State the functions of the epithelia. List where they are found.

Functions of Epithelia: SPACES

1. Secretion (production of useful materials)

2. Protection

3. Absorption

4. Contractility

5. Excretion (expulsion of garbage)

6. Sensory perception (smell, taste, hearing, vision)

Derives from the ectoderm. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies.

Explain the concept of cell "polarity" in morphologic & functional terms. Give examples. Explain how membrane modifications contribute to cell polarity.

Polarity: apical and basolateral regions are segregated, usually by tight junctions. Each region contains membrane modifications and membrane proteins that are functionally different. Cytoplasmic contents may also be limited to either apical or basal poles.

Describe basement membrane structure and state ts functions. Name and describe each layer, listing specific or unique components. Identify the components in photographs and diagrams.

A LM structure that anchors down the epithelium to its loose connective tissue underneath by focal adhesions and hemidesmosomes. Other functions include induction of polarity, filtration of material thru ECM, participation in cellular regeneration.

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Basal lamina: type lV collagen, laminin,
perlecan heparan sulfate, fibronectin
Reticular lamina: type III collagen, type VII collagen (attaches to reticular fibers), fibrillin (attaches to elastic fibers)

List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

tight junctions

Tight junctions (zonulae occludens): seal adjacent epithelial cells in a narrow band

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Functions:

• They prevent the diffusion of molecules and ions through the space between cells. 
• They block the movement of integral membrane proteins  between the apical and basolateral surfaces of the cell. Thus the special functions of each surface, for example receptor-mediated endocytosis at the apical surfac exocytosis at the basolateral surface can be preserved.

Composed of claudins and occludins.

Assoc. w/ intracytoplasmic proteins (ZO proteins), which anchor to actin cytoskeleton.

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Define: CAMs

Ca²⁺ dependent - cadherins, integrins, selectins

Ca²⁺ indepedent - Immunoglobulin (Ig) Superfamily CAM (Ig-CAMs)

Define: cadherins

CAlcium - Dependent adhesion

Cadherins - strong, long-term adhesion, e.g. E-cadherin,

interaction: homophilic

Ca²⁺ - required

Bind to actin via anchoring proteins (catenins)

Define: selectins

selectins: transmembrane proteins that bind to specific carbohydrates (selective); they mediate transient cell-cell adhesion

interaction: heterotypic

Calcium: required

Bind to actin via anchoring proteins

Define: N-CAMs

NCAMs - neural cell adhesion molecules, part of the IgSF-CAMs, which are low affinity, but have multiple binding, calcium independent, and have Ig-like loops

Define: ICAMs

ICAM - intercellular cell adhesion molecule, that is part of the IgSF-CAM, that do not require calcium, have low affinity, but multiple binding sites, and have Ig-like loops

ICAM -1 on endothelial cell binds integrin on WBC (heterophilic)

Define: catenin

catenin - proteins found in complexes with cadherin cell adhesion molecules, binds cadherins to actin

Define: integrins

integrins - low affinity, transient adheison, with strenth in numbers nad density; composed of α and β subunits.

interaction: heterophilic (cell-ECM, or cell-β2)

Ca²⁺ : required, can use another divalent cation (Mg²⁺)

Bind to actin via the β subunit.

Distinguish homophilic interactions from heterophilic interactions, and identify the adhesion molecules involved in each. List adhesion molecules that are calcium-dependent and those that are calcium-independent.

Homophilic: cadherins, IgSF-CAMs

Heterophilic: integrins, selectins, IgSF-CAMs

Calcium-dependent - cadherins, selectins, integrins

Calcium-indepedent - IgSF-CAMs

Explain how the ECM can influence the cytoskeleton, and vice versa.

Describe the structure & function of microvilli and stereocilia.

Structure: finger-like projections with an actin core, which increase surface area

Scattered, individual, variably sized & shaped microvilli: mesothelium, hepatocytes, distal renal tubules

uniform, closely packed arrays that appears as "brush-border" or "striated border": absorptive enterocytes, proximal renal tubule cells

Unusually long microvilli, often branched, may be called "stereocilia"

Functions: absorption, secretion, cellular adhesion, and mechanotransduction

Describe the structure & function of cilia.

