Ch. 5 (Part 2) Epithelial Tissue (E3) Flashcards
1
Q
These epithelial cellular structures consist of an accumulation of transmembrane channels in a tightly packed array.
A
What are communicating (gap) junctions?
2
Q
Communicating (gap) junctions are formed by 2 half-channels called these.
A
What are connexons?
3
Q
What is the purpose of gap junctions in epithelial cells?
A
To allow for the exchange of ions, regulatory molecules, and small metabolites between cells
4
Q
List the 3 structural features that characterize the basal domain.
A
1) Basement membrane
2) Cell-to-extracellular matrix junctions
3) Basal cell membrane infoldings
5
Q
The basement membrane is a dense layer of specialized extracellular matrix proteins that consists of a {…} lamina (visible in EM) and a {…} lamina.
A
1) Basal
2) Reticular
6
Q
The basement membrane exhibits a positive reaction for this stain in light microscopy.
A
What is periodic acid-Schiff (PAS)?
7
Q
The basal lamina consists of a scaffold of {…} polymers with an underlying type {…} collagen suprastructure that provides an interaction site for many {…} (CAMs).
A
1) Laminin
2) IV
3) Cell adhesion molecules
8
Q
The {…} lamina is attached to the underlying {…} lamina (type III collagen) via {…} fibrils (type VII collagen) and to elastic fibers via {…} microfibrils.
A
1) Basal
2) Reticular
3) Anchoring
4) Fibrillin
9
Q
This basal domain structure serves as an attachment site of epithelia to connective tissue, compartmentalizes connective tissue, filters substances that pass to and from the epithelium, provides a scaffold during tissue regeneration, and is involved in cell signaling.
A
What is the basement membrane?
10
Q
Focal adhesions are integrin-based, dynamic {…} junctions that anchor {…} filaments to the {…} membrane. Their fast {…} and {…} provide the molecular bases for cell migration.
A
1) Anchoring
2) Actin
3) Basement
4) Formation
5) Dismantling
11
Q
Hemidesmosomes are integrin-based, stable {…} junctions that anchor the {…} filaments to the {…} membrane via {…} plaques.
A
1) Anchoring
2) Intermediate
3) Basement
4) Intercellular
12
Q
This class of glands secretes its products directly onto a surface or through epithelial ducts that may modify their secretion (concentrating, removing, or adding substances).
A
What is an exocrine gland?
13
Q
Exocrine glands are classified as either {…} glands, which produce mucous secretions, or {…} glands, which produce protein-rich watery secretions.
A
1) Mucous
2) Serous
14
Q
This term is used to describe exocrine glands whose secretory product is released via exocytosis.
A
What is merocrine?
15
Q
This term is used to describe exocrine glands whose secretory product is released in vesicles containing a thin layer of cytoplasm.
A
What is apocrine?
16
Q
This term is used to describe exocrine glands whose secretory product is accompanied by cell debris from the dying secretory cell.
A
What is holocrine?
17
Q
This class of glands lacks a duct system and secretes its products (hormones) into the bloodstream to reach a specific receptor on distant target cells.
A
What is an endocrine gland?
18
Q
This is a process that epithelial cells undergo in which they lose their epithelial characteristics and acquire mesenchymal cell features.
A
What is an epithelial-mesenchymal transition (EMT)?
19
Q
This is the reverse process of the epithelial-mesenchymal transition (EMT).
A
What is mesenchymal-epithelial transition (MET)?
20
Q
Both epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) occur is these 4 biological phenomena. List them.
A
1) Embryonic development
2) Wound healing
3) Fibrosis
4) Malignant transformation of cancer cells
21
Q
Epithelial cells belong to this cell population category.
A
What is the continuously renewing cell population?
22
Q
The replacement epithelial cells are are produced by the {…} division of adult {…} cells residing in different sites, called {…}, in various epithelia.
