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Epithelium I
(the first of four tissues)
Dr. Kelly Selman
November 30, 2007
Reading Assignment:Junqueira & Carneiro, Chapt. 2&4
Gartner & Hiatt, Chapter 2
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Tissues
Consist of cells and extra-cellular (non-cellular) components
that are organized to perform specific functions
Have certain morphological and functional characteristics
Four basic types of tissues:
Epithelium(lines surfaces; glandular secretions)
Connective tissue(support & protection)
Muscle(movement)
Nerve(conducts impulses)
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Paraffin section of the mucosa that linesthe underside of the tongue (H&E)
Epithelium
Connectivetissue
Muscle
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Nerve
Muscle
Connective TissueBlood vessel
Plastic section through the tongueshowing all 4 types of tissue
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EpitheliumWhere found?
Form sheets of cells that cover all internaland external surfaces. Forms barriers.
All glands are made up of epithelium, both
the secretory portions and non secretoryportions (ducts).
Embryological derivation: all 3 germ layers.
Functions:Protection Absorption TransportSecretion Gas Exchange Sensory
**STRUCTURE REFLECTS FUNCTION**
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Morphological characteristics of anepithelium
Cells in close apposition (forms sheets of cells)
Cells rest on a basement membrane(BM)
Cells are adhesive
Intercellular junctions Tissue is avascular
Overlies vascular connective tissue (lamina propria)
(BM)
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Epithelia form polarized sheets of cells
These sheets of cells have a free surface and a surfacethat rests on a basement membrane (BM)
Free surface = apical surface Surface on BM = basal surface
Each cell of an epithelium also has an apical surface
and a basolateral surface with different functions.Regions maintained, in part, by intercellular junctions
Surface modifications of cells reflect functions atthose surfaces
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Organelles are polarized within cells
Junqueira & Carneiro Fig. 4-26
Pancreatic
acinar cell
Exocytosis
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Classification of EpitheliaBased on morphology of cells and NOT on
functional characteristics
Shape ofapical cells
SquamousCuboidal
Columnar
Arrangement ofcells
Simple
Stratified
Pseudostratified
Transitional
Apical surface specializations
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Simple Pseudostratified
Stratified Transitional
Classification of Epithelium
See: Junqueira & Carneiro (Fig. 4-12)
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Simple squamous epithelium
Junqueira & Carneiro
Endothelium:a simple squamousepithelium
4-13 4-14
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Duct
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Striatedborderat apicalsurface
Basement
membrane
A simple
columnarepithelium
may have
more than
1 type cell
within in.
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Basal surfaceNOTE: All cells rest on
basement membrane but
they do not all reach the
free surface Trachea
cilia Free surface
BM
Pseudostratified columnar epitheliumwith cilia (on apical surface)
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Stratified cuboidal epithelium(Note: most apical cells are cuboidal in shape)
Duct of mucous gland
See Junqueira and Carneiro, Fig. 4-33
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Stratified squamous non-keratinizedepithelium
Nuclei at free surface
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Stratified squamous non-keratinized
epithelium (SSE) of oral mucosa
Oral mucosa of cheeks
SSEFree surface( faces oral cavity)
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Stratified squamouskeratinized epithelium
Keratinized layer
Epithelium
Thin skin (H&E) Thick skin (H&E)
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Transitional Epithelium
Urinary bladder, H&E
Basement membrane
Characterized by several layers of nuclei, apical cells
that bulge into the lumen and some cells with 2 nuclei
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Basement membrane
Basement membrane
SEM basement membrane
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Basement membrane (PAS+)
Basement membraneat basal surface (PAS+)
Apicalsurface
Intestinallumen
Intestinal
lumen
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Basement membrane--Thin sheet of extracellular material
at the basal surface of all epithelia
--Separates epithelia from the underlying CT
--Structural attachment site for its overlying epithelial cells and itsunderlying CT
--Synthesized primarily by overlying epithelial cells (+/- CTcells); it is part of extracellular matrix
--Not visible in LM with H&E staining but is PAS+
--Basement membrane is LM term
--Not just found associated with epithelia; External lamina in other
tissue (i.e., muscle cells,adipocytes and Schwann cells)
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In the TEM Basement membrane may consist of 2regions (basal lamina & reticular lamina)
Basal lamina (or
Lamina densa)
Basement membrane in LM (PAS+)
BM has basal lamina and reticular lamina
Basal cytoplasmof epithelial cell
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Basal lamina: always present, synthesized by
epithelial cells, visible only by TEM Lamina lucida (Lamina rara):
translucent & closest to cell membrane
contains fine strands that connect cell tolamina densa
Lamina densa:
electron dense layer (20-100 nm)
meshwork randomly-woven 4 nm filaments
(Type IV collagen)
Reticular lamina: not always present, contains reticular
fibers & is made by underlying CT cells
Components of basement membrane
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Composition of Basal lamina
Type IV collagen
primarily in lamina densa structural; meshwork is physical filter
serves as attachment substrate with specific binding sites
Laminin
Cross-shaped multiadhesive glycoprotein primarily in lamina lucida
glue between cell membrane (integrins) and lamina densa (type IV collagen) has binding sites for integrins and Type IV collagen
Perlecan:A heparan sulphate containing proteoglycan
-It is highly negatively charged and thus helps regulate permeability of BL based
on charge
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Cytoskeleton-plasma membrane-basal lamina
Extracellular
matrix
Cytoplasm
Laminin
Type IV collagenIntegrins
Cellmembrane
Integrins: a family of trans-membrane linker proteins that functionas matrix receptors (fibronectin receptor, laminin receptor, collagen
receptor..)
