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BIO230 Final > Week 8 > Flashcards

Week 8 Flashcards

1
Q

What is epithelial tissue?

A

cells directly connected to each other with minimal extracellular matrix

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2
Q

What is the purpose of epithelial tissue?

A

mechanical stresses are transmitted from cell to cell by cytoskeletal filaments anchored to cell=matrix and cell-cell adhesion sites

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3
Q

What is connective tissue?

A

cells dispersed through the extracellular matrix

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4
Q

What is the purpose of connective tissue?

A

extracellular matrix directly bars mechanical stresses of tension and compression

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5
Q

Where are epithelial cells found?

A

line surfaces, cavities, and organs

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6
Q

What is an example of epithelial cells on the skin?

A

protective epithelial cell layers on the surface of the organism

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7
Q

What is an example of epithelial cells in the digestive tract?

A

absorptive epithelial cells lining a cavity of the organism

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8
Q

How are epithelial cells polarized?

A
  • each cell surface must be different to perform different functions
  • these cell surfaces define the inside vs outside of the organism or tissue
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9
Q

What is the basic structure of an epithelial cell?

A
  • apical side
  • tight junction
  • cell-cell anchoring junctions
  • channel-forming junction
  • cell-matrix anchoring junctions
  • basal side
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10
Q

What is the function of tight junctions in epithelial cells?

A

seal gaps between epithelial cells

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11
Q

What is the function of adherens junctions in epithelial cells?

A
  • a type of cell-cell anchoring junction
  • connects actin filament bundle in one cell with that in the next (forms adhesion belts)
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12
Q

What is the function of desmosomes in epithelial cells?

A
  • a type of cell-cell anchoring junction
  • connects intermediate filaments in one cell to those in the next
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13
Q

What is the function of gap junctions in epithelial cells?

A
  • a channel-forming junction
  • allows the passage of small water-soluble molecules from cell to cell
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14
Q

What is the function of hemidesmosomes in epithelial cells?

A
  • a type of cell-matrix anchoring junction
  • anchors intermediate filaments in the cell to the extracellular matrix
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15
Q

What is the function of actin-linked cell-matrix junctions in epithelial cells?

A
  • a type of cell-matrix anchoring junction
  • anchors actin filaments in cell to extracellular matrix
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16
Q

What are junctional complexes?

A

structures that connect cells to each other and to the extracellular matrix

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17
Q

What proteins mediate cell-cell connections at adherens junctions?

A

Cadherins mediate cell-cell connections at adherens junctions

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18
Q

How do integrins function in cell-matrix junctions?

A

heterodimeric proteins that bind to extracellular matrix proteins and anchor actin filaments

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19
Q

What is the role of cadherins in junctional complexes?

A

transmembrane proteins that are expressed by forming homophilic interactions, connecting adjacent cells, and linking to the actin cytoskeleton

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20
Q

What is required for cadherin interactions?

A

require the presence of Ca²⁺ ions

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21
Q

How do cadherins contribute to cell sorting?

A

sort into groups based on the specific types of cadherins they express (e.g., E-cadherins and N-cadherins), as different cadherins do not interact with each other

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22
Q

What does calcium do for cadherins?

A

rigidify the cadherin extracellular domains allowing them to connect with another cadherin domain

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23
Q

How can cells be sorted into groups based on homophilic cadherin interactions?

A

cells expressing different cadherins sort into two separate groups that do not interact

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24
Q

What role do cadherins play in morphogenesis?

A

form adhesion belts that can mediate morphogenesis by contracting and pulling cells together to form a tube

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25
Q

How do cadherins interact with actin filaments?

A
  • indirectly through adaptor protein
  • linking the actin cytoskeleton between adjacent cells in epithelial tissues
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26
Q

What role do different cadherins play in adhesion belts?

A

cells express different cadherins to establish new interactions and ensure neural tube closer

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27
Q

What happens in cadherin mutations during Drosophila embryogenesis?

A

can disrupt cell adhesion, leading to disorganized movement of cells and improper formation of tissues

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28
Q

How do tight junctions define the domains of the cell?

A

Apical domain: faces the surface, cavity, or organ
Basal domain: faces the inside of the body (basal and lateral domains are grouped into the basolateral domain)

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29
Q

What role do occludins and claudins play in tight junctions?

A

form homophilic interactions with their extracellular domains to directly link adjacent cells
- many rows form one functional tight junction

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30
Q

How do tight junctions affect glucose transport in epithelial cells?

A

prevent direct diffusion of substances like glucose from the gut lumen into connective tissue

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31
Q

What types of transporters are involved in glucose transport across the epithelial cell membrane?

A

Active transporters (apical domain) and passive (basolateral domain)

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32
Q

What is the role of active transporters?

