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45 Cards in this Set

  • Front
  • Back
epithelia cover outer surfaces and line inner surfaces (cover all free surfaces) thruout the body except in what 2 places?
1) synovial joint cavities
2) anterior surface of the iris
Places where epithilium lies and specific organs/body parts with each surface (6)
1) Exterior Surfaces of the body (skin) - mesothelium
2) Internal Closed Cavities of the body (abdominal, thoracic and pericardial)
3) those Body Tubes that communicate w/ the exterior (gastrointestinal, respiratory, and genitourinary tracts)
4) the Glands, both exocrine (sweat, saliva, liver, overall fluid) and endocrine (thyroid, adrenal, overall hormones)
5) the Vascular System
6) the Receptors of Certain Sensory Organs - taste buds, olfactory epithelium, retina, auditory/vestibular system (aka Neuroepithelium)
An epithelium may have any of several functions, depending on its location in the body (5)
1) Protection - skin, portions of GI system (ex. esophagus w/abrasions from sharp foods)
2) Selective Barrier to facilitate or inhibit Exchange of substances -skin, capillaries, lung alveoli, urinary bladder
3) Secretion (gi tract, glands)
4) Absorption (intestine - nutrients)
5) Sensory Reception - neuroepithelium of sensory organs, ex. eye, ear, olfactory, taste)
In general, an Epithelium May Be Viewed As A...(select from previous card)
...A SELECTIVE BARRIER capable of facilitating or inhibiting the passage of specific substances between its free surface and the udnerlying CT. Thus, any substance that enters or is discharged from the body will usually pass THROUGH the epithelial cells, not between them.
Extracellular elements between epithelium?
Epithelium is composed of one or more layers of tightly connected cells which have NO EXTRACELLULAR ELEMENTS BETWEEN THEM; arranged as SHEETS OF CELLS that cover surfaces
Any contact w/ adjacent cells?
Epithelium has SPECIALIZED CONTACT BETWEEN ADJACENT CELLS which hold them tightly together and which allow communication btw cells
Polarity of epithelium? Adhesiveness of what side of epithelium to what
-Is functionally and morphologically Polarized.
-Has one free, or apical (top), surface which faces an internal or external space and is Non-Adhesive
-The opposite, or basal surface, adjoins the underlying CT and is adherent to the basement membrane
Apical and Basal Domains, Lateral Domains formed by what
Functionally distinct plasma membrane proteins and lipids exist on the apical and basal surfaces, forming distince Apical and Basal Domains, which are separated by the Lateral Domain
How does epithelium receive its nutrients and how is epithelium renewed
It is AVASCULAR and gets its nutrients by diffusion from vascular elements (blood vessel/capillaries) present in the underlying CT.
It is renewed by the mitotic dividsion of Stem Cells in response to normal wear and tear or after injury since they are very active
Where is simple squamous found (3) and functions (2)
Found in:
1) Lining of the vascular system (Endothelium)
2) Lining of peritoneal, pleural, and pericardial cavities (Mesothelium)
3) Pulmonary Alveoli

1) Barrier Exchange
2) Lubrication
Where is simple cuboidal found (3) and functions (3)
Found in:
1) Proximal and Distal Convoluted Tubules of Kidney
2) Glandular Ducts - ducts in exocrine glands
3) Ovarian Surface (germinal epithelium)

1) Absorption
2) Secretion
3) Barrier
Where is simple columnar found (4) and functions (2)
Found in:
1) Stomach
2) Small Intestines
3) Large Intestines/Colon
4) Gall Bladder

1) Absorption
2) Secretion
Where is stratified squamous found (4) and functions (2)
Found in:
1) Vagina
2) Oral Cavity
3) Esophagus (Non-Keratinized)
4) Skin/Epidermis and Fingernails (and parts of oral cavity) are classified as Stratified Squamous, Keratinized Epithelium - keratin has dead cells, no nuclei, full of keratin

1) Barrier
2) Protection
Where is stratified cuboidal found (2) and functions (2)
Found in:
1) Sweat Gland Ducts
2) Large Ducts of Exocrine Glands

1) Barrier
2) Conduit - a layer through which things are being transported
Where is stratified columnar found 3) and functions (2)
Found in:
1) Male urethra
2) Conjunctiva (eye)
3) Largest excretory ducts of exocrine glands

1) Barrier
2) Conduit
Where is pseudostratified epithelium found (5) and functions (3) and its description
Found in:
1) Trachea
2) Bronchii
In these 2, its further described as Pseudostratified, Ciliated, Columnar Epithelium w/Goblet Cells ("Respiratory Epithelium)
3) Epididymis
4) Ductus Deferens
In these 2, its described as Pseudostratified, Columnar Epithelium w/ Sterocilia
5) Olfactory Epithelium
Described as a Neuroepithelium w/ long modified cilia

Has the appearance of being stratified, but all cells rest on the basement membrane, so it really is a SIMPLE epithelium.

1) Secretion
2) Absorption
3) Conduit
Where is transitional epithelium found (4) and functions (2) and description
A truly STRATIFIED epithelium. Has a pillowy appearnce on the surface layer which varies with the degree of distension of the structure being examined.