A
1) Mitotic
2) Stem
3) Niches
23
Q
These are the only known cellular structures that permit the direct passage of signaling molecules from one cell to another.
A
What are communicating (gap) junctions?
24
Q
A gap junction consists of an accumulation of {…} channels or {…} in a tightly packed array.
A
1) Transmembrane
2) Pores
25
What is a key procedure used to study gap junctions?
Measurement of electric current flow between cells
26
Electrical conductance studies show that neighboring cells joined by gap junctions exhibit a low electrical resistance between them when current flow is high; therefore, gap junctions are also called {...} junctions.
Low-resistance
27
High-resolution imaging techniques such as cryo-electron microscopy have been used to examine the structure of gap junctions. These studies reveal groups of tightly packed {...}, each formed by two half-channels called {...} embedded in the facing membranes.
1) Channels
2) Connexons
28
Each connexon contains six symmetrical subunits of an integral membrane protein called {...} (Cx) that is paired with a similar structure from the adjacent membrane; thus, each channel consists of 12 subunits.
Connexin
29
Mutations in connexin genes are major pathogenic factors in several diseases. For instance, a mutation in this connexin gene is associate with congenital deafness.
What is Connexin-26 (Cx26)?
30
Other mutations affecting these connexon genes have been identified in individuals with inherited cataracts.
What are Cx46 & Cx50?
31
What is the function of lateral cell surface folds (i.e., plicae)?
To create interdigitating cytoplasmic processes of adjoining cells
32
The lateral surfaces of certain epithelial cells show a tortuous (i.e., convoluted or folded) boundary as a result of {...} or {...} along the border of each cell with its neighbor.
1) Infolding
2) Plicae
33
The {...} space distends because of the accumulating fluid moving across the epithelium, but the degree of distension is limited by junctional attachments in the apical and basal portions of the cell.
Intercellular
34
This characteristic feature of the basal domain is a specialized structure located next to the basal domain of epithelial cells and the underlying connective tissue stroma.
What is the basement membrane?
35
These key components of the basal domain anchors the cell to the extracellular matrix; they are represented by focal adhesions and hemidesmosomes.
What are cell-to-extracellular matrix junctions?
36
These key characteristics increase the cell surface area and facilitate morphologic interactions between adjacent cells and extracellular matrix proteins.
What are basal cell membrane infoldings?
37
In contrast to H&E, the {...} (PAS) staining technique (Fig. 5.27b) results in a {...} reaction at the site of the basement membrane.
1) Periodic acid-Schiff
2) Positive
38
Not only is the basement membrane PAS-positive, but it is also...
Silver-reactive
39
The structural attachment site for overlying epithelial cells and underlying connective tissue comprised of a discrete layer of electron-dense matrix material (making up the upper portion of the basement membrane) 40- to 60-nm thick between the epithelium and the adjacent connective tissue.
What is the basal lamina?
40
What is another term for the basal lamina?
Lamina densa
41
When observed at high resolution, the basal lamina exhibits a network of fine, 3- to 4-nm protein filaments composed of {...}, a type {...} collagen molecule, and various associated {...} and {...}.
1) Laminins
2) IV
3) Proteoglycans
4) Glycoproteins
42
Between the basal lamina and the cell is a relatively clear or electron-lucent area is a structure referred to as this.
What is the lamina lucida?
43
The area outlined by the lamina lucida contains extracellular portions of CAMs, mainly {...} and {...} receptors.
1) Fibronectin
2) Laminin
44
With the development of new EM preparation techniques, the lamina lucida appears to be an {...} of fixation.
Artifact
45
The basal lamina in nonepithelial cells is referred to as this.
What is the external lamina?
46
There are 3 types of cells exhibit an extracellular electron-dense material that resembles the basal lamina of epithelium and are both PAS-positive and silver-reactive. What are these cell types?
1) Muscle cells
2) Adipocytes
3) Peripheral nerve-supporting cells
47
Analyses of basal laminae derived from epithelia in many locations (kidney glomeruli, lung, cornea, lens of the eye) indicate that they consist of approximately 50 proteins that can be classified into four groups. What are these 4 protein groups?
