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Foundations Downing > Epithelium > Flashcards

Epithelium Flashcards

1
Q

Which of the following are used to classify epithelium? Cilia, Microvilli & keratin

A

Both the presence of Cilia and keratin are used to classify epithelium. Microvilli are not.

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2
Q

Pear-shaped binucleate cells are characteristic of what type of epithelium?

A

Transitional epithelium

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3
Q

Communication between epithelial cells is most likely to occur through what?

A

Gap junctions

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4
Q

A gland having a tubular secretory component and a branched excretory duct component would be called a:

A

Compound tubular gland

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5
Q

Attachment of epithelia to underlying basal laminae is enhanced by what?

A

hemidesmosomes

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6
Q

Ridges of membrane fusion revealed by freeze-fractured epithelial cells indicate the presence of what?

A

tight junctions

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7
Q

The type of epithelium most likely encountered at sites of trauma would be what?

A

stratified squamous

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8
Q

In stratified squamous epithelium, the most common type of intracellular junction is what?

A

Desmosome

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9
Q

What is the most efficient intracellular junction in terms of preventing diffusion of materials between cells?

A

Zonula occludens

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10
Q

In epithelial cells, the term tonofilament is synonymous with what?

A

intermediate fillaments

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11
Q

The cell junction that forms a belt or girdle of adhesion around epithelial cells whose adjacent membranes remain about 20nm apart is called what?

A

zonula adherens

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12
Q

Match the following families of adhesion molecules with their respective functions:
Integrins, Cadherins & Selectins.
Mediate blood cell and endothelial cell adhesion.
Mediate cell-cell interactions.
Mediate cell-matrix interactions.

A

Integrins mediate cell-matrix interactions.
Cadherins - Cell-Cell interactions.
Selectins - blood cell-endothelial cell adhesion

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13
Q

Characteristics of Integrins:

A

Mediate cell-matrix interactions
Found in hemidesmosomes
Transmembrane proteins
Occur as heterodimers with alpha, and beta subunits
3-4 divalent cations bound to one subunit
Frequently bind to RGD (arginine, glycine, aspartic acid) sequences found on extracellular matrix molecules (e.g., fibronectin)

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14
Q

Cadherin characteristics:

A
  • Homotypic, cell-cell adhesion molecules
  • **Calcium dependent
  • Found at adherens junctions: zonula adherens (belt desmosomes) and regular desmosomes between adjacent epithelial cells
  • Transmembrane proteins: two domains (extracellular and intracellular)
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15
Q

Cadherins bind w/ one another in cytosolic/extracellular side. On cytosolic/extracellular side, cadherins interact w/ proteins & actin filaments.

A

Extracellular; cytosolic

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16
Q

_______ are groups of cadherins acting as “spot welds”. On the cytosolic side, are plaques attached to microfilaments/intermediate filaments.

A

Desmosomes; intermediate filaments

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17
Q

What three attachment specializations make up junctional complexes?

A 
Tight junctions (zonula occludens)
Zonula adherens (belt desmosome)
Macula adherens (spot desmosomes)
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18
Q

Besides preventing leaking of lumen contents b/w cells, what other function do tight junctions (occludens) perform?

A

Occludens serve to create two domains: apical and a basolateral domain, each with distinct surface proteins.

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19
Q

Zonula adherens don’t have occludens; instead they have ______. What are they attached to?

A

Zonula adherens form a “belt” and have cadherens. They are attached to microfilaments/actin filaments.

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20
Q

From an epithelial cells apical side to its basement membrane side, what order do the attachment specializations go?

A

Top - zonula OCCLUDENS
Middle - zonula ADHERENS
Bottom - DESMOSOMES (macula adherens)

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21
Q

True or false, both zonula adherens and desmosomes have cadherens. Which uses actin? Which uses intermediate filaments?

A

True, both have cadherens that connect across extracellular space. Desmosomes’ cadherens are thicker together and noticable on an electron microscope. zonula adherens use actin/microfilaments. Desmosomes use intermediate filaments.

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22
Q

Nexus, or ______, form and connect adjacent cells permitting transmission of materials from cell to cell.

A

Gap junctions

23
Q

___ transmembrane protein subunits called ____ for a structure called a _____, which allows materials to pass from cell to cell in nexus (aka _____).

A

6 connexin subunits form the connexon structure which allows materials to pass from cell to cell in nexus/gap junctions.

24
Q

What are the two layers of the basement membrane called? Does the basement membrane test PAS+ or -?

A

basal lucinda and basal densa. The basement membrane tests PAS+

25
Q

Describe the basal lucinda makeup.

A
  • electron lucent portion of basement membrane
  • rich in glycoproteins laminin and entactin
  • laminin has specific domains that bind type IV collagen, heparan sulfate, and epithelial integrins
  • contains extracellular domain portions of epithelial cell membrane integrins
26
Q

Describe the makeup of the basal densa.

