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STRUCTURES - WEEK 1 > LEC 6: Epithelial Cell Specialization - 08.19.2014 > Flashcards

LEC 6: Epithelial Cell Specialization - 08.19.2014 Flashcards

1
Q

Where are epithelial cell specializations found

A
  1. Intercellular surfaces (between cells)
  2. Luminal surfaces
  3. Basal surfaces
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2
Q

What epithelial cell specializations are found on/near intercellular surfaces and what is their purpose

A
  • occluding, adhering, and communicating junctions
  • permit epithelia to form a continuous, cohesive layer so that all cells can communicate
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3
Q

What epithelial cell specializations are found on luminal surfaces

A

cilia, microvilli, stereocilia

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4
Q

What epithelial cell specializations are found on basal surfaces

A

basement membrane and hemidesmosomes

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5
Q

Occluding (Tight) Junctions

A
  • seal intercellular spaces so that luminal contents can’t get between cells
  • located directly below luminal surface of simple columnar epithelium
  • e.g. intestinal lining
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6
Q

What proteins make up occluding (tight) junctions

A

Claudin and Occludin

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7
Q

zonula occludens

A
  • each tight junction forms a continuous circumferential band or zonule around cell
  • “occludens zone”
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8
Q

Adhering Junctions: 2 types

A
  • bind epithelial cells together
  • act as anchorage site for cytoskeleton of each cell
  • two types:
    • zonula adherens - below luminal surface, deep to zonula occludens
    • desmosomes - deep to zonula adherens, as well as widely scattered elsewhere in epithelial intercellular surfaces
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9
Q

zonula adherens

A
  • form strong bond between adjacent cells
  • transcellular network
  • located deep to zonula occludens
  • Purpose/location (protein):
    • transmembrane (cadherins)
    • cystoplasmic face (actin filaments)
    • attachment proteins (catenins, vinculin, alpha-actinin)
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10
Q

Desmosomes (macula adherens)

A
  • provide structural integrity
  • large number in stratified squamous
  • located deep to adhering junctions, scattered
  • Purpose/location (protein):​​
    • intercellular (desmocollins)
    • transmembrane (desmogleins)
    • plaque (desmoplakin, keratin)
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11
Q

macula

A

Latin, “spot”

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12
Q

Junctional Complex

A
  • combination of zonula occludens (ZO), zonula adherens (ZA), and desmosomes
  • divides plasma membrane of cell into apical and basolateral surfaces
  • desmosomes widely scattered in epithelial tissues
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13
Q

location of junctions beyond epithelial cells

A

adhering junctions (ZA, desmosomes) and communicating (gap) junctions are not exclusive to epithelia and are also present in cardiac, visceral muscle

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14
Q

What proteins are associated with tight junctions

A
  • occludin
  • claudin
  • cingulin
  • ZO proteins
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15
Q

What proteins are associated with adhering junctions (zonula adherens)

A
  • actin filaments
  • cadherins
  • vinculin
  • catenins
  • alpha-actinin
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16
Q

What proteins are associated with macula adherens (desomosomes)

A
  • intermediate filaments
    • tonofilaments
    • cytokeratins
  • desmoplakins
  • desmoscollins
  • desmogleins
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17
Q

What does this slide depict

A

Simple columnar epithelial cells and the junctional complex (terminal bar)

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18
Q

Terminal Bar

A

Zonula Occludens, Zonula Adherens, Macula Adherens (Desmosomes)

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19
Q

Gap Junctions

also called: Communicating Junctions, Nexus Junctions

A
  • communication between cells
  • numerous in embryonic tissues
  • located below junctional complex (ZO, ZA, macula adherens)
  • regulate: Ca++, pH, cAMP
  • Purpose/Location (protein):
    • composition (connexon-6)
    • transmembrane proteins (connexin, 24 genes known)
20
Q

What affects the permeability of gap junctions

A
  • pH
  • Calcium (will close if too high)
  • ion concentration
  • cAMP
  • selectively permeable to (<1500 MW):
    • positively charged ions
    • amino acids
    • sugar
    • vitamins
    • hormones
21
Q

What are the two (2) epithelial cell specializations at the basal surface

A
  1. hemidesmosomes
  2. basement membrane
22
Q

Hemidesmosomes

A
  • anchor cytoskeleton at base of the cell to the basement membrane
  • located at basal plasma membrane
  • Purpose/location (protein):
    • composition (integrins, laminin)
23
Q