Structure: 9+2 microtubule arrangement anchored in a basal body, which has 9 doublets surrounding 2 singlets, each doublet has dynein arms that form temporary cross links with adjacent doublet allowing movement (ATP req)

Function: sensory cellular antennae, and movement

Describe basolateral plasma membrane infolding (plicae).

basal domain infolds, promoting transport of materials from the cell into the interstitium.

if between cells, then increase cell-cell transport;

increased plasma membrane will stain pink, and produce pink lines in LM "striations"

List the classifcation of the different types of covering and lining epithelia. State where each type is commonly found. Describe how these epithelia are provided with nutrients and nerves. Describe the regenerative capacity of each type. Identify each type in photographs and diagrams: stratified squamous

stratified squamous: found in skin, oral cavity, esophagus, anus, vagina, lips externally

may be keratinized (skin, external lips [cross-linked]) or

non-keratinized (oral cavity, esophagus, anus, vagina, internal lips)

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Describe the classification of glandular epithelia with examples. Define and distinguish between exocrine, endocrine, and paracrine/autocrine types of secretion.

Exocrine: secrets onto a surface or into a duct, e.g. sweat glands, salivary glands, mammary glands, stomach, liver, pancreas. 

•merocrine: secretory product is packaged in membrane bound vesicles released by exoctyosis, e.g. Salivary glands, Pancreatic glands

•apocrine - some cytoplasm is lost in the secretion process, e.g. mammary gland (fat online), casein is mesocrine

•holocrine: the entire cell is the secretion; sebaceous glands; sperm

Endocrine: secrets into blood (no ducts), e.g. thyroid, parathyroid, pituitary, etc.

•paracrine: type of endocrine, where target cell is near, e.g. Growth factor and blood clotting factors, responses to allergens, tissue repair, the formation of scar tissue,

•autocrine: type of endocrine, where it binds to itself, e.g. cytokine interleukin-1 in monocytes,

Classify, describe, & distinguish between different structural patterns of glands (simple vs. compound, straight, coiled branched, etc.) Appropriately label diagrams of each type. Give examples of each type.

structural features of ducts:

simple vs. compound: 1 duct vs. more than one duct

straight vs. coiled: self-explanatory

branched vs. unbranched: how many come off the main duct

acinar: shaped like alveolar sac (raspberries)

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Describe the secreted product:

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What type of secretion product is this?

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What type of secretion product is this?

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What type of secretion is this?

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What type of secretion is this?

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What type of secretion is this?

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What type of secretion is this?

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Define & describe myoepithelial cells. Based on their function, predict which tissues are most likely to have myoepithelial cells.

Discuss the concept that epithelia derive from all three embryonic germ layers.

• from ectoderm (e.g., the epidermis);
• from endoderm (e.g., the lining of the GI tract);
• from mesoderm (e.g., the inner linings of body cavities)

Discuss the need for ongoing epithelial cell renewal and its implications.

Describe characteristics common to most epithelia and distinctive from structural tissues.

Disctinct features of Epithelial cells: BARF'DP

1. Basement membrane - separate epithelial cells from adjacent extracellular matrix (MAN exceptions: muscle, adipocytes, and nerve)

2. Aggretations of cohesive groups

3. Regeneration - provided by progenitor cells, allowing rapid recovery but also higher risk for cancer

4. Firmly attached, multiple cell-cell adhesions

5. Diffusion of nutrients, opp. to blood vessels (exception: ear)

6. Polarity

List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

adherent junctions (zonula adherens)

Adherens junctions - Cell-Cell junctions that provide strong mechanical attachments between adjacent cells and cell signaling

[image]Built from:

• CAdherins — transmembrane proteins (shown in red) whose extracellular segments bind to each other and whose intracellular segments bind to

Linker proteins: catenins (yellow). Catenins are connected to F actin microfilaments.

Cytoskeletal connection: microfilaments

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Right: ZA, Left: Desmosomes

List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

desmosomes (maculae adherens)

Desmosomes - (Cell-Cell) localized patches that hold two cells tightly together. They are common in the skin.