Cytoskeleton(inside cell)
Plasma membrane
Basal lamina(outside cell)
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Functions of Basal lamina
Adhesion of epithelial cells to underlying CT (not justepithelial cells [external lamina] )
Selective permeability barrier (filter based on charge
and size [
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Surfacespecializationsof
epithelial cells
Epithelial cells have specializations at theirsurfaces that reflect the function of the cell at
that surface.1. Apical surface: microvilli, cilia, stereocilia
2. Lateral surface: intercellular junctions
3. Basal surface: basement membrane,junctional specializations, plasmamembrane interdigitations
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Microfilaments - composed of actin, ~7 nm in diameter
Intermediate filaments - composed of tissue-specific IFproteins (e.g., keratin, vimentin), ~10 nm in diameter
Microtubules - composed of tubulin, ~25 nm in diameter
Cytoskeleton (Review in J&C, p.43-48)
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Apical specializations
MicrovilliFinger-like processes extending from apical
surface (1-2 m in length)
Have a core of actin filaments (6 nm thin,microfilaments)
Very extensive in absorptive epithelium(increase surface area), called striatedborder or brush border
Bundles of actin filaments extend intoregion of cell called: terminal web
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Striated border
Terminal web
Small intestine, plastic section, toluidine blue
Simple columnar epithelium withstriated border
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Microvilli (TEM)
Terminalweb *
*
*
Mi ill T i l W b
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Microvillus-Terminal Web
Actin filamentsof the microvillusextend into the
terminal webJunqueira & Carneiro Fig. 4-8
Terminal web CellcoatMicrovilli
Actin
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Cilia
Long (5-10m) cytoplasmic extensions
Do NOT have a core of actin filaments
Have a complex arrangement ofmicrotubules (9+2) called axoneme
Tubulin is the major proteinwithin cilia
Facilitate flow of fluid over an epithelium
(tubular organ like trachea)
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SEM LM
Pseudostratified columnarepithelium with cilia
Cilia
TracheaH&E
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Cilia and basal bodies
Basal body
Junqueira & Carneiro Fig. 4-
cilia
Mi t b l
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Microtubules
K t S d (KS)
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Dynein armsNormal KS
Kartageners Syndrome (KS)Immotile-cilia syndrome
Autosomal recessive dissease (1/32000 live births in US)
Patients present with:chronic upper and lower respiratory tract disease(resulting from ineffective mucociliary clearance)
Sterility in males~50% display situs inversus (transposed viscera)
Biopsy examinations reveal abnormal and/or non-motile cilia
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Epididymis, H&E
Stereocilia
Long, immotile, branched microvilli that are found in themale reproductive tract
I t ll l J ti
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Intercellular Junctions
Lumen
BM
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Laboratory 2
Slide Preview
The Cell & Epithelium I
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Slide 94e: Epididymis (H&E)
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Golgi complex
Slide 94e: Epididymis (H&E)
This slide demonstrates a negatively stained Golgi complex
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Slide 94f: Epididymis, (Golgi complex, Osmium tetroxide fixed & stained)
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Osmium
Stained Golgi
Nucleus
Sperm
This slide demonstrates an Osmium stained Golgi complex
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*
*
*
Lumen withsperm
Golgi
nucleus
*
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Slide 65d, Liver, plastic (H&E)
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Slide 65d, Liver, plastic (H&E)
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Slide 65e, Liver, glutaraldehyde/OsO4 fixation, plastic, toluidine blu
Toluidine blue: metachromatic dye that stains glycogen magenta
RBC
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Slide 65e, Liver, glutaraldehyde/OsO4 fixation, plastic, toluidine blue
RBC
Mitochondria
Lipiddroplets
Nucleolus
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Liver hepatocyte(from EM packet)
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TEM of liver hepatocyte
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Slide 55d, Pyloric stomach (plastic, H&E)
Lumen
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Slide 55d, Pyloric stomach (plastic, H&E)
Endothelium
Mesothelium
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Slide 82a, thyroid, H&E
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Slide 82a, thyroid, H&E
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UF
DENTAL CLASS of 2011