Epithelial Tissue - Histo Lec Flashcards by Carmina Mislang

aggregates or groups of cells organized to perform one or more specific functions.

tissues

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Four basic types of tissues:

– covers body surfaces, lines body cavities and forms glands

Epithelium

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Four basic types of tissues:

underlies or supports the other three basic tissues, both structurally and functionally.

Connective

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Four basic types of tissues:

made up of contractile cells and is responsible for movement

Muscle

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Four basic types of tissues:
receives, transmits, and integrates information from outside and inside the body to control activities of the body.

Nerve

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Avascular tissues

epithelial tissue

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Covers body surfaces,

As receptors for the special senses

epithelial tissue

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lines body cavities,

epithelial tissue

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and constitutes glands;

epithelial tissue

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Sheet of cells lying close together

epithelial tissue

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Continuous sheet w/ little extracellular matrix

epithelial tissue

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Function of Epithelial Tissue

a. Diffusion of O2 and CO2 across the epithelial cells of lung alveoli and capillaries

Transcellular Transport

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Function of Epithelial Tissue

b. Carrier-protein mediated transport of amino acids

Transcellular Transport

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Function of Epithelial Tissue

c. Vesicle-mediated transport of IgA and other molecules

Transcellular Transport

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Function of Epithelial Tissue

Occurs via endocytosis and pinocytosis (columnar epithelium of the intestines and proximal convoluted tubules in the kidney)

Absorption

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Function of Epithelial Tissue

Occurs via exocytosis (different glands produce perspiration, oil, digestive enzymes and mucus)

Secretion

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Function of Epithelial Tissue

From abrasion and injury by the epithelial layer of the skin and gall bladder.

Protection

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Function of Epithelial Tissue

Lining of Kidney tubules filtering wastes from blood plasma

Filtration

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Structure of simple squamous

Single Layer of flattened cells

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Function of simple squamous

Absorption, and filtration

Not effective protection – single layer of cells

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Location of simple squamous

Walls of capillaries, air sacs in lungs
Form serous membranes in body cavity
Mesothelium (lining of peritoneum and pleura )
Endothelium (lining of blood vessels)

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Structure of simple cuboidal

Single layer of cube shaped cells

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Function of simple cuboidal

Secretion and transportation in glands, filtration in kidneys

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Location of simple cuboidal

Glands and ducts (pancreas & salivary), kidney tubules, covers ovaries

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Structure of simple columnar

Elongated layer of cells with nuclei at same level

Function of simple columnar

Absorption, Protection & Secretion

Special Features of simple columnar

Microvilli, finger-like projections of the apical surface, increase surface area for absorption Goblet cells, single cell glands, produce protective mucus.

Location of simple columnar

Linings of entire digestive tract, gall bladder, uterus, kidney tubules

When open to body cavities, simple columnar are called ______

mucous membranes

Structure of pseudostratified

Irregularly shaped cells with nuclei at different levels – appear stratified, but aren’t. All cells reach basement membrane

Function of pseudostratified

Absorption and Secretion

Features of pseudostratified

Goblet cells produce mucus | Cilia – hair-like projections; move fluid over cell surface or confer cell motility (larger than microvilli)

Location of pseudostratified

Respiratory Linings & Reproductive tract

Structure of stratified squamous

Several layer of cells with : a. flattened cells (upper layer); b. polyhedral cells (middle layer) c. columnar cells (basal layer).

Types of stratified squamous

Stratified squamous non-keratinizing – flattened surface cells retain their nuclei; found in vagina, esophagus and tongue. Stratified squamous keratinizing – flattened surface cells lose their nuclei, form a layer of dead keratinized cells; found in the skin

Also known as Urothelium

transitional epithelium

Location of transitional epithelium

Renal pelvis, urinary bladder, ureters & proximal 1/3 of urethra.