Found in:
1) Ureter
2) Urethra
3) Urinary Bladder
4) Renal Calyces

1) Barrier - so urine stays where it is
2) Distensible properties
Where are neuroepithelial cells found (4) and functions (1)
Found in:
1) Taste buds
2) Olfactory epithelium
3) Retina (rods and cones)
4) Inner ear (sensory hair lines)

1) Specialized Sensory Functions
Where is myoepithelial cells found (1) and functions (1) and description
Myoepthelial cells are branched, stellate cells containing actin filaments. They are CONTRACTILE and help to expel the contents of some exocrine glands, which is where they are found
What are glandular epithelium cells specialized to make?
Where is their product stored?
What triggers the release of this product?
Specialized to manufacture and secrete proteins, lipids or complexes of carbohydrates and proteins

Secretory product is usually stored in membrane-bound vesicles (Secretory Granules)

Release is mediated by hormones or neural signaling/chemical messengers
Two main types of glandular epithelia (glands) and their secretions and where its secreted
Endocrine glands – No ducts; secretory products (hormones) enter blood stream or affect nearby cells

Exocrine glands – secrete onto an epithelial surface, usually via tubular ducts (except in the case of Unicellular Glands)
Unicellular Glands - have what type of cells to secrete what, where are these cells found, function of the cells' secretion
-Have Goblet Cells that are specialized to synthesize and secrete Mucin, which upon hydration forms a lubricating solution called Mucus.
-The cells are scattered among the epithelial columnar cells of the intestine and the respiratory system.
-Their mucus secretions cover the apical surfaces of the adjacent epithelial cells to lubricate and protect the epithelium. Lymphocytes can also be found next to them, but do not confuse them for goblet cells
Multicellular Glands - when do they develop, what 2 portions do they have and what does each portion do
-Develop when epithelia invade the underlying CT
-Usually consist of a Secretory Portion that synthesizes the secretion
-The Duct Portion trasports the secretion to the surface.
Multicellular Glands - Classifications (4)
1) If the duct is unbranched, the gland is called Simple
2) If the duct is branched, the gland is called Compound
3) If the secretory portion is shaped like a tube, the gland is Tubular
4) If it is flasklike it is Alveolar (aka Acinar).

