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26 Cards in this Set
- Front
- Back
Morphologic Polarity Domains
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Apical domain: luminal surface of the cell, common modifications include microvilli, and secretory vesicles in cells involved with the release of enzymes/mucins
Lateral domain: characterized by cell junctions - occluding, anchoring, communicating Basal domain: faces basement membrane, important for interactions with underlying (connective) tissues |
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Microvilli structure/function
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increase surface area for absorption
1 x 0.01 um core of actin filaments bound together with fimbrin and fascin, lateral anchoring proteins (myosin I) secure them apex formed by villin, which is the anchoring point for actin filaments |
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Stereocilia structure/function
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modified microvilli with and actin core
serve different roles such as absorption of fluid in the epididymis, or sensory reception in the cochlea |
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Cilia structure/function
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movement of substances through the lumen
core consists of 10 pairs of microtubules called the axoneme, which are attached to a centriole, called the basal body (9 triplets of mictrotubules without center) ~ 2-10 x .25 um |
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Cell Junctions
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Tight/Occluding junctions: occur towards the apical portion, represented by zonula occludens. Main purpose is blocking paracellular pathways in cells with secretory/absorptive roles
Anchoring Junctions: stability and mechanical strength to tissue, allowing for unified function. Connect cytoskeleton of adjacent cells, two types: zonula adherens, and macula adherens Communication/gap junctions: allow for diffusion of small molecules between cells through intercellular channels called connexons, which have 6 subunits, and occur in patches. Found most commonly in embryonic tissues, smooth muscle, and epithelia |
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Zonula Adherens structure
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connect actin filaments of two cells. consist of:
- Actin-binding proteins - Peripheral protein - Transmembrane link protein (cadherin family *mutations commonly found in cancer)` |
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Macula Adherens structure
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called desmosome: spot-like junctions connecting the intermediate filaments of two cells. Common in epidermis of the skin, as it provides mechanical strength.
-Intracellular plaque: desmoplakin, filaments pass through the plaque -Transmembrane proteins: from the cadherin family * Pemphigus: disease in which antibodies disrupt the desmosome junctions from forming, results in blistering, as fluid entering the intercellular space pulls apart faulty junctions |
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Basal domain features
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Basal lamina: polymers for a sheet-like membrane (usually a fiber) formed at the most external layer of the membrane
Reticular lamina: connective tissue layer just deep to the basement membrane. composed of collagen fibers |
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Basal anchoring junctions
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Focal adhesions: attach actin cytoskeleton of a cell to the extracellular matrix
- Actin-binding proteins - Peripheral protein - Transmembrane protein of the integrin family, not cadherin Hemidesmosomes: connects intermediate filaments of cytoskeleton and extracellular matrix - Intracellular plaque: intermediate filaments end on the plaque - Transmembrane proteins (integrin family) |
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Epithelial Classifications
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- Layers
Simple: single cell layer Pseudostratified: all cells rest on basement membrane, but not all reach the apical surface Stratified: more than one layer of cells - Shape Squamous: flattened Cuboidal: width and height is roughly the same (nucleus appears circular) Columnar: height is greater than transverse diameter - Apical modifications Ciliated Non-ciliated |
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Simple squamous epithelium
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lining of the vascular system, body cavities, parietal layer of Bowman's capsules, and alveoli of the lung
functions as a barrier, or the diffusion of gases endothelium: vasculature mesothelium: covers internal organs cavities. Pleural, pericardial, and peritoneal |
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Simple cuboidal epithelium
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found in:
- walls of ducts of various glands - in the kidney tubules - germinal epithelium of ovary - thyroid follicles Main functions: Barrier (ducts) Secretion (thyroid) Absorption (kidney) |
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Simple columnar epithelium
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two surface modifications:
microvilli: found in non-ciliated cells in the lining of the gastrointestinal tract, and walls of the gallbladder cilia: found in ciliated cells lining the oviduct Main functions include absorption, secretion, lubrication, and transport |
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Pseudostratified columnar epithelium
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sub-types
ciliated: found in the epithelium of the respiratory tract. Metaplasia (cells change into another type e.g. smokers). Function to remove mucus from the lungs non-ciliated: found in the epididymis, featuring immobile stereocilia that are used for absorption |
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Stratified squamous epithelium
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sub-types
Keratinized: dead, cornified layer on surface; found in epidermis of the skin Non-keratinized: found in the oral cavity, esophagus, and vagina. Lacking the dead layer of keratin on surface |
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Stratified cuboidal epithelium
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Somewhat rare, occurs in ducts of various glands e.g. sweat glands of the skin. Two layers of cuboidal cells, serves as barrier and conduit.
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Stratified columnar epithelium
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found in larger ducts of some glands: parotid, and submandibular salivary glands. Basal layer is cuboidal, while the surface is columnar. Serves as barrier and conduit.
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Transitional epithelium
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called urothelium; found lining the urinary system, the cells in this tissue exist in every shape classification, and the surface layer subsists of binucleated, "dome" shaped cells.
Main feature is the ability to greatly stretch itself, and return to original shape when the organ is dilates/contracts. |
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Glandular epithelium types
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formed by invaginated epithelial tissues. target of their secreted materials is the main distinction:
Endocrine: secrete product into intercellular space, which diffuses into the blood. Lacking a duct. Exocrine: secrete products into ducts, that remain connected with original epithelium. Organized as tubules, or acini. |
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Exocrine gland mechanisms of secretion
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merocrine glands: secretory product is released from membrane-bound vesicles on the apical surface; 3 types.
apocrine glands: secretion involves pinching the apical cytoplasm into secretory vesicles (e.g. mammary glands, where large lipid droplets are added to milk). holocrine glands: involves the entire cell; accumulates secretory product, and then undergoes apoptosis to release products (e.g. sebaceous glands). |
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Unicellular gland features
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individual secretory cells scattered throughout non-secretory epithelium (e.g. Goblet cells in the GI tract).
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Multicellular glands
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multicellular glands form different types of structures (tubular/acinar) that increases the surface area.
The terminal portion is known as the secretory portion, whereas the connection between that and the surface is called the duct |
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secretory part classifications
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Acinar: shaped like a flask, also called alveolar; can be simple or branched
Straight tubular glands: unbranched tube. simplest organization (e.g. Crypts of Lieberkuhn of the GI tract). Branched tubular glands: uncommonly occurring glands. Usually found in digestive system (pyloric glands of the stomach). Coiled tubular glands: coiled tube-shaped structure (e.g. sweat glands). tubuloalveolar: secretory tube-shape ends in a flask-shaped dilation. |
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Duct classifications
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Simple: unbranched
Compound: - compound alveolar gland: common in exocrine glands. flask-shaped secretory terminus, and branched ducts (Parotid salivary glands, and exocrine pancreas). - compound tubuloalveolar gland: highly branched duct system, with some ending as tubules and others ending as alveoli (Submandibular salivary gland, prostate, and mammary glands). |
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Myoepithelial cells
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contractile cells found within some glands between basal lamina, and secretory portion of glands and ducts. Contractile proteins (e.g. myosin) cause expulsion of product from gland (e.g. sweat, salivary, mammary glands).
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Cancer of epithelium
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carcinogens commonly reach these surfaces. Principal types:
Carcinoma - derived from barrier epithelium Adenocarcinoma - derived from glandular epithelium |