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Microanatomy
Epithelium
64
Medical
Professional
09/04/2008

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Term
Definition of epithelium
Definition
-tissue that covers the outer and inner surfaces of the body, with the exception of the joint cavities and anterior surface of iris
-continuous sheet that forms a boundary between underlying connective tissue and the environment
Term
Location of epithelium
Definition
1. exterior surfaces of body (skin)
2. internal closed cavities (abdominalm thoracic, pericardial)
3. body tubes that extend to exterior (gastrointestinal, respiratory, genitourinary)
4. glands
5. vascular system
6. receptors of certain sensory organs
Term
Functions of epithelium
Definition
1. protection
2. selective barrier for exchange
3. secretion
4. absorption
5. sensory reception
Term
Characteristics of epithelium
Definition
1. sheets of cells
2. no extracellular elements between them
3. specialized contacts between adjacent cells
4. polarized with apical and basal domains
5. avascular -receives nutrients from capillaries below BM
6. stem cells-can renew
Term
Types of epithelium
Definition
1. simple or stratified
2. squamous, cuboidal, columnar

*in stratified, only shape of cells on surface layer used to categorize
Term
simple squamous epithelium
Definition
1. lining of vascular system (endothelium)
2. lining of peritoneal, pleural, and pericardial cavities (mesothelium)
3. pulmonary alveoli
Term
simple cuboidal epithelium
Definition
1. proximal and distal tubules of kidney
2. glandular ducts
3. ovarian surface
Term
Function of simple squamous epithelium
Definition
barrier, exchange, lubrication
Term
Function of simple cuboidal epithelium
Definition
absorption, secretion, barrier
Term
simple columnar epithelium
Definition
1. stomach
2. small intestine
3. large intestine
4. gallbladder
Term
Function of simple columnar epithelium
Definition
secretion, absorption
Term
stratified squamous epithelium
Definition
1. vagina
2. oral cavity
3. esophagus

1,2,3 - non-keratinized

4. skin (keratinized)
Term
Function of stratified squamous epithelium
Definition
barrier, protection
Term
stratified cuboidal epithelium
Definition
1. sweat gland ducts
2. large ducts of exocrine glands
Term
Functions of stratified cuboidal epithelium
Definition
barrier, conduit
Term
stratified columnar epithelium
Definition
1. male urethra
2. conjunctiva
3. excretory ducts of exocrine glands
Term
Function of stratified columnar epithelium
Definition
barrier, conduit
Term
pseudostratified epithelium
Definition
*touches BM but looks stratified
1. trachea and bronchi (with goblet cells)
2. epididymis (with stereocilia)
3. olfactory epithelium (neuroepithelium)
Term
Functions of pseudostratified epithelium
Definition
secretion, absorption, conduit
Term
Transitional epithelium
Definition
stratified epithelium

