Ch. 5 (Part 2) Epithelial Tissue (E3) Flashcards
These epithelial cellular structures consist of an accumulation of transmembrane channels in a tightly packed array.
What are communicating (gap) junctions?
Communicating (gap) junctions are formed by 2 half-channels called these.
What are connexons?
What is the purpose of gap junctions in epithelial cells?
To allow for the exchange of ions, regulatory molecules, and small metabolites between cells
List the 3 structural features that characterize the basal domain.
1) Basement membrane
2) Cell-to-extracellular matrix junctions
3) Basal cell membrane infoldings
The basement membrane is a dense layer of specialized extracellular matrix proteins that consists of a {…} lamina (visible in EM) and a {…} lamina.
1) Basal
2) Reticular
The basement membrane exhibits a positive reaction for this stain in light microscopy.
What is periodic acid-Schiff (PAS)?
The basal lamina consists of a scaffold of {…} polymers with an underlying type {…} collagen suprastructure that provides an interaction site for many {…} (CAMs).
1) Laminin
2) IV
3) Cell adhesion molecules
The {…} lamina is attached to the underlying {…} lamina (type III collagen) via {…} fibrils (type VII collagen) and to elastic fibers via {…} microfibrils.
1) Basal
2) Reticular
3) Anchoring
4) Fibrillin
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.
What is the basement membrane?
Focal adhesions are integrin-based, dynamic {…} junctions that anchor {…} filaments to the {…} membrane. Their fast {…} and {…} provide the molecular bases for cell migration.
1) Anchoring
2) Actin
3) Basement
4) Formation
5) Dismantling
Hemidesmosomes are integrin-based, stable {…} junctions that anchor the {…} filaments to the {…} membrane via {…} plaques.
1) Anchoring
2) Intermediate
3) Basement
4) Intercellular
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).
What is an exocrine gland?
Exocrine glands are classified as either {…} glands, which produce mucous secretions, or {…} glands, which produce protein-rich watery secretions.
1) Mucous
2) Serous
This term is used to describe exocrine glands whose secretory product is released via exocytosis.
What is merocrine?
This term is used to describe exocrine glands whose secretory product is released in vesicles containing a thin layer of cytoplasm.
What is apocrine?
This term is used to describe exocrine glands whose secretory product is accompanied by cell debris from the dying secretory cell.
What is holocrine?
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.
What is an endocrine gland?
This is a process that epithelial cells undergo in which they lose their epithelial characteristics and acquire mesenchymal cell features.
What is an epithelial-mesenchymal transition (EMT)?
This is the reverse process of the epithelial-mesenchymal transition (EMT).
What is mesenchymal-epithelial transition (MET)?
Both epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) occur is these 4 biological phenomena. List them.
1) Embryonic development
2) Wound healing
3) Fibrosis
4) Malignant transformation of cancer cells
Epithelial cells belong to this cell population category.
What is the continuously renewing cell population?
The replacement epithelial cells are are produced by the {…} division of adult {…} cells residing in different sites, called {…}, in various epithelia.
1) Mitotic
2) Stem
3) Niches
These are the only known cellular structures that permit the direct passage of signaling molecules from one cell to another.
What are communicating (gap) junctions?
A gap junction consists of an accumulation of {…} channels or {…} in a tightly packed array.
1) Transmembrane
2) Pores
What is a key procedure used to study gap junctions?
Measurement of electric current flow between cells
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
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
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
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)?
Other mutations affecting these connexon genes have been identified in individuals with inherited cataracts.
What are Cx46 & Cx50?
What is the function of lateral cell surface folds (i.e., plicae)?
To create interdigitating cytoplasmic processes of adjoining cells
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
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
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?
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?
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?
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
Not only is the basement membrane PAS-positive, but it is also…
Silver-reactive
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?
What is another term for the basal lamina?
Lamina densa
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
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?
The area outlined by the lamina lucida contains extracellular portions of CAMs, mainly {…} and {…} receptors.
1) Fibronectin
2) Laminin
With the development of new EM preparation techniques, the lamina lucida appears to be an {…} of fixation.
Artifact
The basal lamina in nonepithelial cells is referred to as this.
What is the external lamina?
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
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
Which type of collagen is a major component that comprises 50% of all basal lamina proteins?
Type IV collagen
What is the basic function of Type IV collagen as it pertains to the basal lamina?
Formation of the basal lamina scaffold
What does the presence of different Type IV collagen isoforms within the basal lamina provide?
Specificity to the basal lamina associated with different tissues
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?
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?
This collagen type forms anchoring fibrils that link the basal lamina to the underlying reticular lamina.
What is Type VII collagen?
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?
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
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?
Between collagens, laminins, glycoproteins, and proteoglycans, which molecule is mostly likely attributable to half of the basal lamina’s volume?
Proteoglycans
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)
Why are proteoglycans so negatively charged?
To help in regulating the passage of ions across the basal lamina
