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Epithelial specialization
USF COM co 2015 lecture 082911
13
Histology
09/11/2011

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Term
What's another name for occluding junctions and what are their characteristics?
Definition
Occluding junctions are also called cell-cell tight junctions. They seal neighboring cells and set up intercellular permeability barriers. They sit at the apical-lateral surface of a cell and are made up of adjacent layers of plasma membrane that are held together by occludins, claudins, and JAMs. Depending on the # of layers, the junction permeability can be altered. ZO1, ZO2, and ZO3 are tight junction proteins that link PM to cytoplasm (maybe by linking occludins, etc to cytoplasm). The tight junctions also associate with the actin cytoskeleton.
Term
Which type of cell-cell junction uses occludins, claudins, and JAMs.
Definition
Occluding or tight junctions.
Term
What type of junction uses ZO1, ZO2, and ZO3 and what is their purpose?
Definition
Occluding/tight junctions use these proteins to link PM to cytoplasm.
Term
Name three CAMs, (cell adhesion molecules), tell me which type of cell-cell junction uses them, and describe their purpose? What other proteins do these types of junctions use?
Definition
Cadherins, selectins, integrins, and IgGs interact with catenin and vinculin, which interact with actin in cytoskeleten in zona adherens of Adherens anchoring junctions. Also in adherens junctions, IFs attach to desmosomes and interact with desmoplakins and plakoglobins. Desmocollin and desmoglein pass through cell membranes. Seems like a lot, but look at similarities in names of proteins!
Term
What are hemidesmosomes and where are they found?
Definition
IF spot attachment points. As an example, desmoplakin-type proteins link integrins and type 17 collagen on cell membrane with type 4 collagen, laminin, and proteoglycans in basement membranes. Found on basal domain of epithelium
Term
Which types of junctions use connexons are what is their purpose?
Definition
Connexons are used in communicating junctions. They are made up of 6 subunits or combine w/ other proteins to form a channel.
Term
What types of specializations are found on the lateral domain of epithelium cells?
Definition
zona occludens, zona adherens, macula adherens, and gap junctions.
Term
Name three major components of the basement membrane
Definition
Collagen IV, laminins, perlecans (type of proteoglycan).
Term
What's another name for a desmosome and describe its characteristics?
Definition
Macula Adherens. Like a snap-button between cells. Has adhesion plaques beneath PM with tonofilaments that act as reinforcement roots.
Term
Which are closer to the apical surface of cells: tight junctions (zona occludens) or zona adherens?
Definition
Tight junctions/Zona occludens are closest to the apical surface of epithelial cells.
Term
What are two other names for gap junctions?
Definition
Nexus, macula communicans
Term
What is glycocalyx?
Definition
A complex carbohydrate/protein surface coat on apical surface of epithelium. Looks like peach fuzz. Has hydrolases and transport molecules.
Term
What are the three layers of the basement membrane/basal lamina?
Definition
1) lamina lucida - electron lucent layer just beneath epithelial cell. 2) lamina densa - dense amorphous layer. 3) lamina reticularis/fibroreticularis - contains collagen fibrils. (Not all tissues like the glomerulous have the lamina reticularis).