-various comos of duct and secretory shapes are found in body. thus, glands may be simple straight tubular, simple coiled tubular, simple alveolar, etc. compound tubuloalveolar glands can have BOTH tubular and alveolar secretory units.
Some, but not all, exocrine glands contain serious or mucous cells, or both.
What do serous cells synthesize and secrete, where are these cells found (2)
-Synthesize and secrete proteins from RER w/ numerous polyribosomes located near the base of cell and secretory granules accumulate at the apical surface.
-Serous cells are present in the exocrine pancreas and in salivary glands.
What do Mucus-Secreting cells synthesize and secrete and where are they found (3)
-Synthesize and secrete glycoproteins called Muscins.
-Mucous cells are present in salivary glands, the respiratory system and the GI tract. Have an irregularly shaped and basally-located nucleus.
3 Mechanisms (Secretions) for the release of secretory products
1)Merocrine Secretion
2) Apocrine Secretion
3) Holocrine Secretion
Merocrine Secretion - when does it occur in which gland(s) does this secretion occur?
-Occurs when the membrane of the secretory granule fuses with the cell membrane (Exocytosis); no loss of other cellular material
-Occurs IN MOST exocrine and endocrine glands
Apocrine Secretion - when does it occur, in what gland
-Occurs when the secretory product is discharged along with parts of the cytoplasm and plasma membrane
-Mammary gland uses it for lipid component of milk
Holocrine secretion - when does it occur, in what gland
-Occurs when the product of secretion is shed with the entire cell
-Sebaceous glands of the skin
Myoepithelial cells role in secretion
-Contain contractile elements (actin and myosin) within the cytoplasm of their processes and communicate via gap junctions to provide coordinated contraction that squeezes out the contents of secretory portion of the gland following nervous or hormonal stimulation
Apical Surface Specializations (3) and their functions
1) Cilia - motile, beat synchronously in a particular direction so as to propel materials upward. Surrounded by 9 pairs + 2 microtubules. They are anchored to basal bodies in the apical cytoplasm, Kartagener’s syndrome - disorder caused by a defect in the action of the tiny hairs (cilia) lining the respiratory tract.
2) Microvilli - Maximize apical surface area, non-motile, striated brush border, contain a core of microfilaments (actin) that provide rigidity, the microfilaments anchored to the plasma membrane extend into apical cytoplasm where they insert onto network of actin and myosin II filaments called the Terminal Web
3) Sterocilia - not cilia, is branched microvilli present only in the epididymus, vas deferens, and sensory (hair) cells of ear, flexible but non-motile, cytoplasmic bridges, increase apical surface area, resorption of fluids secreted by testis, integral part of sensory apparatus.
The lateral domains of epithelial cells are the sites of various functionally and morphologically distinct...
And what are the functions of these things (3)
...Intercellular Junctions which are
1) responsible for the ADHERENCE of adjoining cells
2) provide a BARRIER FOR THE DIFFUSION of substances between the cells
3) allow for COMMUNICATION between cells.
Descriptions of Intercellular Junctions (4)
1)Zonula Occludens
2) Zonula Adherens
3) Macula Adherens
4) Gap Junctions
Zonula Occludens - primary function, consists of?, occludins and claudins, proteins found here and what do they do (2), pathogenic agents
-Primarily a barrier device, also referred to as Tight Junction, keeps paracellular pathways closed
-Consists of narrow band that Completely Encircles the cell (zonula = belt)
-Outer leaflets of the plasma membranes of adjoined cells appear to converge and fuse at multiple sites via transmembrane junctional proteins (Occludins and Claudins)
-ZO-1, ZO-2, ZO-3 proteins bind the cytoplasmic portion of the junctional proteins and they bind occludins and claudins to the actin cytoskeleton.
-Pathogenic agents such a Cholera Toxin act on the ZO proteins ot cause junctional permeability
Zonula Adherens - primary function, proteins found here (3) and their function, transmembrane adhesion molecule found here and its function
-Is an Adhesive Device located beneath zonula occludens, also form a belt around each epithelial cell
-On the cytoplasmic side of the junction, a dense plaque is formed by the protein Catenin and actin-binding proteins (Alpha-Actinin and Vinculin) which bind to the Actin Filaments of the terminal web
-Intercellular space present that is filled w/ a transmembrane ahdesion molecule (E-Cadherin) that binds to Ca++, which is essential to matinain junctional integrity
Macula Adherens - primary function, what is found here, transmembrane adhesive glycoproteins (2),
-An Adhesive Device that is also referred to as a Desmosome, effectively link the cytoskeletons of neighboring cells
-On the cytoplasmic side of the plasma membrane is a dense Plaque consisting of specialized proteins in which Intermediate Filaments (tonofilaments) are anchored
-Intercellular space between 2 desmosomes is filled by transmembrane adhesive glycoproteins called Desmocollins and Desmogleins.
Hemidesmosomes - are what, located on what type of cells, anchor what, attach cell via what?
-Half desmosomes located on basal plasmalemma of epithelial cells that are subjected to a lot of abrasion (skin, cornea, esophagus, vagina)
-Anchor cytoplasmic intermediate filaments
-Attach the cell to the basement membrane via transmembrane proteins called INTEGRINS.
-However, MOST epithelial cells attach to the basement membrane by simpler structures called Focal Adhesions that anchor cytoskeletal Actin Filaments to the basement membrane
Junctional Complex
zonula occludens, zonula adherens, macula adherens are collectively called the junctional complex aka the Terminal Bar in the LM
Gap Junctions - primary function, occur where, gaps bridged by what unit, what is unit composed of, what causes closure of gap junctions, cell-to-cell communication via?
-are Non-Adhesive and allow for Communication between neighboring epithelial cells
-Can occur anywhere along the lateral membranes of epithelial cells.
-Gap is bridged at intervals by functional units called Connexons
-Each connexon is formed by a group of 6 individual Connexin Protein units in each of the apposed cell membranes.
-High intracellular Ca++ concentrations cause closure of gap junctions - mechanism unknown!
-cell-to-cell communication via hydrophilic pores
Lateral and Basal Surface Folds - what are they, what do they lead to, found where (5)
-Tortuous infoldings are interdigitations between the lateral membranes of adjoining epithelial cells are especially PROMINENT IN EPITHELIA THAT TRANSPORT FLUID RAPIDLY, ex. in the intestine, gallbladder and kidney.
-The lateral cell surface area is thus increased, allowing more area for active transport of sodium ions into intercellular space and for water to follow the osmotic gradient.
-Other fluid transporting epithelia such as the proximal and distal kidney tubules and the straited ducts of the salivary glands have infoldings along their basal surfaces.
Functions of BM (7)
1 Structural attachment of epithelium to underlying
connective tissue

2 Separates epithelium from connective tissue

3 Selective permeability barrier in some areas
(kidney glomerulus)

4 Development of epithelial polarity and cell shape

5 Can organize proteins within epithelial plasma membranes
to affect signal transduction

6 Regulation of proliferation & differentiation (growth factor

7 Migratory substrate for epithelial cells during development
and repair
2 components of BM
Basal Lamina and Reticular Lamina
Basal Lamina - secreted by what, contains what which is separated by what
-Secreted by epithelium
-Consists of an electron-dense band called the Lamina Densa, which is separated from the epithelium by an electron-lucent layer called the Lamina Lucida
-The lamina densa contains laminin, fibronectin, type IV collagen and heparin sulfate proteoglycans.
-Laminin and fibronectin are attached to cell membrane by integrins
Reticular Lamina - secreted by what, composed of what, basal lamina attached to it how
-secreted by underlying CT
-composed of Reticular Fibers, which are fibrils of Type III Collagen
-Anchoring Fibers that consist of Type VII Collagen attach the basal lamina to the reticular lamina