1) Collagens
2) Laminins
3) Glycoproteins
4) Proteoglycans
48
Which type of collagen is a major component that comprises 50% of all basal lamina proteins?
Type IV collagen
49
What is the basic function of Type IV collagen as it pertains to the basal lamina?
Formation of the basal lamina scaffold
50
What does the presence of different Type IV collagen isoforms within the basal lamina provide?
Specificity to the basal lamina associated with different tissues
51
This is a nonfibrillar type of collagen found in the basal lamina that plays an important role in stabilizing the structure of the external lamina in skeletal and cardiac muscle cells.
What is Type XV collagen?
52
This is a nonfibrillar type of collagen that is mainly present in vascular and epithelial basal laminae and is believed to function in angiogenesis.
What is Type XVIII collagen?
53
This collagen type forms anchoring fibrils that link the basal lamina to the underlying reticular lamina.
What is Type VII collagen?
54
These are cross-shaped glycoprotein molecules (140-400 kDa) composed of 3 polypeptide chains. They are essential in initiating the assembly of the basal lamina.
What are laminins?
55
Laminins possess binding sites for different {...} receptors in the basal domain of the overlying epithelial cells. They are involved in many {...} interactions.
1) Integrin
2) Cell-to-extracellular matrix
56
This small, rod-like sulfated glycoprotein (150 kDa) serves as a link between laminin and the type IV collagen network in almost all basal laminae.
What is entactin/nidogen?
57
Between collagens, laminins, glycoproteins, and proteoglycans, which molecule is mostly likely attributable to half of the basal lamina's volume?
Proteoglycans
58
What are the 2 key components of a proteoglycan?
1) Protein core
2) Sulfate side chain attached to the core (e.g., heparan, chondroitin, or dermatan)
59
Why are proteoglycans so negatively charged?
To help in regulating the passage of ions across the basal lamina
60
This is the most common heparan sulfate proteoglycan found in all basal laminae. It has a molecular weight of 400 kDa.
What is perlecan?
61
This 500 kDa proteoglycan is another important molecule found almost exclusively in the glomerular basement membrane of the kidney. It plays a major role in renal filtration as well as in cell-to-extracellular matrix interactions.
What is agrin?
62
What are the 3 domains that make up a single polypeptide chain in Type IV collagen?
NOTE: This isn't a trick question. These are the 3 components that make up every amino acid.
1) Amino-terminus domain (7S domain)
2) Collagenous helical domain
3) Carboxy-terminus globular non-collagenous domain (NC1 domain)
63
The six known chains of type IV collagen molecules (α1–α6) form three sets of triple helical molecules known as these.
What are collagen protomers?
64
What does the molecular structure of Type IV collagen determine?
The molecular structure determines Type IV collagen's role in the formation of the basal lamina network supra-structure
65
What event initiates basal lamina self-assembly?
NOTE: 2 molecular components are required to interact for self-assembly
The interaction of laminins & the Type IV collagen supra-structure coming together to form a sheet-like structure
66
Studies using cell lines have shown that the first step in the self-assembly of the basal lamina is {...} polymerization of laminin molecules on the basal cell surface domain.
Calcium-dependent
67
What are the 2 main structures that make up the basement membrane?
1) Basal lamina
2) Reticular lamina
68
What type of collagen makes up the reticular lamina?
Type III
69
These fibrils are usually found in close association with hemidesmosomes and are 1 of 3 connective tissue mechanisms mentioned in the text that help attach the basal lamina to the underlying connective tissue.
What are anchoring fibrils?
70
What type of collagen makes up anchoring fibrils?
Type VII
71
Anchoring fibrils can either loop back to the basal lamina OR extend to these structures found in the connective tissue matrix.
What are anchoring plaques?
