Epithelial Surface Specialization Flashcards
What are the two parts of the basement membrane?
The basal and reticular laminae
What collagen is mainly found in the basal lamina?
Type IV
What collagen is mainly found in the reticular lamina?
Type III
What collagen is associated with anchoring fibers?
Type VII
What color do reticular fibers stain with silver?
Black
What color do reticular fibers stain with PAS?
Magenta
What color do reticular fibers stain with H&E?
They do not stain with H&E
What are some apical epithelial specializations?
Microvilli, cilia with basal bodies, stereocilia, glycocalyx
What are some lateral (junctional) epithelial specializations?
Zonary junctions - zonula occludens (tight/occluding junctions), zonula adherens (zonary adhering junctions)
Macular junctions - macula adherens (desmosomes), macula communicans (communicating junctions, gap junctions, or nexus)
What are some basal epithelial specializations?
Basement membrane, hemidesmosomes, in/outfoldings
What do microvilli and cilia have in common?
They are both evaginations of the cell membrane
What is different about microvilli and cilia with regard to their cores?
Microvilli have actin filaments in their cores and cilia have microtubules in theirs (the microtubules are organized into ring structures of 9 doublets surrounding 1 doublet and the actin is not arranged like this in microvilli).
What is different about microvilli and cilia with regard to size and uniformity?
Cilia are much larger (width- and length-wise) than microvilli and microvilli will have a more uniform appearance
What are four components of the glycocalyx and what color will it stain with PAS? What also dies the same color with this stain?
Glyolipids, glycoproteins, proteoglycans, and cholesterol
Purple
Goblet cells
What are stereocilia?
They’re long modified microvilli
True or false: Stereocilia are ubiquitous.
False
Where are sterocilia found?
- Male reproductive tract (epithelium of epididymis and ductus deferens)
- Sensory hair cells of inner ear
What is the motor molecule of cilia?
Dynein
What is the microtubule subunit?
Tubulin
What structures are basal bodies found in? Where in this structure are the basal bodies and what is inside of the basal bodies
At the base of cilia
Microtubules are inside
Kartagener’s syndrome occurs in patients that are affected with which disease?
Primary ciliary dyskinesia
What is the major cause of Primary Ciliary Dyskinesia? What is one symptom?
It is caused by the complete or partial absences of dynein arms in consequently abnormal cilia and flagella.
Infertility is a common symptom as this affects sperm motility and the ability of the female reproductive tract to move eggs and sperm along it.
What are the zonary types of cell junctions?
Zonula occludens (ZO; tight occluding junction) Zonula adherens (ZA; adhering band/zonule)
What are the punctate types of cell junctions?
Macula adherens (MA; desmosome, adhering spot) Macula communicans (nexus, gap junction)
What is the order from the apical surface to the basal surface of junctional complexes?
ZO (zonula occludens), ZA (zonula adherens), MA (macula adherens) - MA is not always present
What are two integral membrane or transmembrane proteins involved in occluding junctions?
Claudins and occludin
What are some intracellular peripheral membrane proteins in occluding junctions?
ZO-1, ZO-2, ZO-3
cingulin
spectrin
What are important cytoskeletal proteins in occluding junctions?
Actin
What are the integral membrane proteins in zonula adherens (adhering junctions)?
Integral membrane proteins: E-cadherins (they bind Ca++)
Cytoskeleton proteins: Actin
True or false: There is no reticular lamina in the alveoli in the lungs and the renal glomeruli.
True
What is the terminal bar and what is another name for it?
It is a junctional structure, also called the junctional complex, that acts in different ways to hold certain epithelial cells together at the apical end of the lateral cell boundaries.
What makes up one terminal bar and what is unique about it?
A tight junction, or zonula occluden, an adhering junction, or zonula adheren, and a desmosome, or macula adheren and it has polarity, always going in the above order from apical to basal surface.
What are one main function of tight junctions (zonula occludens)?
- It acts as a selectively permeable barrier (seals intercellular space, regulates paracellular transport, facilitates and promotes transcellular transport)
What is another main function of tight junctions (zonula occludens)?
- It influences cell polarity (separates apical from basal domains and restricts movement within the cell membrane)
What are the main functions of the zonula adherens (adhering junctions)?
- Important belt-like cell-cell adhesion units
- Thought to mediate folding and other 3D shapes of epithelia via actin and myosin interactions
- Appear to be required for tight junction formation
What are the principal components of the macula adherens or desmosomes?
Integral membrane proteins: cadherins - desmocollins and desmogleins
Cytoskeletal proteins: keratin
What are the principal functions of macula adherens or desmosomes?
- Important punctate, spot-like, cell-cell adhesion units
- Membrane anchor for intermediate filaments of cytoskeleton
- Transmit tensile strength through epithelium
- Cell signaling
True or false: Desmogleins are a type of cadherin.
True
What is impetigo?
It is a blistering disease caused by a bacterial infection that releases toxins that attack specific desmoglein proteins of desmosomes.
What is pemphigus?
It is an autoimmune blistering disease in which desmoglein is attacked by antibodies.
What are the principal components of gap junctions?
Integral membrane proteins - connexons (Cx)
What are the principal functions of gap junctions?
- Important spot-like (punctate) cell-cell communication and resource-sharing units
- Approximation to syncytium (many cells coming together to form one massive cell)
Where do desmosomes bear the brunt of mechanical stress?
Epidermis and the heart
What are the principal components of hemidesmosomes?
Integral membrane proteins - integrin (bind to laminin in ECM) and type XVII collagen
Cytoskeleton proteins - keratin (intermediate filaments)
What are the principal functions of hemidesmosomes?
- Important spot-like (punctate) cell-matrix adhesion units
- Serve as basal membrane anchor for intermediate filaments of cytoskeleton
- Transmit tensile strength from epithelium to ECM
What function are basal infoldings associated with? What organelle are they consequently associated with? How do these organelles stain?
Function: Ion transport and associated water movement
Organelle: Mitochondria that provide energy for the numerous ion pumps - they stain darkly
Where are basal infoldings commonly found?
In the proximal and distal tubules of the kidney and the striated ducts of major salivary glands
What is the principal function of basal outfoldings?
Increasing surface area of the epithelial cells for better attachment to the underlying connective tissue
Where are basal outfoldings commonly found?
Certain epithelia of the skin, like SSKE
True or false: Zonula adherens provide resistance to mechanical stress.
True