A

move glucose into the epithelial cell on the apical domain
- Na+ driven glucose transporter brings glucose into the cell from low con. to a high conc.

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33
Q

What is the role of passive carriers?

A

allows glucose to diffuse out of the epithelial cell into the connective tissue/blood
- passive glucose transporter brings out of the cell from a high conc. to a low conc.

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34
Q

What role do cell-matrix junctions play in epithelial and connective tissue?

A

epithelial: adhesion to the basal lamina extracellular matrix
connective: cell interaction with the extracellular matrix and cell movement

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35
Q

How can polarity cues establish cell cohesion?

A

Adherens junctions form first and provide polarity cues that define the apical and basolateral domains

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36
Q

What are the polarity cues for making the apical side?

A

PAR and Crumbs

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37
Q

What is the polarity cue used to make the basolateral domain?

A

Scribble

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38
Q

What is a primary landmark in multicellular development?

A

an initial signal or structure that establishes a basis for further development and organization within a multicellular organism

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39
Q

How can an initial landmark influence subsequent development?

A
  • by providing cues for cell behavior, such as polarity, differentiation, and organization
  • For example, the entry of a sperm can create an initial polarity signal in the fertilized egg
  • Or the receptor activity of neutrophils, which creates polarity in the cell
40
Q

How does an initial landmark lead to cell polarization?

A

can create the asymmetrical distribution of internal polarity cues during cell division

41
Q

What are the key components of cell polarity that define a functional epithelium?

A
  • intracellular trafficking
  • cytoskeleton organization
  • cell cohesion
  • a functional epithelium defines organs and organisms
42
Q

What can changes to cell interactions lead to?

A

cancer

43
Q

How do multicellular organisms develop?

A
  • tissue morphogenesis
  • tissue patterning
  • tissue renewal and stem cells
44
Q

What are the key concepts in multicellular development?

A
  • cell proliferation
  • cell differentiation
  • cell morphogenesis
45
Q

What is cell proliferation?

A

increase in cell numbers via cell division

46
Q

What is cell differentiation?

A

change in cell fate via cell signaling and differential genome expression

47
Q

What is cell morphogenesis?

A

change in cell shape, interactions and/or location

48
Q

What model organisms are used to study multicellular development?

A
  • C. elegans (worms)
  • Arabidopsis (plant)
  • drosophila
  • zebrafish
  • humans
  • mice
49
Q

How is multicellular development an ongoing process?

A

it occurs in adults from stem cells

50
Q

How can new developmental processes be initiated in adults?

A

an example is pregnancy

51
Q

What does the epidermis consist of?

A
  • squame about to flake off from the surface
  • several other skin cells
  • basal-cell layer (stem cells, which eventually become other skin)
  • basal lamina
52
Q

What does the dermis consist of?

A

connective tissue

53
Q

What is embryogenesis?

A

the process of development from a fertilized egg (sperm + egg) to a multicellular organism, just before birth

54
Q

What are the three key processes involved in multicellular development during embryogenesis?

A
  • cell proliferation (cleavage)
  • cell differentiation and morphogenesis (gastrulation)
55
Q

What are the basic steps involved in morphogenesis?

A

Generation of shape
1. cell internalization
2. elongation
3. fine repositioning of cells

56
Q

What are the basic mechanisms within cell internalization?

A
  • ingression/delamination
  • invagination/involution
57
Q

What are the tissue layers formed in morphogenesis during gastrulation?

A
  • ectoderm: epidermis and nervous system (on the surface)
  • mesoderm: muscles, connective tissue, bones, blood, kidneys, etc.
  • endoderm: guts, lungs, pancreas, liver, etc (moves inward to form future anus)
58
Q

What is gastrulation?

A

stage during morphogenesis where a change takes place from a ball of cells to an embryo with a gut and 3 germ layers

59
Q

What is an example of ingression/delamination?

A

the formation of the mesoderm during embryonic development

60
Q

What is ingression in the context of embryonic development?

A

the process where individual cells detach from the outer cell layer and migrate inward, undergoing an epithelial-to-mesenchymal transition.

61
Q

What is delamination in the context of embryonic development?

A

the process where a layer of cells splits or separates into two distinct layers, contributing to the formation of new tissue layers, such as the mesoderm

62
Q

Why is the epithelial-to-mesenchymal transition (EMT) significant in ingression?

A

allows epithelial cells to lose their cell-cell adhesion and gain migratory properties
- this is very rare in cells but this is an example where it normally happens

63
Q

What is the significance of carefully controlled epithelial-to-mesenchymal transition (EMT)?

A
  • essential for proper tissue organization and development
  • mutations or abnormalities can lead to developmental defects or diseases (cancer)
64
Q

What is an example of invangination/involution?

