Epithelial Tissue - Histo Lec Flashcards Preview

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Flashcards in Epithelial Tissue - Histo Lec Deck (94):
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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

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Function of simple columnar

Absorption, Protection & Secretion

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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.

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Location of simple columnar

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

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When open to body cavities, simple columnar are called ______

mucous membranes

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Structure of pseudostratified

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

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Function of pseudostratified

Absorption and Secretion

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Features of pseudostratified

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

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Location of pseudostratified

Respiratory Linings & Reproductive tract

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Structure of stratified squamous

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

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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

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Also known as Urothelium

transitional epithelium

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Location of transitional epithelium

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

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Function of transitional epithelium

Allows stretching (change size)

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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.

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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

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

STRATIFIED CUBOIDAL

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rare
secretion and protection



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

STRATIFIED COLUMNAR

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often found between simple columnar epithelia and stratified squamous epithelia

STRATIFIED COLUMNAR

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

STRATIFIED COLUMNAR

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

STRATIFIED COLUMNAR

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

STRATIFIED COLUMNAR

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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

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

Polarity -

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

microvilli

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

microvilli

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

Stereocilia

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

Stereocilia

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

Stereocilia

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location of Stereocilia

epididymis & ductus deferens

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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:

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

Flagella:

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

THE LATERAL DOMAIN

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

JUNCTIONAL COMPLEX

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Three distinct components of junctional complex

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

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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)

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Junction for
Sealing off intercellular space

Tight Junctions (zonula occludens)

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Prevents digested macromolecules passing thru adjacent cells (impermeable barrier)

Tight Junctions (zonula occludens)

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Analogous to fascia occludens on adjacent endothelial cells lining capillaries

Tight Junctions (zonula occludens)

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

Tight Junctions (zonula occludens)

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Provides mechanical stability to group of epithelial cells



anchoring junctions

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Provide lateral adhesions between epithelial cells

anchoring junctions

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Cell Adhesion Molecules on both lateral and basal domain

anchoring junctions

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

a. Zonula Adherens aka belt desmosomes

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2. contains adhesion molecule “E-cadherin”

a. Zonula Adherens aka belt desmosomes

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

Extracellular Accessory Link/Ion (Ca2+)

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

Intracellular Link Protein

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



Macula Adherens “desmosome”

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

desmoplakins

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loop into and out of the desmoplakins

Keratin –

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– transmembrane linker glycoproteins between adjacent cells mediates the attachment

Desmogleins and desmocollins

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Allows selective diffusion of molecules; cell-cell communication





Gap Junctions Communicating junctions or nexus

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Is not a part of the junctional complex

Gap Junctions Communicating junctions or nexus

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Has pores for substance passage

Gap Junctions Communicating junctions or nexus

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Common also in CNS, cardiac muscle, and smooth muscle pass signals involved in contraction from one cell to another

Gap Junctions Communicating junctions or nexus

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Plaque-like(circular patch)entity composed of channels called “Connexons”

Gap Junctions Communicating junctions or nexus

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– six cylindrical connexins around a central channel

Connexons

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alter conformation to shut off communication between cells

Connexins -

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visible only by E.M.


Basal Lamina

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Consists of Matrix protein: type IV collagen, laminin, entactin + perlacan, and proteoglycans

Basal Lamina

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composition of matrix protein of basal lamina

type IV collagen, laminin, entactin + perlacan, and proteoglycans

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two zones of Basal Lamina
lies next to the plasma membrane

1. lamina lucida (lamina rara) –

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two zones of Basal Lamina
lies adjacent to the reticular lamina of deeper C.T.

2. lamina densa –

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Basal lamina + reticular lamina

Basement membrane

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Attachment of epithelial cells to underlying support tissue

Basement membrane

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Mediate adhesion of Epithelial cells to the underlying extracellular matrix

B. Hemidesmosomes

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Found in basal surface of basal cells (tracheal epithelium and stratified squamous).

B. Hemidesmosomes

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Dense cytoplasmic plaque linked via integrins to laminins in the basal lamina

B. Hemidesmosomes

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Type VII collagen from the basal lamina extend deeper into the underlying connective tissue and insert into plaques of type IV collagen.

B. Hemidesmosomes

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“Cell-to-Extracellular Matrix Junctions”

B. Hemidesmosomes

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