lines urinary tract only

pillowy appearance
Term
Functions of transitional epithelium
Definition
barrier, distensible properties
Term
Neuroepithelium
Definition
sensory function
1. taste buds
2. olfactory epithelium
3. retina (rods and cones)
4. inner ear
Term
myoepithelial cells
Definition
branched, stellate cells containing actin filaments
contractile
expel contents of exocrine glands
Term
endocrine gland
Definition
secretes products into the blood and are ductless
Term
exocrine gland
Definition
secretes product onto epithelial surface usually via tubular ducts
Term
goblet cell
Definition
unicellular gland that secretes mucin, which upon hydration form mucus. scattered in intestine and respiratory system
Term
multicellular gland
Definition
develop when epithelia invade underlying connective tissue
consists of secretory portion and duct portion.
Term
Kinds of multicellular glands
Definition
1. simple (unbranched) or compound (branched)
2. tubular (tube) or alveolar/acinar (flasklike)
Term
Intestinal glands of Liberkuhn
Definition
simple tubular gland
Term
sweat gland
Definition
simple coiled tubular gland
Term
glands of stomach and uterus
Definition
simple tubular branched gland
Term
sebaceous glands of skin
Definition
simple acinar gland
Term
glands of oral cavity
Definition
compound tubular gland
Term
exocrine pancreas
Definition
compound alveolar gland
Term
mammary gland
Definition
compund tubuloacinar gland
Term
serous cells
Definition
1.synthesize and secrete proteins
2. basophilic (stain purple)
3. present in exocrine pancreas and salivary glands
Term
mucus-secreting cells
Definition
1.synthesize and secrete mucin
2. plae staining mucus granules with flat nuclei at base.
3. present in salivary glands, respiratory tract, and GI tract
Term
merocrine secretion
Definition
exocytosis of secretory vesicle with no loss of cellular material (most exocrine and endocrine glands)
Term
apocrine secretion
Definition
exocytosis with loss of cytoplasm and membrane (mammary gland for lipid component of milk)
Term
holocrine secretion
Definition
secretion product is shed with entire cell (sebaceous gland--apoptosis)
Term
myoepithelial cells
Definition
1.star-shaped cells that lie between glandular epithelium and basal lamina
2.communicate via gap junctions to coordinate contraction which squeezes contents of gland out
Term
Cilia
Definition
1. motile, hairlike structures
2. 5-10 um, 0.2 um diameter
3. trachea, bronchi, oviducts
4. 9+2 microtubule arrangement
5. dynein act as molecular motor
5. anchored to basal bodies in cytoplasm
Term
microvilli
Definition
1. nonmotile, cytoplasmic fingerlike projections
2. 1-2 um, 0.08um diameter
3. maximize apical surface area
4. brush border in intestine and kidney tubules
5. made of actin filaments
6. attached to terminal web (horizontal network of myosin II and actin in apical cytoplasm)
Term
stereocilia
Definition
1. branched, nonmotile microvilli in epididymus, vas deferens, and ear
2. 100 um long
3. can be connected to neighbors by cytoplasmic bridge
4. responsible for resporption of fluid secreted by testis.
5. part of sensory apparatus of ear
Term
Kartagener's syndrome
Definition
1.immotile cilia syndrome--affect dynein arm proteins
2. difficulty moving mucus, infertility
Term
Functions of intercellular junctions
Definition
1. adherence of adjoining cells
2. provide a barrier for diffusion between cells
3. communication
Term
Zona occludens (tight junction)
Definition
1. a belt-like barrier device around lateral portion of cell
2. separate apical surface from basolateral environment
3. blocks paracellular (between cell) pathway
Term
ZO-1,2,3
Definition
1.proteins that bind transmembrane proteins of tight junctions to actin cytoskeleton
2. target of CHOLERA toxin
Term
zona adherens
Definition
1. adhesive device beneath zona occludens
2. dense plaque of proteins (actinin and vinculin) bind to ACTIN filaments in terminal web
3. 15-20 nm space with transmembrane protein (e-cadherin) that requires Ca++ to maintain junctional integrity
Term
macula adherens/desmosome
Definition
1. spot weld found below zona adherens
2. cytoplasmic side has plaque with 10 nm intermediate filaments (tonofilaments) attached.
3. 20-30 nm intercellular space with adhesive glycoproteins
4. effectively crosslink cytoskeletons of adjacent cells--distribute mechanical stress
Term
hemidesmosomes
Definition
1. half desmosomes
2. anchor cytoplasmic intermediate filaments
3. attach cell to BM by integrins
Term
focal adhesion
Definition
most epithelial cells attach cytoskeletal ACTIN filaments to BM via these
Term
junctional complex (terminal bar)
Definition
zona occludens, zona adherans, macula adherens
Term
gap junctions (nexus)
Definition
1. non-adhesive connections between epithelial cells
2. allows for communication
3. separated by 2 nm gap bridged by connexons
4. connexon formed from 6 connexin proteins
5. allow exchange of ions, cAMP, GMP, and hormones (<1500 MW)
6. high Ca++ cause closure
7. functional coordination of smooth and cardiac muscle
Term
lateral folds
Definition
1. prominent in epithelia that transport fluid rapidly
2. intestine, gallbladder, kidney
Term
basal folds
Definition
1. prominent in epithelia that transport fluid rapidly
2. proximal and distal kidney tubules and striated ducts of salivary glands
Term
parts of basal lamina
Definition
1. basal lamina
a. lamina lucida
b. lamina densa
2. reticular lamina
Term
components of lamina densa
Definition
laminin, fibronectin, type IV collagen, heparin sulfate proteogylcans
Term
integrins
Definition
part of lamina lucida that are attach fibronectin and laminin to the cell membrane
Term
basal lamina origin
Definition
secreted by epithelium
Term
reticular lamina origin
Definition
secreted by underlying connective tissue
Term
reticular lamina components
Definition
reticular fibers--fibrils of type III collagen
type VII collagen attaches basal lamina to reticular lamina
Term
basement membrane of glomeruli and lung alveoli
Definition
share common lamina densa with lamina rara on both sides
Term
functions of basement membrane
Definition
1. support epithelium
2. attachment of epithelium to connective tissue
3. separation of epithelium from connective tissue
4. selective permeability barrier
5. polarity
6. affect signal transduction
7. regulate cell proliferation and differentiation via growth factors
8. scaffold for cell migration
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