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Cytology > Lesson 5: Apical and basolateral specializations of epithelial cells > Flashcards

Lesson 5: Apical and basolateral specializations of epithelial cells Flashcards

1
Q

What are the two main types of epithelial tissues?

A

Lining epithelia and glandular/secreting epithelia.

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2
Q

What key feature distinguishes epithelial cells?

A

Polarity, with apical, lateral, and basal domains.

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3
Q

How do epithelial cells adhere to each other?

A

Through specialized junctions.

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4
Q

What role does epithelial tissue play in the body?

A

Acts as a barrier and mediates absorption, secretion, and transport.

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5
Q

What is morphological-functional polarity in epithelial cells?

A

The structural and biochemical differences between the apical and basal sides.

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6
Q

What is the role of the cytoskeleton in cell polarity?

A

Provides structural support and contributes to the function of the apical and basal specializations.

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7
Q

Name three types of apical specializations in epithelial cells.

A

Microvilli, cilia, and stereocilia.

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8
Q

What is the primary function of microvilli?

A

To increase the cell’s absorptive surface area.

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9
Q

What forms the structural basis of microvilli?

A

Actin microfilaments.

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10
Q

How do cilia differ structurally from microvilli?

A

Cilia are larger and contain microtubules in a 9+2 arrangement.

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11
Q

What is the function of motile cilia?

A

To move fluid or particles across the epithelial surface.

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12
Q

What are primary (monocilia) cilia, and what is their function?

A

Non-motile cilia functioning as sensory structures.

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13
Q

Where are stereocilia commonly found?

A

In the epididymis and inner ear.

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14
Q

What is the structural difference between stereocilia and cilia?

A

Stereocilia are made of actin filaments, not microtubules.

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15
Q

What are the three main types of lateral cell junctions?

A

Occluding, anchoring, and communicating junctions.

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16
Q

What is the function of tight junctions?

A

To prevent diffusion of water and substances between cells.

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17
Q

Which proteins are involved in tight junctions?

A

Claudins, occludins, and junctional adhesion molecules (JAMs).

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18
Q

What is the primary function of adherens junctions?

A

To connect the actin cytoskeletons of adjacent cells.

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19
Q

What transmembrane proteins are key in adherens junctions?

A

Cadherins and nectins.

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20
Q

What is the function of desmosomes?

A

To anchor intermediate filaments between cells, providing mechanical stability.

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21
Q

Which proteins are critical for desmosome function?

A

Desmocollin and desmoglein.

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22
Q

What is the role of gap junctions?

A

To allow direct communication between adjacent cells.

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23
Q

What structures form the channels in gap junctions?

A

Connexons.

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24
Q

What is the basement membrane?

A

A specialized structure linking epithelial cells to underlying connective tissue.

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25
Q

What are the two layers of the basement membrane?

A

Basal lamina and reticular lamina.

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26
Q

What composes the basal lamina?

A

Laminin, entactin, glycoproteins, and type IV collagen.

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27
Q

What is the function of hemidesmosomes?

A

To anchor epithelial cells to the basement membrane.

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28
Q

Which proteins mediate hemidesmosome adhesion?

A

Integrins and laminin.

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29
Q

How do basal infoldings aid in cell function?

A

They increase surface area for transport and are associated with mitochondria.

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30
Q

What is EMT?

A

Epithelial-to-Mesenchymal Transition: A process where epithelial cells acquire mesenchymal traits, enhancing mobility.

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31
Q

How does E-cadherin downregulation affect EMT?

A

It reduces cell adhesion, facilitating EMT.

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32
Q

What role does EMT play in cancer?

A

It contributes to carcinoma progression and metastasis.

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33
Q

What is the significance of tight junctions in disease?

A

Their dysfunction can lead to increased permeability and conditions like leaky gut.

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34
Q

What is pemphigus foliaceus, and how is it related to desmosomes?

A

An autoimmune disease caused by the loss of desmoglein 1, weakening cell adhesion.

35
Q

How do gap junctions contribute to cardiac function?

A

They facilitate electrical coupling between cardiomyocytes.

36
Q

Why is the basement membrane important in cancer metastasis?

A

It acts as a barrier; its disruption can enable cancer cell invasion.

37
Q

What is the glycocalyx, and where is it found?

A

A layer of glycoproteins and glycosaminoglycans covering microvilli, found on the apical surface of intestinal epithelial cells.

38
Q

How does the movement of cilia help in the respiratory system?

A

Cilia move mucus and trapped particles out of the airways, aiding in continuous cleaning.

39
Q

What structure is the basal body of a cilium derived from?

A

The centriole, which organizes microtubules.

40
Q

What is the primary structural component of stereocilia?

A

Actin microfilaments.

41
Q

What cytoplasmic proteins do occludins and claudins bind to in tight junctions?

A

ZO-1, ZO-2, and ZO-3 proteins.

42
Q

Which type of junction allows ions and small molecules to pass directly between cells?

A

Gap junctions.

43
Q

What are adherens junctions connected to within the cell?

A

The actin cytoskeleton.