Basement membrane

A
  • physical support
  • cell attachment
  • selective barrier
  • growth and differentiation
  • special functions:
    • ultrafiltration in kidney
    • blood-air barrier (lung)
    • tumor metastasis
24
Q

What color is the basement membrane in Azan stain

A

blue

25
Q

Composition of the basement membrane

A
  • Type IV collagen (Exclusive to BM)
  • Laminin (binds collagen to BM)
  • Proteoglycans
  • Entactin (binds laminin to Type IV collagen)
  • Fibronectin (binds integrins of plasma membrane, produced by fibroblasts of the connective tissue)
  • Type VII collagen (binds basal lamina to subjacent collagen)
26
Q

Basal Lamina

A
  • Type IV collagen (Exclusive to BM)
  • Laminin (binds collagen to BM)
  • Proteoglycans
  • Entactin (binds laminin to Type IV collagen)
  • Fibronectin (binds integrins of plasma membrane, produced by fibroblasts of the connective tissue)
  • Type VII collagen (binds basal lamina to subjacent collagen)

NB: actually 3 layers of basal lamina seen in electron micrograph, but all represents the 1 layers seen in light microscope

27
Q

Cilia

A
  • simple cuboidal and simple columnar cells
  • up to 300/cell at apical surface for movement
  • functions include cleaning airways, transporting ovum
28
Q

Label the parts of the cilia

A

A. Plasma membrane

B. Peripheral microtubule doublet (9 pairs)

C. Central microtubule pair

D. Basal body

E. Plasma membrane

F. Microtubule triplet (9 pairs)

29
Q

What protein makes up the microtubules found in cilia

A

Tubulin

30
Q

What protein makes up the thin filaments found in microvilli

A

Actin

31
Q

Differences between cilia and microvilli

A
  • microvilli MUCH shorter than cilia
  • microvilli does not have active motion (no ATP)
32
Q

What type of cells are these and what are their distinguishing characteristics (hint: trachea slide)

A
  • Pseudostratified ciliated columnar
  • purpose of cilia at apical surface is to move along mucus and entrapped particles
33
Q

What type of cells are these and what are their distinguishing characteristics (hint: oviduct slide)

A
  • ciliated columnar epithelial cells
  • cannot be pseudostratified ciliated columnar because this isn’t the trachea
34
Q

Microvilli

A
  • about 1mm (micrometer) in length
  • composed of 20-30 actin filaments
  • covering of microvilli is glycoprotein, glycocalyx
  • contract and elongate to prevent clogging, no ATPase
35
Q

Terminal Web

A
  • found at apical surface in cells with microvilli
  • actin filaments stabilized by spectrin
  • anchors terminal web to apical cell membrane
  • when contracted, terminal web causes decrease in diameter of apex of the cell
    • microvilli spread apart, aiding in absorption
36
Q

Striated border

A
  • also known as brush border
  • microvilli covered surface of simple cuboidal and simple columnar epithelium cells
  • brush border found mainly in
    • small intestine tract
    • kidney
  • appears as fuzzy line/fringe in light microscope (individual microvilli too small to be resolved with LM)
37
Q

What kind of cells are shown in this slide and what distinguishes them

A
  • Simple columnar epithelium
  • striated border (individual microvilli cannot be resolved with LM)
38
Q

What do the red arrows point to

A
  • Striated border
  • found in simple columnar cells (these) or simple cuboidal cells
39
Q

What do the red arrows point to

A
  • Striated border (microvilli)
  • Kidney tubule, so cells are simple cuboidal
  • move liquid
40
Q

Stereocilia

A
  • found in male reproductive tract – epididymus
  • composed of actin
  • incapable of active movement - moves sperm
  • much longer than cilia
  • believed to facilitate absorption
41
Q

What is shown in this slide

A
  • sperm in epididymis being passively moved by stereocilia
42
Q

epidermolysis bullosa

A
  • skin blisteres resulting from mutations in keratin 5 and 14 genes
43
Q

bullous pemphigoid

A

autoantibodies against hemidesmosomes (blisters)

44
Q

immotile cilia syndrome

A

defect in dynein arms that affect ability of cilia to move

45
Q

epithelial cell tumors

A

if normal mechanisms for regulating epithelial turnover fail, tumors can develop

46
Q

carcinomas

A

malignant tumors that arise from membranous epithelia

47
Q

adenocarcinomas

A

malignant tumors that arise from glandular epithelium

STRUCTURES - WEEK 1 (8 decks)

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