function: a) transport of materials a) transport of materials b) facilitates movement of viscerab) facilitates movement of viscera

Vascular Vascular endotheliumendothelium

Mesothelium on Mesothelium on abdominal cavityabdominal cavity

2)2)            simple cuboidal epi.:simple cuboidal epi.:

---structural feature:---structural feature: • one layer of cells, with same height and width , hexagonal one layer of cells, with same height and width , hexagonal

in shape.in shape.• spherical centrally-located nucleusspherical centrally-located nucleus

---distribution:---distribution: /the renal tubule /the renal tubule

/thyroid/thyroid

/the some ducts of glands/the some ducts of glands

---function:---function: covering and secretion covering and secretion

thyroidrenal tubule

3)3)            simple columnar epi.:simple columnar epi.:

----structural features:--structural features: • one layer of columnar cells, with basally located one layer of columnar cells, with basally located

ovoid nucleusovoid nucleus

---distribution:---distribution: gastrointestinal tract gastrointestinal tract gall bladdergall bladder uterusuterus---function:---function: secretion and absorption secretion and absorption

goblet cell: scattered, secreting granules-mucusgoblet cell: scattered, secreting granules-mucus

goblet cellsimple columnar epi

4)4)            pseudostratified ciliated columnar epi.:pseudostratified ciliated columnar epi.:

---Structural feature:---Structural feature: 1, Four types of cells1, Four types of cellscolumnar cell (ciliated); goblet cellcolumnar cell (ciliated); goblet cellfusiform cell; basal cell: pyramid-shapedfusiform cell; basal cell: pyramid-shaped

2, Every cell locate on basement membrane: 2, Every cell locate on basement membrane: Simple epi.Simple epi.

four types of cells

---distribution:---distribution:

inner surface of large inner surface of large duct of respiratory passagesduct of respiratory passages

tracheatrachea

bronchibronchi

nasalnasal

The epithelium of trachea

5)5)            stratified squamous epi.:stratified squamous epi.:

---structural features:---structural features: • deepest (basal) cells: deepest (basal) cells: one layer of cuboidal cellsone layer of cuboidal cells• the cells in intermediate regions: the cells in intermediate regions: several layers of several layers of

polygonal –shaped cells polygonal –shaped cells • to the surface: to the surface: more and more flattened cellsmore and more flattened cells

---distributon:---distributon:

• non-keratinised:non-keratinised: mouth, pharynx, oesophagus, mouth, pharynx, oesophagus, urethra and vaginaurethra and vagina

• keratinised:keratinised: the surface of body, make up the the surface of body, make up the skinskin

non-karatinised karatinised

6)6)    transitional epithelium:transitional epithelium:

• Flexible qualitiesFlexible qualities

---ncluding the number of layers and shape ---ncluding the number of layers and shape of cellsof cells

---distribution: bladder---distribution: bladder

in the in the contracted bladderbladder

in the distendeddistended bladder

4. 4. Epithelial Epithelial specializations specializations

Sides of cells:--- Apical (free)--- Basal--- Lateral

1)1)            Specializations of free surfaceSpecializations of free surface

①①        microvilli:microvilli: ---definition:---definition: delicate finger-liked projections of cell- delicate finger-liked projections of cell-

membrane and cytoplasm protruding from the free surfacemembrane and cytoplasm protruding from the free surface

---structure:---structure: • 0.1um in diameter, with different longth.0.1um in diameter, with different longth.• surface: cell membrane with cell coatsurface: cell membrane with cell coat• core: longitudinal microfilament-actin filament core: longitudinal microfilament-actin filament

fixed on terminal webfixed on terminal web• terminal web: made up of transverse-arranged terminal web: made up of transverse-arranged

filament at the apical side of cellsfilament at the apical side of cells

---function:---function: increase the surface areas, thus aid in the increase the surface areas, thus aid in the processes of secretion and absorption.processes of secretion and absorption.