A

the formation of the endoderm during embryonic development

65
Q

What is invagination in embryonic development?

A

the process where attached cells in an epithelial cell sheet are pulled into the middle of the embryo while remaining attached, resulting in the formation of a pocket

66
Q

What is involution in embryonic development?

A

the process where cells curl in and grow to form the endoderm

67
Q

How does involution differ from invagination?

A

Invagination = the folding of a sheet of cells into the embryo (forms a pouch)
Involution = the curling in of cells to form a new layer while remaining attached

68
Q

What is the significance of the neural tube formation in relation to invagination/involution?

A

vertebrate neural tube forms via invagination/involution, where specific cells differentiate from the ectoderm to form the neural plate, which then invaginates to create the neural tube, instructions include differential gene expression (different cadherins)

69
Q

What are the main outcomes of invagination during embryonic development?

A

leads to the formation of key structures such as the gut tube

70
Q

What is convergent extension?

A

a morphogenetic process where cells converge (move closer together) and extend (elongate) in one direction
- results in elongation

71
Q

How does convergent extension contribute to elongation?

A

cells crawl together to form a narrower and longer shape, which increases the length of the tissue
- reduces its width

72
Q

What are the two main steps involved in convergent extension?

A
  1. Convergence: Cells move towards a central line or axis
  2. Extension: Cells elongate in the direction of the axis, resulting in tissue elongation
73
Q

What is mass cell migration?

A

the coordinated movement of groups of cells together, often to form different shapes or structures

74
Q

How does mass cell migration contribute to elongation?

A

cells can move individually or collectively to elongate a tissue or structure

75
Q

What are the two types of collective cell migration?

A

Chain-type migration: less adherent cells
Sheet-type migration: more adherent cells

76
Q

What asymmetric processes lead to elongation?

A
  • cell growth
  • cell division
  • matrix deposition
77
Q

How does asymmetric division contribute to directional cell growth?

A

result in cells growing in one direction

78
Q

What is the role of the plant cell wall in cell elongation?

A
  • made of polysaccharides like cellulose
  • constricts expansion, forcing growth in one direction, which leads to elongation.
79
Q

How does cellulose distribution affect plant cell growth?

A

The asymmetrical distribution of cellulose in the cell wall can direct the expansion of the cell

80
Q

What guides the deposition of the plant cell wall?

A

microtubules

81
Q

How does the organization of microtubules affect plant cell elongation?

A

facilitate directional elongation by ensuring that cellulose is deposited in a specific orientation, while disorganized microtubules can disrupt this process, leading to non-directional cell swelling

82
Q

What is fine repositioning of cells?

A

the process by which cells are moved to specific locations within a developing tissue or organism

83
Q

What are the mechanisms involved in fine repositioning of cells?

A
  1. Migration of whole cells.
  2. Migration of cell extensions (e.g., axon growth cones).
84
Q

How do whole cells migrate during development?

A

by moving in response to extracellular signals, which can guide their movement toward specific destinations (the development of the cerebral cortex)

85
Q

What role do attractants play in cell migration?

A

they are extracellular signals that direct the movement of cells or cell extensions in a particular direction (axon guidance)

86
Q

In the development of the cerebral cortex, where are the first-born neurons located?

A

deeper layer of the cortex
- oldest cells

87
Q

How does the position of neurons change as more neurons are born in the cerebral cortex?

A

Last-born neurons (younger) migrate to the outer layer, while first-born neurons remain in the deeper layers

88
Q

What role do radial glial cells play in the development of the cerebral cortex?

A

serve as a scaffold for migrating neurons to reach their final positions

89
Q

What is the significance of cell migration in the context of the cerebral cortex?

A

allows for the proper layering and organization of neurons

90
Q

What are the basic steps involved in cerebral cortex cell repositioning?

A
  • dividing of the progenitor cell
  • one cell stays put
  • other one travels up the radial glial cell
91
Q

What is the role of extracellular signals in axon positioning?

A

can polarize the migration of a cell extension, guiding the axon growth cone toward its target

92
Q

How do attractants influence axon growth?

A

Cells secrete axon-specific chemoattractants that guide the growth cone toward them

93
Q

What are the differences in signaling pathways between neutrophils and axon growth cones?

A

While the exact receptors, attractants, and signaling pathways differ, the underlying concepts of directional movement in response to signals are similar.

94
Q

What is the significance of the axon growth cone in neuronal development?

A

crucial for navigating and establishing connections to target cells

95
Q

What happens during the migration of axon growth cones?

A

migrate towards their targets by extending filopodia and lamellipodia, responding to guidance cues

96
Q

How do axons establish their final positions?

A

establish their final positions through a combination of directional growth, influenced by attractants and repulsive signals, as well as the migration of the growth cone

BIO230 Final (5 decks)

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