chapter 2 epithelium
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Chapter 2 Epithelium. 1.General feature: 1) contain more cells and less extracellular ground substance 2) Polarisaton : --- free surface: face air or other things --- basal surface: have basement membrane, to face underlying connective tissue (CT) - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 2Chapter 2
Epithelium Epithelium
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1.General feature:1) contain more cells and less extracellular ground s
ubstance2) Polarisaton: ---free surface: face air or other things ---basal surface: have basement membrane, to face underlying connective tissue (CT) 3) Avascularity, but innervation: ---no blood vessels ---rich in nerve terminals4) Having functions of protection, secretion, absorptionand sensory reception
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2.Classification of Epithelium
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.
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3. Classification of covering epithelium: According to the number of layer and shape
of cellsSimple epi.: ---simple squamous epi. ---simple cuboidal epi. ---simple columnar epi. ---pseudostratified ciliated column
ar epi.
Stratified epi.: ---stratified squamous epi. ---stratified columnar epi. ---transitional epi.
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1)1) simple squamous epi:simple squamous epi:
---structural feature:
one layer flattened cells, cell border are interdigitate
with flattened ellipsoid nucleus
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---distribution: • mesothelium: the simple squamous epi. w
hich 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
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Vascular endothelium
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Mesothelium on Mesothelium on abdominal cavityabdominal cavity
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2) simple cuboidal epi.:
---structural feature: • one layer of cells, with same height and width , hex
agonal outline in surface view.• spherical centrally-located nucleus
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---distribution: /the renal tubule
/thyroid
/the some ducts of glands
---function: covering and secretion
thyroidrenal tubule
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3) simple columnar epi.:
---structural features: • one layer of columnar cells, with basally locate
d ovoid nucleus•
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---distribution: gastrointestinal tract gall bladder uterus---function: secretion and absorption
goblet cell: scattered, secreting granules-mucinogen granules-mucus
goblet cellsimple columnar epi
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4) pseudostratified ciliated columnar epi.:
---Structural feature: 1, Four types of cellscolumnar cell (ciliated); goblet cellfusiform cell; basal cell: pyramid-shaped
2, Every cell locate on basement membrance: Simple epi.
four types of cells
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---distribution: inner surface of large duct of respiratory
trachea
bronchi
nasal
The epithelium of trachea
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5) stratified squamous epi.:
---structural features: • deepest (basal) cells: one layer of cuboidal cells• the cells in intermediate regions: several layers
of polygonal –shaped cells • to the surface: more and more flattened cells
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---distributon: • non-karatinised: mouth, pharynx, oesophag
us, urethra and vagina
• karatinised: the surface of body, make up the skin
non-karatinised karatinised
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6) transitional epi.:
• 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.
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---distribution: bladder---distribution: bladder
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in the in the contracted bladderbladder
in the distendeddistended bladder
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4. Epithelial specializations4. Epithelial specializations
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1)1) Specialisations of free surfacSpecialisations of free surfacee
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① microvilli: ---defination: delicate finger-liked projec
tions of cell-membrane and cytoplasm protruding from the free surface
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---structure: • 0.1um in diameter, with different longth.• surface: cell membrane with cell coat• core: longitudinal microfilament-actin filament fix
ed on terminal web• terminal web: made up of transverse-arranged fila
ment at the apical side of cells
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---function: increase the surface areas
---distribution: striated border: intestinal epi. cell
brush border, e.g. proximal renal tubule
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② cell coat: ---defination: a thick layer of extracellular glycoprotein
---function: adherence, supporting, protection, exchange of material and recognize
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③ cilia:---defination: elongated, mobile projections of c
ell membrane and cytoplasm protruding from free surface
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---structure: • 5-10um long, 300-500nm in diameter• surface: cell membrane• core: microtubules, 9X2+2• basal body: centrioles-connected with microtubules
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---function: swing to produce a forward-moving wave
---distribution: epithelial cells of respiratory tract
respiratory tract
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2)2) specializations specializations of the lateral surfaceof the lateral surface
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---intercellular connection of adjacent cells: • non-special: the minute space and cadheri
n -- cell adherent molecules
• special: junctional structures
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① Tight junction (zonula occludens):
---structure: • apical part• point-liked fused between a
djacent cells• arranged in 2-4 thread-liked
structures• form anastomosing network
---function: seal the space between cells
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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
terminal web
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intermediate junction
Tight junction
desmosome
cilia
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③ desmosome (macula adherens):
---structure: • plate or spot-shaped• a gap of 20-30 nm, with low
electron-density filaments interdigitate
• attachment plaque: with attached tonofilament-inter
mediate filament (karatin)
---function: firmly connection
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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
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connexons
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junctional complex: four types of junctional structures (at least two types) get together.