Built from: cadherins

Cytoskeletal attachment intermediate filaments of keratin in epithelia, or desmin in cardic.

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List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

Focal Adhesions/focal contacts

Focal adhesions (Cell-ECM) - connect to actin and allow focal attachments as non-epithelial cells to migrate through ECM. Attach muscle fibers to tendon. Also for signal dectiona and transduction. Extraceullar domains bind to ECM (laminin, fibronectin)

Built from: integrins

Cytoskeletal connection: microfilaments (F-actin)

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List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

hemidesmosomes

Hemidesmosomes - (Cell-ECM) similar to desmosomes but attach epithelial cells to the laminin basal lamina ("basement membrane" – View) instead of to each other.

Build of: integrins

Cytoskeletal connection: intermediate filaments

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List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

Gap Junctions

Gap junctions (cell-cell) - intercellular channels some 1.5–2 nm in diameter. These permit the free passage between the cells of ions and small molecules (up to a molecular weight of about 1000 daltons). Connect cells and transmit signals.

Made of: hexamer of connexins->connexon (channel)

Connexons can be homomeric, or heteromeric and homotypic or heterotypic. "hemi-channels"-> half channel formed from each side of the connecting cells.

Examples:

• The action potential in heart (cardiac) muscle flows from cell to cell through the heart providing the rhythmic contraction of the heartbeat.
• At some synapses in the brain, gap junctions permit the arrival of an action potential at the synaptic terminals to be transmitted across to the postsynaptic cell without the delay needed for release of a neurotransmitter.
• As the time of birth approaches, gap junctions between the smooth muscle cells of the uterus enable coordinated, powerful contractions to begin.

Regulators: Ca²⁺, pH, extracellular ligands-> PKA ->phosphorylation of connexins

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List and describe the major cell junctions and adhesions, including features in common and distinguishing features. State the function of each. Describe the characteristic structural components of each and correlate each with its ulturalstructural appearance, when appropriate:

Junctional Complex

Junctional Complex: combination of cell junctions found in columnar cell mucosa of GI tract

Made of: ZO, ZA, MA (from apically to basally)

tight junctions, adherens, desmosomes

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List the classifcation of the different types of covering and lining epithelia. State where each type is commonly found. Describe how these epithelia are provided with nutrients and nerves. Describe the regenerative capacity of each type. Identify each type in photographs and diagrams: simple squamous

simple squamous: endothelium (lines interior of blood vessels), and mesothelium (interior cavities and covers organs within those cavities): pleura (thoracic cavity), peritoneum (abdominal cavity including the mesentery) and pericardium (heart sac)

Also: type I pneumocytes (lungs) and thin loop of Henle cells (kidney)

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List the classifcation of the different types of covering and lining epithelia. State where each type is commonly found. Describe how these epithelia are provided with nutrients and nerves. Describe the regenerative capacity of each type. Identify each type in photographs and diagrams: simple columnar

found in: intestinal lining, gall bladder

functions: absorptive and secretory functions

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List the classifcation of the different types of covering and lining epithelia. State where each type is commonly found. Describe how these epithelia are provided with nutrients and nerves. Describe the regenerative capacity of each type. Identify each type in photographs and diagrams: pseudostratified epithelium

function: secretion or absorption. If a specimen looks stratified but has cilia, then it is a pseudostratified ciliated epithelium--stratified epithelia don't have cilia.

pseudostratified, ciliated columnar is the most common = respiratory epithelium

non-ciliated = male vas deferens

ones with stereocilia are located in the epididymis

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List the classifcation of the different types of covering and lining epithelia. State where each type is commonly found. Describe how these epithelia are provided with nutrients and nerves. Describe the regenerative capacity of each type. Identify each type in photographs and diagrams: urothelium (transitional epithelium)

Found exclusively in the urinary tract: bladder, ureters, renal calyces

surface "umbrella" of cells store membrane w/in cytoplasm, expanding/decreasing in size (think bladder)

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Describe the gland strcture:

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Describe the gland strcture:

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Describe the gland strcture:

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Describe the gland strcture:

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Describe the gland strcture:

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Describe the gland strcture:

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Describe gland strcture:

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Describe the gland strcture:

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