---distribution:---distribution: /striated border: intestinal epi. cell /striated border: intestinal epi. cell

/brush border: proximal renal tubule/brush border: proximal renal tubule

Striated borderStriated border

②② cell coat:cell coat:

---definition:---definition: a thick layer of extracellular glycoproteina thick layer of extracellular glycoprotein

---function:---function: adherence, supporting, protection, exchange of material and recognizeadherence, supporting, protection, exchange of material and recognize

     ③     ③ cilia:cilia:---definition:---definition: elongated, mobile projections of cell elongated, mobile projections of cell

membrane and cytoplasm protruding from free membrane and cytoplasm protruding from free surfacesurface

---structure:---structure:

• 5-10um long, 300-500nm in diameter5-10um long, 300-500nm in diameter

• surface: cell membranesurface: cell membrane

• core: microtubules, 9X2+2core: microtubules, 9X2+2

• basal body: basal body:

centrioles-connected with microtubules of ciliacentrioles-connected with microtubules of cilia

---function:---function: beat in a rhythmical manner and produce a beat in a rhythmical manner and produce a forward-moving wave forward-moving wave

---distribution:---distribution: epithelial cells of respiratory tract epithelial cells of respiratory tract

respiratory tract

2)2)    specializations specializations of the lateral surface of the lateral surface

---intercellular connection of adjacent cells: ---intercellular connection of adjacent cells:

• non-special manner: the minute space and adherent non-special manner: the minute space and adherent molecules (glycoproteins, proteoglycans, cadherin)molecules (glycoproteins, proteoglycans, cadherin)

• Special manner: junctional structuresSpecial manner: junctional structures

①①  Tight junction (zonula occludens):Tight junction (zonula occludens):

---structure:---structure: • apical partapical part

• point-liked fused between adjacent point-liked fused between adjacent cellscells• arranged in 2-4 thread-likedarranged in 2-4 thread-liked structuresstructures• form anastomosing networkform anastomosing network

---function:---function: seal the space between cellsseal the space between cells

 ② ② intermediate junction (zonula intermediate junction (zonula adherens):adherens):

---structure: ---structure:

• below the tight junctionbelow the tight junction• a gap of 15-20nm in width with a gap of 15-20nm in width with

medium electron-density filament medium electron-density filament materialmaterial

• plaque plaque of electron-dense materials, of electron-dense materials, with attached microfilament-make up with attached microfilament-make up of of terminal webterminal web

---function:---function: /adherens/adherens /keep the cell shape/keep the cell shape /transfer cell contract force/transfer cell contract force

③③ desmosome (macula adherens):desmosome (macula adherens):

---structure:---structure:

• plate or spot-shapedplate or spot-shaped

• a gap of 20-30 nm, witha gap of 20-30 nm, with

low electron-density filaments low electron-density filaments

interdigitateinterdigitate

• attachment plaqueattachment plaque

• Many tonofilaments are inserted into Many tonofilaments are inserted into attachment plaque, each filament attachment plaque, each filament make a hairpin loop and then passes make a hairpin loop and then passes back into the cytoplasmback into the cytoplasm

• ---function:---function:

firmly connectionfirmly connection

④④ gap junction gap junction (communicating (communicating junction):junction):

---structure:---structure: • the smallest gap of 2-3 nmthe smallest gap of 2-3 nm• connexonsconnexons:: -consist of protein-consist of protein -7~9nm in diameter-7~9nm in diameter -composed of 6-subunits of -composed of 6-subunits of

proteinsproteins- connexin- connexin -2nm channel: electron-lucid -2nm channel: electron-lucid

central channelcentral channel---function:---function: provide a ions and small molecules provide a ions and small molecules

pathway between cellspathway between cells

connexons

junctional complex:junctional complex:

at least two types of junctional structures get at least two types of junctional structures get together.together.

3)3)            specialization of basal surfacespecialization of basal surface

①①    basement membrane:basement membrane:---definition:---definition: a sheet of membrane-liked amorphous a sheet of membrane-liked amorphous

material interposed between epithelium cells and material interposed between epithelium cells and underlying CT.underlying CT.

---structure:---structure:

• HE: pink colour, hard to seeHE: pink colour, hard to see

• PAS +PAS +

• EM: two layersEM: two layers ----basal laminabasal lamina: 20-300 nm, electron-dense, : 20-300 nm, electron-dense,

thread-liked and amorphous ground substance, thread-liked and amorphous ground substance, produced by epithelium Cellproduced by epithelium Cell

----reticular laminareticular lamina: RT+ground substance, : RT+ground substance, produced by CTproduced by CT

---function:---function:

• support, connection, fixationsupport, connection, fixation

• semi-permeable membranesemi-permeable membrane

• induce the movement, proliferation and induce the movement, proliferation and differentiation of epithelium celldifferentiation of epithelium cell

 ② ② plasma membrane infoldingplasma membrane infolding

(basal longitudinal striation):(basal longitudinal striation): ---definition:---definition: the infolding of cell-membrane with many the infolding of cell-membrane with many

mitochondria at the basal surface of epithelium cellmitochondria at the basal surface of epithelium cell

---function:---function:

• increase the basal surface areasincrease the basal surface areas

• facilitate the passage of water and ionsfacilitate the passage of water and ions

---distribution:---distribution: mainly in proximal and distal renal mainly in proximal and distal renal tubule.tubule.