A
  • meshwork of type IV collagen
  • type IV collagen sandwiched by the proteoglycan perlacan containing heparan sulfate side chains
  • tightly anchored to the reticular lamina by several factors, including fibronectin
27
Q

Pemphigus vulgaris is an autoimmune disease that creates antibodies that attack what?

A

desmosomal proteins leading to surface blistering.

28
Q

Bullous pemphigoid is an autoimmune disease that creates antibodies that attack what?

A

hemidesmisome proteins leading to blisters in the lamina lucinda (dermal-epidermal junction) that, upon filling, bubble up.

29
Q

True or false, basal lamina stain red w/ Schiff’s test. Why?

A

True, because of aldehyde groups

30
Q

What forms the interface between basal lamina and underlying connective tissue?

A

lamina reticularis.

31
Q

Describe attributes of lamina reticularis.

A
  • type I and type III collagen
  • forms the interface between basal lamina and underlying connective tissue
  • basic groups of collagen bond with acidic groups of glycosaminoglycans (heparan sulfate) of lamina densa
  • fibronectin has both glycosaminoglycan-binding domains as well as collagen binding domains
32
Q

Microvilli surfaces:

A

have a very thick glycocalyx (PAS +) comprised of glycosaminoglycans

33
Q

Microvilli interior:

A

core of microfilaments

(a) run from terminal web to tip of microvillus
(b) contain actin

34
Q

Microvilli functions:

A

Increased surface area for absorption.

Secrete enzymes that simplify sugars

35
Q

stereocilia characteristics:

A

usually much longer than microvilli.
found in ducts of male reproductive system
Non-motile
increased surface of cells

36
Q

Cilia characteristics:

A

a. relatively long (5-10 mm) motile processes that extend from the apical surface of the cell
b. may occur singly or in large numbers
c. shaft covered with plasma membrane
d. ARISE from BASAL BODIES in the apical cytoplasm of the cells

37
Q

What is an axoneme?

A

Axoneme is the core of cilia with

  • two single microtubules that terminate where ciliary shaft joins basal body.
  • Nine peripheral pairs of fused double microtubules
    (a) each doublet joins a triplet of microtubules in the basal body
    (b) doublet structure
38
Q

Subfiber A in axoneme is complete/incomplete.

A

Subfiber A is complete; B is incomplete.

39
Q

What is dynein and what are nexin links? What function do they have in cilia motility?

A

Dynein arms are an ATP-splitting enzyme that
extend from subfiber A towards subfiber B of the adjacent tubule.
Nexin links each subfiber along the minus end.
Dynein trys to “walk” down the B fiber next to the A fiber it stems from. The two fibers can’t slide past each other because of the nexin links. Instead, cilia bend.

40
Q

_____ ____ is an example of primary ciliary diskynesia characterized by aberrant _____ in cilia and flagella. The symptoms are chronic respiratory conditions and infertility. What else is interesting about those plagued with this condition?

A

Kartagener’s syndrome. The dynein arms are aberrant so cilia are not motile. Also of interest is that people with this condition have their organs located opposite to normal.

41
Q

Describe Metachronal rythms in cilia.

A

sequential beat resulting in waves that sweep across epithelial surface

42
Q

Flagella characteristics

A

Same basic structure as cillium, but are much longer and their beat is more random and whip-like in motion

43
Q

True or false, epithelium is avascular. What are vascular papillae?

A

True, epithilial tissues are avascular. Vascular papillae are capillary loops that shorten diffusion distances.

44
Q

How are epithelial tissues innervated?

A

Terminal branches of sensory nerves may penetrate basal lamina to terminate among epithelial cells

45
Q

How does epithelial tissue repair itself?

A

Epithelial cells CONSTANTLY renew themselves

Also, cells in wound regions become ameboid and increase in mitotic rate

46
Q

_______ membranes line CLOSED body cavities

What type of epithelial cells are always at the surface of these membranes?

A

Serous (sheets).

Mesothelium (simple squamous)

47
Q

Where are mucus membranes found? What type of epithelial cells are found at the surface of these cells?

A

mucus membranes line cavities and canals which CONNECT with EXTERIOR
Surface epithelium is variable

48
Q

Epitheliod

A

not looking at epithelium, but looks like epithelium

49
Q

Metaplasia

A

A REVERSIBLE change from one distinctive type of cell to another in a single spot

50
Q

Neoplasia

A

abnormal change from one distinctive cell type to a tumor cell

51
Q

Hyperplasia

A

increase in total cellularity (# cells)

52
Q

Hypertrophy

A

increase in size of structure, often due to hyperplasia

53
Q

Anaplasia

A

de-differentiation to more primitive form. Often very malignant.

Foundations Downing (2 decks)

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