epithelium i (the first of four tissues)

8/14/2019 Epithelium I (the First of Four Tissues)

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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

epithelium i (the first of four tissues)

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