44
Q

Why are desmosomes particularly abundant in the epidermis?

A

To provide mechanical strength in areas exposed to friction and abrasion.

45
Q

What protein family mediates the attachment of hemidesmosomes to the basement membrane?

A

Integrins.

46
Q

What layer of the basement membrane directly contacts the plasma membrane?

A

The lamina lucida.

47
Q

What type of collagen is predominantly found in the lamina densa?

A

Type IV collagen.

48
Q

How does the basement membrane regulate epithelial repair?

A

It acts as a scaffold for cell migration and proliferation during tissue regeneration.

49
Q

What staining technique highlights the basement membrane?

A

Periodic Acid-Schiff (PAS) staining.

50
Q

What biochemical changes occur in EMT?

A

Downregulation of E-cadherin and upregulation of mesenchymal markers like vimentin.

51
Q

How does EMT enhance the metastatic potential of cancer cells?

A

By increasing their migratory and invasive capabilities.

52
Q

What role does β-catenin play in EMT?

A

It translocates to the nucleus to activate gene transcription supporting mesenchymal traits.

53
Q

Which cell junction type is most affected during EMT?

A

Adherens junctions, due to E-cadherin downregulation.

54
Q

What environmental or genetic factors can trigger EMT?

A

Hypoxia, mutations, and transcriptional repression of epithelial markers.

55
Q

How are gap junctions visualized in research?

A

Using atomic force microscopy or fluorescent tagging.

56
Q

What condition arises from the loss of desmoglein in desmosomes?

A

Pemphigus foliaceus, an autoimmune blistering disease.

57
Q

How do hemidesmosomes contribute to tissue stability?

A

By anchoring epithelial cells firmly to connective tissue, crucial in the skin and oral cavity.

58
Q

Why is the basement membrane considered a selective barrier?

A

It controls the passage of cells and molecules, critical in preventing metastasis.

59
Q

How does EMT play a role in tissue development?

A

It is essential for processes like gastrulation and wound healing.

60
Q

What are the main protein components of the terminal web in microvilli?

A

Actin and filamin.

61
Q

How do tight junctions influence membrane protein distribution?

A

By preventing apical membrane proteins from diffusing into the lateral membrane.

62
Q

What happens to cilia in conditions like primary ciliary dyskinesia?

A

Their motility is impaired, leading to issues like chronic respiratory infections.

63
Q

What feature allows desmosomes to endure mechanical stress?

A

Their anchoring to intermediate filaments like keratin.

64
Q

In what tissues are stereocilia critical for function?

A

The epididymis (sperm maturation) and the inner ear (sensory function).

65
Q

What are the three domains of epithelial cell polarity?

A

Apical, lateral, and basal domains.

66
Q

How do cadherins mediate cell-cell adhesion?

A

By forming homophilic bonds and linking to actin filaments via catenins.

67
Q

What is the ultrastructure of cilia called?

A

The axoneme, featuring a 9+2 microtubule arrangement.

68
Q

How does the lamina lucida differ from the lamina densa?

A

The lamina lucida is clear and close to the plasma membrane, while the lamina densa is dense and contains type IV collagen.

69
Q

Why is cell polarity important in epithelial function?

A

It ensures directional processes like absorption, secretion, and barrier function.

70
Q

What cytoskeletal components contribute to epithelial cell polarity?

A

Microtubules, microfilaments (actin), and intermediate filaments (keratin).

71
Q

What type of intermediate filaments are present in epithelial cells?

A

Keratin filaments.

72
Q

How do microvilli contribute to epithelial function?

A

They increase the surface area for absorption, especially in intestinal cells.

73
Q

What is the terminal web, and how is it related to microvilli?

A

The terminal web is a dense network of actin filaments at the base of microvilli, providing structural support.

74
Q

What forms the striated or brush border of intestinal epithelial cells?

A

Microvilli together with the glycocalyx.

75
Q

What is the basal body, and what is its function in cilia?

A

The basal body is derived from the centriole and organizes the microtubules of cilia.

76
Q

What structural difference exists between motile cilia and primary cilia?

A

Primary cilia lack the central microtubules (9+0 arrangement) and do not have motor proteins.

77
Q

How do stereocilia differ from motile cilia?

A

Stereocilia are made of actin filaments and are non-motile, while motile cilia are made of microtubules.

78
Q

How long can stereocilia grow?

A

Up to 100 µm in length.

79
Q

What is the role of ZO proteins in tight junctions?

A

They link transmembrane proteins to the actin cytoskeleton.

80
Q

How do gap junctions contribute to the function of osteocytes in bone tissue?

A

They enable nutrient and signal exchange through long cytoplasmic projections.

81
Q

What components are found in the lamina lucida?

A

Laminin and integrins

82
Q

What is the function of the reticular lamina in the basement membrane?

A

It connects the basement membrane to underlying connective tissue.

83
Q

What are the main cellular changes during EMT?

A

Loss of cell polarity, reduced adhesion, and increased motility.

84
Q

How do tight junctions help maintain the blood-brain barrier?

A

By preventing the diffusion of harmful substances into the brain.

Cytology (5 decks)

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