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3)3) specialization of basal surfacespecialization of basal surface
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① basement membrane:---defination: a sheet of membrane-liked amorph
ous material interposed between epi. cells and underlying CT.
---structure: • HE: pink colour, hard to see
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• Under EM: --basal lamina: 20-300 nm, electron-dense, t
hread-liked and amorphous ground substance, produced by epi. cell
--reticular lamina: reticular tissue + ground substance, produced by CT
•
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---function: • support, connection, fixation• semi-premeable membrane• induce the movement, proliferation and differenti
ation of epi. cell
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② plasma membrane infolding
(basal longitudinal striation): ---defination: the infolding of cell-membrane with man
y mitochondria at the basal surface of epi. cell
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---function: • increase the basal surface areas• facilitate the passage of water and ions
---distribution: mainly in proximal renal tubule and distal renal tubule.
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③ hemidesmosomes
---is half of desmosome.
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5. Glandular epi. and gland• glandular epi.: epi are specialized for secreti
on• gland: organs composed mainly of glandula
r epi.
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1)classification: exocrine gland: discharge the secretion through a duct systemendocrine gland: release the secretion directly into blood steam
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2) structure of exocrine gland:
①acinus (secreting unit):
according the nature
of secretion
a. serous acinus:
serous secretory cells
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---structure: • pyramid-shaped cell• basally-located round nucleus• acidophilic cytoplasm: eosinophilic zymogen
granules: contain enzymes• EM: RER, Golgi complex ---function: produce a serous secretion
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b. mucous acinus: mucous secreting cells
---structure: • pyramid-shaped cell• flattened dark nucleus against the basal cell
membrane• slightly basophilic cytoplasm-large mucigen g
ranules• EM: some RER, Golgi complex
---function: secretes mucus
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c. mixed acinus: two types of cells ---structure: • mucous acinus• with several serous cells attach on one side- serous demilune
serous demilune
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② ducts:
---from simple squamous epi to simple columnar or stratified epi.
---carry out the secretions
---secrete or absorb water and ions
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Multichosen question Multichosen question
• 1.The lining epithelium of the serous body cavities (pericardial, pleural and peritoneal) is
• endothelium
• mesothelium
• simple cuboidal epithelium
• stratified squamous epithelium
• transitional epithelium
√
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2. An endocrine gland passes its secretion directly into the
• blood or lymph
• duct
• body surface
• digestive tract
• lumen of acinus
√
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3. The nucleus is flattened against the basal plasma memberane of the cells, the cytoplasm is filled with large mucigen droplets, it is the
• serous cell
• mucous cell
• serous demilune
• goblet cell
• myoepithelial cell
√
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Fill in the blanks Fill in the blanks
In H.E. stain sections, the cytoplasm is stained pink by ___________, the nucleus is stained purple-blue by___________________________.
Hematoxylin
Eosin
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The procedure of preparation of histologic slides includes mainly______________________, ___________,_________________,
_____________, ______________,and sectioning.
Obtaining the specimen
Fixation DehydrationClearing Embedding
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The 4 basic types of tissue are ______________,_________________,_________________ and _________________.
epithelium connective tissuemuscular tissuenervous tissue
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Epithelia are mainly classified into 2 groups: ______________and_______________.
Simple epi. Stratified epi
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The intercellular junctions of epithelial cells are (1) _______________,
(2) ___________________,
(3) _____________, and (4)______________. When 2 or more kinds of them are present together, we called it __________________.
Tight junction
Intermediate junction
DesmosomeGap junction
Junctional complex
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7. Specialized structures on basal surface of epithelial cells are ________________________________,_____________________________ and ______________________.
basement membraneplasma membrane infolding
hemidesmosomes
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8. Pseudostratified columnar ciliated epithelium consists of 4 kinds of cells with different shape and height, but all set on the basal membrane: ________________________,
________________,_____________and ________________.
columnar cell (ciliated)
goblet cell fusiform cellbasal cell
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Questions Questions
• Describe the characteristics of epithelial tissue.
• Describe the structural characteristics and functions of each covering epithelial type.
• Compare the structure of microvilli with cilia.
• Compare the structure of intermediate junction with desmosome.