72
The anchoring fibrils entrap type {...} collagen (reticular) fibers in the underlying connective tissue, which ensures sound epithelial anchorage.
III
73
This is an inherited blistering skin disease in which the epithelium is detached below the basement membrane.
What is dystrophic epidermolysis bullosa?
74
Mutations in this collagen gene will result in dystrophic epidermolysis.
What is the collagen VII gene?
75
Since mutations in the collagen VII gene can result in dystrophic epidermolysis bullosa, what can be said about the importance of anchoring fibrils as they relate to anchoring junctions?
Anchoring fibrils are critical to the function of the anchoring junctions
76
These structures are 10–12 nm in diameter and attach the lamina densa to elastic fibers. They are another connective tissue mechanism that allow the attachment of the basal lamina to the underlying connective tissue.
What are fibrillin microfibrils?
77
What main disorder can a mutation in the fibrilllin gene (FBN1) cause?
Marfan syndrome
78
These projections interact directly with the reticular lamina to form an additional binding site with type III collagen.
What are the discrete projections of the lamina densa?
79
List the 3 structures/mechanisms, on the connective tissue side, that help attach the basal lamina to the underlying connective tissue.
1) Anchoring fibrils
2) Fibrillin microfibrils
3) Discrete projections of the lamina densa
80
List the 5 main functions of the basal lamina.
1) Structural attachment
2) Compartmentalization
3) Filtration
4) Tissue scaffolding
5) Regulation & cell signaling
81
In what 2 ways is the tissue scaffolding function of the basal lamina beneficial to us?
1) Regeneration/healing
2) Acting as a protective barrier against tumor cell invasion
82
These junctions maintain the morphologic integrity of the epithelium-connective tissue interface.
What are anchoring junctions?
83
List the 2 main types of anchoring junctions.
1) Focal adhesions
2) Hemidesmosomes
84
This type of anchoring junction anchor the actin filaments of the cytoskeleton into the basal lamina.
What are focal adhesions?
85
These anchoring junctions anchor the intermediate filaments of the cytoskeleton into the basement membrane.
What are hemidesmosomes?
86
What do focal adhesions do for the actin cytoskeleton and the extracellular matrix proteins?
Focal adhesions form a structural link between the cytoskeleton & ECM proteins
87
Give an example of the prominent role that focal adhesions play during dynamic changes in epithelial cells.
Migration of epithelial cells in wound repair
88
Coordinated remodeling of the actin cytoskeleton and the controlled formation and dismantling of focal adhesions provide the {...} bases for cell migration.
Molecular
89
What is the main transmembrane protein family found in a focal adhesion?
Integrins
90
What 2 types of proteins do integrins interact with while on the cytoplasmic face of the cell membrane?
1) Actin-binding proteins
2) Regulatory proteins
91
Name 2 regulatory kinase proteins found in focal adhesions.
1) Focal adhesion kinase
2) Tyrosine kinase
92
Focal adhesions are also important sites for signal {...} and {...}. This phenomenon, known as {...}, allows cells to alter their adhesion-mediated functions in response to external mechanical stimuli.
1) Detection
2) Transduction
3) Mechanosensitivity
93
Which cell surface (apical/lateral/basal) are hemidesmosomes found on? What purpose do they serve on this surface?
Basal surface; they provide increased adhesion to the basal lamina
94
When observed with the EM, the hemidesmosome exhibits this plaque on the cytoplasmic side of the basal plasma membrane.
What is the intracellular attachment plaque?
95
What protein family is predominantly found in the intracellular attachment plaque?
Desmoplakin-like family of proteins
96
These are the majority of transmembrane proteins found in the hemidesmosome.
What is the integrin class of cell matrix receptors?
97
What is the purpose of the infoldings at the basal cell surface?
To increase the surface area of the basal cell domain for a greater number of available transport proteins & channels
98
This is a secretory activity in which some epithelial cells secrete substances that do not reach the bloodstream but rather affect nearby cells.
What is paracrine signaling?