③③    hemidesmosomeshemidesmosomes

---is half of desmosome.---is half of desmosome.

SUMMARY 1SUMMARY 1 ：：上皮类型 主要分布

单层上皮 单层扁平上皮 内皮：循环管道内表面间皮：胸膜、腹膜、心包膜、其它：肺泡、肾小囊等

单层立方上皮 肾小管、甲状腺滤泡等单层柱状上皮 胃肠、胆囊、子宫内膜等假复层纤毛柱状上皮 呼吸管道

复层上皮 复层扁平上皮 角化型：皮肤表皮非角化型：口腔、食管、阴道

复层柱状上皮 睑睫膜、男性尿道等变移上皮 肾盏、肾盂、输尿管、膀胱

SUMMARY 2SUMMARY 2 ：：名 称 结 构 特 点 主 要 功 能

游离面微绒毛 细指状，光镜不可见，有微丝 吸收

纤毛 粗指状，光镜下可见，有微管 定向摆动

侧 面

紧密连接 点状融合 机械连接

中间连接 小盘状融合 机械连接

桥粒 斑状融合 机械连接

缝隙连接 点状，成群，细胞间有通道 细胞通讯

基底面

基膜 薄膜，分基板和网板， PAS 阳性，嗜银

连接、支持、半透膜

质膜内褶 膜向胞内折叠，线粒体多 吸收

半桥粒 桥粒的一半 固定

5. Glandular epithelium and gland 5. Glandular epithelium and gland (study yourself )(study yourself )

• glandular epithelium: are specialized for secretionglandular epithelium: are specialized for secretion• gland: organs composed mainly of glandular gland: organs composed mainly of glandular

epiitheliumepiithelium

1) Classification:1) Classification: exocrine gland: exocrine gland: discharge the secretion through a duct systemdischarge the secretion through a duct systemendocrine gland: endocrine gland: release the secretion directly into blood steamrelease the secretion directly into blood steam

2) structure of exocrine gland: 2) structure of exocrine gland:

Simple gland compound alveolar gland compound tubulo-alveolar glandSimple gland compound alveolar gland compound tubulo-alveolar gland

① acinus (secreting unit): according the nature of secretion

a. serous acinus: serous secretory cells

---structure:---structure: • pyramid-shaped cellpyramid-shaped cell• basally-located round nucleusbasally-located round nucleus• acidophilic cytoplasm-eosinophilic zymogen acidophilic cytoplasm-eosinophilic zymogen

granules-contain enzymesgranules-contain enzymes• EM: RER, Golgi complexEM: RER, Golgi complex---function:---function: produce a serous secretion produce a serous secretion

b. Mucous acinus:b. Mucous acinus: mucous secreting cells mucous secreting cells

---structure:---structure:

• pyramid-shaped cellpyramid-shaped cell

• flattened dark nucleus against the basal cell flattened dark nucleus against the basal cell membranemembrane

• slightly basophilic cytoplasm-large mucigen slightly basophilic cytoplasm-large mucigen granulesgranules

• EM: some RER, Golgi complexEM: some RER, Golgi complex

---function:---function: secretes mucus secretes mucus

Mucous acinusMucous acinus

c.c.    mixed acinus:mixed acinus: two types of cells two types of cells ---structure:---structure: • mucous acinusmucous acinus• with several serous cells attach on one side- serous demilunewith several serous cells attach on one side- serous demilune

②②    ducts: ducts:

---from simple squamous epithelium to simple ---from simple squamous epithelium to simple columnar or stratified epitheliumcolumnar or stratified epithelium

---carry out the secretions---carry out the secretions

---secrete or absorb water and ions---secrete or absorb water and ions

Thank you !Thank you !