Epithelial Tissue Flashcards by Nadarra Stokes

What is the biological hierarchy?

Cells->tissues->organs->systems

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Name four types of tissues.

Epithelial
Connective
Muscle
Nerve

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Where are epithelial cells found?

cover an external body cavity(e.g. Skin)
line an internal body cavity (peritoneal cavity) or tube (blood vessels/GI tract)
rest on basement membrane- can interface between epithelial and the underlying connective tissue

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Describe tissues. Not the ones you blow your nose on.

Tissues are made up of cells and associated extracellular materials that are structurally and functionally organized to perform specific functions

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Name some general characteristics of Epithelia.

Derived from all three primary germ layers: ectoderm, mesoderm, endoderm
Polarity: apical, lateral, and basal domain
Regeneration (stem cells)
Keratin is epithelial marker protein
Basement membrane interfaces with connective tissue
Produce the basal lamina component of the basement membrane
May be innervated
Most are avascular

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What are the two general categories based on numbers for cell layers?

Simple: a single cell layer
Stratified: two or more layers

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Name the shapes of cell in the most superficial cell layer of the epithelium.

Squamous (flat and thin)
Cuboidal (width=depth=height)
Columnar (height >width)

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What are the basic types of surface Epithelia?

Simple
-squamous: flat
-cuboidal: cube shape
-columnar: long and thin "like columns"
-pseudostratified: looks like more than one layer but isn't
Stratified
-includes the first four
-Transitional (urothelium)

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What are H& E stained sections? What is their purpose?

Hematoxylin(H) and Eosin(E) are used to differentiate the cell nuclei from cytoplasm

H binds to DNA and stains it blue
E binds to cytoplasm I proteins and stains it pink

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Describe simple cuboidal epithelium

The free apical surface of the cells face the lumen

The basal surface is in apposition to the connective tissue

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Describe simple squamous epithelium.

Endothelium is the simple squamous epithelium linking the blood vascular contents
Mesothelium is the simple squamous epithelium lining the internal cavities of the body

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Where can you find stratified columnar epithelium?

Very limited distribution

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Where can you find stratified cuboidal epithelium?

Very limited distribution

large ducts of salivary glands, pancreas
Excretory ducts of sweat gland in the skin

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Wet stratified squamous epithelium

Most superficial cells contain nuclei

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Dry stratified squamous epithelium

Nuclei are not present in superficial and juxtasuperficial layers
(Epidermis)

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What are some special configurations of Epithelia?

Pseudostratified epithelium
-trachea
Transitional epithelium (urothelium)
-lines lumen of the ureters and urinary bladder

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Describe transitional epithelium (urothelium).

Stratified

basal cells -> quite small
the cells lining the lumen are large

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Name Epithelial functions.

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Secretion
-columnar epithelium of the stomach and the gastric glands
Absorption
-columnar epithelium of the intestines and proximal convoluted tubules in the kidney
Transportation
-Respiratory epithelium and epithelium of oviduct
Protection
-stratified squamous epithelium of the skin
-urothelium of the bladder
Receptor function
-taste buds of the tongue
-olfactory epithelium of the nasal mucosa

Epithelia are polarized. Name the cell polarities.

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Apical domain: faces the external environment
Lateral domain: cell to cell contact
Basal domain: faces the basement membrane

The function of an epithelium depend on?

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It depend critically on apical cell surface specializations

What are the three apical domains?

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Microvilli
Stereocilia
Cilia

Describe microvilli and their function.

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They are fingerlike cytoplasmic projections on the apical surface of the cell. And their core is actin filaments.
They increase absorptive surface of the cell.
Microvilli
-core of actin filaments that are cross-linked by actin-bundling proteins: epsin, fimbrin, fascin

What is the terminal web?

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Horizontal network lies just below the base of the microvilli
-composed of actin filaments

Describe Stereocilia

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-immobile microvilli
-core:actin filaments
-may be unusually long Iike in epididymis
-not widely distributed among Epithelia
Limited to:
-the epididymis( male reproductive system)-absorptive function
-sensory (hair) cells of the inner ear-mechanoreceptors

Stereocilia vs microvilli

Stereocilia - different in size - presence of ezrin - absence of villin

Describe cilia

Common surface modifications with complex internal structure Axoneme: -internal microtubule (based structure) -extends from the basal body

What are the three basic categories of cilia?

Motile cilia Primary cilia: immobile Nodal cilia

What does the integrity of Epithelia depend on?

It depends critically on lateral cell surface specializations

What are the three intercellular complexes that make up the junctional complex?

``` Zonula occludens (ZO) Zonula adherens (ZA) Macula adherens (MA) or Desmosome ```

Nexus or Gap junctions are also called what?

Communicating junction

Describe Zonula Occludens (ZO) or tight junctions

Most apical component of the junctional complex Transmembrane protein: occludins and Claudins Function: to close the intercellular space Maintain the polarity of the cell

Define Zonula Adherens (ZA)

Below ZO Continuous band or beltlike configuration around the cell Transmembrane protein: cadherin Lateral adhesion between epithelial cells-by linking the actin cytoskeletons of adjacent cells

Describe macula adherens (MA) or desmosomes

Abundant in stratified Epithelia (skin) Transmembrane proteins: cadherins (desmocollin and desmoglein)-the intracellular segment binds to intermediate filaments Provide a localized spot-like junction between Epithelial cells

Describe gap junctions

``` Communicating junctions Allow the direct passage of signaling molecules between adjacent cells-> coordinate the functions of epithelium Transmembrane protein: Connexin -connexons (6 subunits) -gap junctions(12 subunits) ```

What does the hemidesmosome do?

Anchor the cell to the basement membrane Provide strong, stable adhesion between Epithelia and the connective tissue Transmembrane proteins: integrins

What does basal infolding do?

Morphologic modification of the basal cell surface Significantly increase the surface area of the casual cell domain Mitochondria are within the folds

Describe the basement membrane.

A non cellular layer- made up of - collageneous glycoproteins - non collageneous glycoproteins - proteoglycans * requires staying to be seen in light microscope*

What are the four basal domains?

Hemidesmosome Focal adhesions Basal infoldings Basement membrane

Basement Membrane vs Basal Lamina

``` Basement membrane (LM terminology) Basal Lamina (EM terminology) Basement Membrane = -basal Lamina (type 4 collagen) + -Reticular Lamina (type 3 collagen) ```

What are the functions of the basement membrane?

``` Structural support for the epithelium Compartmentalizations Filtration-selective barrier Polarity induction Tissue scaffolding-tissue regeneration after injury ```

Endocrine glands

The secretory products are released into the blood or surrounding tissues

Exocrine glands

Deliver their secretions to the epithelial surface

What is the clinical relevance?

Most cancers and tumors are epithelial origin | Malignant epithelial cells can move across the basement membrane in order metastasize

Epithelial Tissue Flashcards

(43 cards)