99
This is a type of secretory activity/messaging in which an epithelial cell may secrete molecules that bind to receptors that are present on the same cell.
What is autocrine signaling?
100
Apocrine secretion is a mechanism mostly found in this type of gland.
What is the lactating mammary gland?
101
In holocrine secretion, the secretory product accumulates within the maturing cell, which simultaneously undergoes destruction orchestrated by {...} pathways.
Apoptotic (i.e., programmed cell death)
102
Holocrine secretion is a mechanism mostly found in 2 types of glands. List them.
1) Sebaceous glands (skin)
2) Tarsal glands (eyelid)
103
This class of exocrine glands is the simplest in structure. The secretory component consists of single cells distributed among other nonsecretory cells.
What are unicellular glands?
104
Give an example of a unicellular gland.
The mucus-secreting goblet cell
105
This class of exocrine gland is composed of more than one cell and exhibits varying degrees of complexity.
What are multicellular glands?
106
In multicellular glands, an unbranched duct is considered...
Simple
107
In multicellular glands, a branched duct is considered...
Compound
108
In a multicellular gland, if the secretory portion is tube-shaped, the gland is {...} in shape.
Tubular
109
In a multicellular gland, if the secretory portion is flask- or grape-shaped, the gland is {...} or {...}.
1) Alveolar
2) Acinar
110
In a multicellular gland, if the secretory tube ends in a sac-like dilation, the gland is {...}
Tubuloalveolar
111
What are the 3 types of tubular secretory portions in multicellular glands?
1) Straight
2) Branched
3) Coiled
112
What are the 2 types of alveolar secretory portions in multicellular glands?
1) Single
2) Branched
113
What is the difference between mucous and serous secretions?
Mucous - viscous, slimy
Serous - watery
114
What do serous cells produce in contrast to mucus-secreting cells?
Poorly or non-glycosylated protein secretions
115
These are clusters of cells found in the parotid gland and pancreas.
What are serous cell-containing acini?
116
In routine tissue preparation, the serous cells are more removed from the lumen of the acinus and are shaped as crescents or {...} (half-moons) at the periphery of the mucous acinus.
Demi-lunes
117
What 2 processes does the epithelial-mesenchymal transition (EMT) make cells more resistant to?
Apoptosis & anoikis (cell detachment-induced apoptosis)
118
The reprogramming and conversion of epithelial cells into a mesenchymal phenotype during EMT is initiated by an alteration in the balance of the concentration of these proteins.
What are local cytokines?
119
Local cytokine concentrations upregulate specific transcription factors called these.
What are EMT-TFs?
120
When do Type 1 EMT/MET processes occur?
Embryonic development
121
When do Type 2 EMT/MET processes occur?
Wound healing (i.e., reparative fibrosis)
122
In pathological conditions, Type 2 EMT/MET processes can lead to the abnormal formation of connective tissue causes excessive deposition of fibers in the extracellular matrix. What is this type of fibrosis called?
Progressive fibrosis
123
When does the Type 3 EMT process occur?
During the malignant process
124
In Type 3 EMT (e.g., malignant process), transformed cancer cells can invade tissues and migrate to these sites via lymphatic or blood vessels.
What are distal metastatic sites?
125
What is the average rate of cell turnover in the stratified squamous epithelium of the skin?
NOTE: days long process
47 days
126
Which layer of the epidermis undergoes mitosis for continuous cell renewal?
Stratum basale
127
The discovery and generation of these cells demonstrates that somatic adult cells can be reprogrammed to a pluripotent state by the enforced expression of several embryonic transcription factors.
What are induced pluripotent stem (iPS) cells?
128
These epithelial cell populations have very little mitotic activity.
What are stable cell populations?
129
Give an example of an organ with stable cell populations.
The liver
130
Although hepatocytes (liver cells) are considered a stable cell population, how does the liver heal?
Active proliferation of undamaged hepatocytes as a response to significant trauma