Function of transitional epithelium

Allows stretching (change size)

Structure of transitional epithelium

Many layers Superficially located umbrella-shaped cells; pyriform cells in the middle layer and columnar or polyhedral cells in the most basal layer.

``` rare cube-shaped commonly cells make up two layers protection of larger ducts: pancreas, salivary, and sweat glands mammary gland in the breast ```

STRATIFIED CUBOIDAL

Basal cells are typically cuboidal with surface cells either columnar or cuboidal in appearance

STRATIFIED CUBOIDAL

rare secretion and protection intestinal lining - ciliated to help move nutrients and increase absorption, also protects against pathogens/bacteria

STRATIFIED COLUMNAR

often found between simple columnar epithelia and stratified squamous epithelia

STRATIFIED COLUMNAR

found near salivary glands - cell lining protects the salivary duct, goblet cells found between the cells

STRATIFIED COLUMNAR

found in vas deferens where it protects and aids in secretion of glands

STRATIFIED COLUMNAR

also form layers in ocular conjunctiva and the linings of the pharynx, anus, uterus, urethra

STRATIFIED COLUMNAR

Three principal characteristics of epithelial tissue

a. Closely apposed and adhere to one another by means of specific cell-to-cell adhesion molecules (cell junctions) b. Functional and morphologic polarity: three morphologic domains c. Basement membrane

refers to the asymmetric organization of different aspects of the cell including the cell surface, intracellular organelles and the cytoskeleton

Polarity -

Features of Apical Surface of Epithelium Finger-like extensions of the plasma membrane of apical epithelial cell Increase surface area for absorption

microvilli

Features of Apical Surface of Epithelium | found in small intestine, kidney tubules

microvilli

Features of Apical Surface of Epithelium | Does not conform to the function of cilia

Stereocilia

Features of Apical Surface of Epithelium | Longer than microvilli but less motile

Stereocilia

Features of Apical Surface of Epithelium | Does not conform to the function of cilia

Stereocilia

location of Stereocilia

epididymis & ductus deferens

Features of Apical Surface of Epithelium (eg.) respiratory tubes Whip-like/hair-like projections, motile extensions Moves mucus, etc. over epithelial surface 1-way (moves mucus upward but not downward)

Cilia:

Features of Apical Surface of Epithelium (eg.) spermatozoa Extra long cilia Moves cell

Flagella:

Contain specialized junctions that contain cell adhesion molecules (CAMs) and restrict movement of materials into and out of lamina.

THE LATERAL DOMAIN

Membrane-associated structures that functions in cell-to-cell attachment of columnar epithelial cells.

JUNCTIONAL COMPLEX

Three distinct components of junctional complex

1. Tight Junctions (zonula occludens) 2. Anchoring Junctions a. belt desmosomes, zonula adherens b. desmosome (macula adherens)

Formed by the fusion of the outer leaflets of cell’s plasma membrane ex . Active transport-Prevents back-diffusion of transported substances

Tight Junctions (zonula occludens)

Junction for | Sealing off intercellular space

Tight Junctions (zonula occludens)

Prevents digested macromolecules passing thru adjacent cells (impermeable barrier)

Tight Junctions (zonula occludens)

Analogous to fascia occludens on adjacent endothelial cells lining capillaries

Tight Junctions (zonula occludens)

Has 4 transmembrane – tightly attach cellular membrane | -aid in attachment

Tight Junctions (zonula occludens)

Provides mechanical stability to group of epithelial cells

anchoring junctions

Provide lateral adhesions between epithelial cells

anchoring junctions

Cell Adhesion Molecules on both lateral and basal domain

anchoring junctions

1. surrounds the entire perimeter of epithelial cells just basal to the tight junction

a. Zonula Adherens aka belt desmosomes

2. contains adhesion molecule “E-cadherin”

a. Zonula Adherens aka belt desmosomes

feature of Zonula Adherens aka belt desmosomes | mediates attachment of E-cadherin

Extracellular Accessory Link/Ion (Ca2+)

feature of Zonula Adherens aka belt desmosomes | attached to the transmembrane link protein

Intracellular Link Protein

Localized spot-like junction between epithelial cells | Each has intracellular plaque

Macula Adherens “desmosome”

dense plaque of intercellular which consists of several link protein attachment proteins on cytoplasmic surface of each opposing cell.

desmoplakins

loop into and out of the desmoplakins

Keratin –

– transmembrane linker glycoproteins between adjacent cells mediates the attachment

Desmogleins and desmocollins

Allows selective diffusion of molecules; cell-cell communication