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)

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Chapter 2 Epithelium

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Chapter 2 epithelium

Chapter 2Epithelium


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)

3)  Avascularity, but innervation:

---no blood vessels

---rich in nerve terminals

4) Having functions of

protection, secretion,

absorption

and sensory reception


Chapter 2 epithelium

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.


Chapter 2 epithelium

3. Classification of 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

1)simple squamous epi:

---structural feature:

one layer flattened cells, cell border are interdigitate

with flattened ellipsoid nucleus


Chapter 2 epithelium

---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


Vascular endothelium

Vascular endothelium


Mesothelium on abdominal cavity

Mesothelium on abdominal cavity


Chapter 2 epithelium

2)simple cuboidal epi.:

---structural feature:

  • one layer of cells, with same height and width , hexagonal outline in surface view.

  • spherical centrally-located nucleus


Chapter 2 epithelium

---distribution: /the renal tubule

/thyroid

/the some ducts of glands

---function: covering and secretion

renal tubule

thyroid


Chapter 2 epithelium

3)simple columnar epi.:

---structural features:

  • one layer of columnar cells, with basally located ovoid nucleus


Chapter 2 epithelium

---distribution: gastrointestinal tract

gall bladder

uterus

---function: secretion and absorption

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

goblet cell

simple columnar epi


Chapter 2 epithelium

four types of cells

4)pseudostratified ciliated columnar epi.:

---Structural feature:

1, Four types of cells

columnar cell (ciliated); goblet cell

fusiform cell; basal cell: pyramid-shaped

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


Chapter 2 epithelium

---distribution: inner surface of large duct of respiratory

trachea

bronchi

nasal

The epithelium of trachea


Chapter 2 epithelium

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


Chapter 2 epithelium

---distributon:

  • non-karatinised: mouth, pharynx, oesophagus, urethra and vagina

  • karatinised: the surface of body, make up the skin

karatinised

non-karatinised


Chapter 2 epithelium

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.


Distribution bladder

---distribution: bladder


In the contracted bladder

in the contractedbladder

in the distendedbladder


4 epithelial specializations

4. Epithelial specializations


1 specialisations of free surface

1)Specialisations of free surface


Chapter 2 epithelium

①microvilli:

---defination: delicate finger-liked projections of cell-membrane and cytoplasm protruding from the free surface


Chapter 2 epithelium

---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


Chapter 2 epithelium

---function: increase the surface areas

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

brush border, e.g. proximal renal tubule


Chapter 2 epithelium

②cell coat:

---defination: a thick layer of extracellular glycoprotein

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


Chapter 2 epithelium

③     cilia:

---defination: elongated, mobile projections of cell membrane and cytoplasm protruding from free surface


Chapter 2 epithelium

---structure:

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

  • surface: cell membrane

  • core: microtubules, 9X2+2

  • basal body: centrioles-connected with microtubules


Chapter 2 epithelium

---function: swing to produce a forward-moving wave

---distribution: epithelial cells of respiratory tract

respiratory tract


2 specializations of the lateral surface

2)specializations of the lateral surface


Chapter 2 epithelium

---intercellular connection of adjacent cells:

  • non-special: the minute space and cadherin -- cell adherent molecules

  • special: junctional structures


Chapter 2 epithelium

①Tight 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


Chapter 2 epithelium

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


Chapter 2 epithelium

cilia

Tight junction

desmosome

intermediate junction


Chapter 2 epithelium

③desmosome (macula adherens):

---structure:

  • plate or spot-shaped

  • a gap of 20-30 nm, with low electron-density filaments interdigitate

  • attachment plaque:

    with attached tonofilament-intermediate filament (karatin)

    ---function: firmly connection


Chapter 2 epithelium

④gap 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


Chapter 2 epithelium

connexons


Chapter 2 epithelium

junctional complex: four types of junctional structures (at least two types) get together.


3 specialization of basal surface

3)specialization of basal surface


Chapter 2 epithelium

①basement membrane:

---defination: a sheet of membrane-liked amorphous material interposed between epi. cells and underlying CT.

---structure:

  • HE: pink colour, hard to see


Chapter 2 epithelium

  • Under EM:

    --basal lamina: 20-300 nm, electron-dense, thread-liked and amorphous ground substance, produced by epi. cell

    --reticular lamina: reticular tissue + ground substance, produced by CT


Chapter 2 epithelium

---function:

  • support, connection, fixation

  • semi-premeable membrane

  • induce the movement, proliferation and differentiation of epi. cell


Chapter 2 epithelium

② plasma membrane infolding

(basal longitudinal striation):

---defination: the infolding of cell-membrane with many mitochondria at the basal surface of epi. cell


Chapter 2 epithelium

---function:

  • increase the basal surface areas

  • facilitate the passage of water and ions

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


Chapter 2 epithelium

③hemidesmosomes

---is half of desmosome.


Chapter 2 epithelium

5. Glandular epi. and gland

  • glandular epi.: epi are specialized for secretion

  • gland: organs composed mainly of glandular epi.


Chapter 2 epithelium

1)classification:

exocrine gland: discharge the secretion through a duct system

endocrine gland: release the secretion directly into blood steam


Chapter 2 epithelium

2) structure of exocrine gland:

①acinus (secreting unit):

according the nature

of secretion

a.serous acinus:

serous secretory cells


Chapter 2 epithelium

---structure:

  • pyramid-shaped cell

  • basally-located round nucleus

  • acidophilic cytoplasm: eosinophilic zymogen granules: contain enzymes

  • EM: RER, Golgi complex

    ---function: produce a serous secretion


Chapter 2 epithelium

b.mucous acinus: mucous secreting cells

---structure:

  • pyramid-shaped cell

  • flattened dark nucleus against the basal cell membrane

  • slightly basophiliccytoplasm-large mucigen granules

  • EM: some RER, Golgi complex

    ---function: secretes mucus


Chapter 2 epithelium

c.mixed acinus: two types of cells

---structure:

  • mucous acinus

  • with several serous cells attach on one side- serous demilune

serous demilune


Chapter 2 epithelium

②ducts:

---from simple squamous epi to simple columnar or stratified epi.

---carry out the secretions

---secrete or absorb water and ions


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


Chapter 2 epithelium

2. An endocrine gland passes its secretion directly into the

  • blood or lymph

  • duct

  • body surface

  • digestive tract

  • lumen of acinus


Chapter 2 epithelium

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


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


Chapter 2 epithelium

The procedure of preparation of histologic slides includes mainly______________________, ___________,_________________,

_____________, ______________,and sectioning.

Obtaining the specimen

Fixation

Dehydration

Clearing

Embedding


Chapter 2 epithelium

The 4 basic types of tissue are ______________,_________________,_________________ and _________________.

epithelium

connective tissue

muscular tissue

nervous tissue


Chapter 2 epithelium

Epithelia are mainly classified into 2 groups: ______________and_______________.

Simple epi.

Stratified epi


Chapter 2 epithelium

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

Desmosome

Gap junction

Junctional complex


Chapter 2 epithelium

7. Specialized structures on basal surface of epithelial cells are ________________________________,_____________________________ and ______________________.

basement membrane

plasma membrane infolding

hemidesmosomes


Chapter 2 epithelium

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 cell

basal cell


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.


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