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69 Cards in this Set
- Front
- Back
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Tight junctions in epithelial cells help create two distinct domains?
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apical and basolateral
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What are the three important functions of intercellular junctions:
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1. cellular attatchment (adhering junctions)
2. sealing of the intercellular space (occluding junctions) 3. cell-cell communication (gap or communicating junctions) |
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Describe the polarization of epithelial cells.
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They have two structurally distinct regions of their plasma membranes, an apical cell surface and a basolateral cell surface.
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What type of tissue does epithelial tissue always sit on?
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Connective tissue
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Name some functions of the apical plasma membrane.
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regulation of nutrient and water uptake, regulated secretion pathway A, protection
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Name some functioins of the basal lateral membrane.
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signal reception and transduction, generation of ion gradients, constitutive pathway
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What makes up the basement membrane?
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Proteoglycans(perlecan-heparan sulfate), laminin, Type IV collagen
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The apical plasma membrane is enriched in _________ that help form a protective barrier from a low lumenal pH
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glycolipids
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Name a major component of the apical plasma membrane?
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Na+ dependent transporters
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Name a major component of the basal-lateral membrane?
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Na+/K+ ATPase
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Name some major components of the lateral plasma membrane.
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Tight junctions (ZO) block paracellular pathway, CAMs, ZA, Desomosomes, Gap junctions
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How is the basal layer attatched to the basement membrane (basal lamina)
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Through specific receptors for laminin, proteoglycans, and type IV collagen.
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fingerlike extensions found on the surface of many cells especially epithelial cells that require a large amount of surface area to function.
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Microvilli
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At the core of each microvillus is a rigid bundle of 10-50 parallel microfilaments called the ________ that extend from the tip of the microvillus down into the cell cortex.
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core filaments
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In microvilli, the most important actin bundling protein is ________. (0nly found in microvilli)
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villin
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These microvilli are short and uniform in length and usually found on intestinal epithelium.
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striated border microvilli
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These microvilli are long and less uniform and are found in the proximal tubules of the renal nephrons
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brush border microvilli
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Nonmotile microvilli found on the cells of the epididymal epithelium and hair cells of the inner ear.
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Stereocilia; NOT TRUE CILIA
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The actin filament bundle at the base of the microvilli is called what?
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rootlet filaments
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The rootlet filaments are anchored into a sepcialized region of the cortex called the
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terminal web; composed of a network of actin filaments, spectrin, and cytokeratin based intermediate filaments.
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The ____, which can bind both actin and intermediate filaments is thought to provide rigidity and stability to the cortex in this region.
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Spectrin
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All microvilli increase the cell surface area for secretion and absorption except for?
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stereocilia in the inner ear, they function as sensory receptors.
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Microplicae are found on the free surface of various cells and do what?
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increaes the surface area to play a role in holding and spreading mucus and other secretion products, and to maintain moisture on the free surface.
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In some multicellular glands, the surface area available for exocytosis is increased by slender ________________.
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intracellular secretory canaliculus.
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A unique example of an intracellular secretory canaliculus is?
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the parietal cells of the gastric mucosa
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invaginations of the basal plasma membrane with function of increasing the basal contact surface with the extracellular matrix
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basal infoldings; na/k pump
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The _______ is a system of basal infoldings ane cytoplasmic compartments betwen them. The compartments frequently contain _______ orientated perpendicularly to the basal lamina, giving a pattern of striations.
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basal labyrinth; mitochondria
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What enzyme is in high concentration in the basal infoldings?
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NA/K ATPase
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What are the four ways cells attatch to eachother?
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1. adhesive cementing substances
2. interdigitations 3. overlapping 4. intercellular junctions |
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________ are thought to confine the transport proteins (like the NA/glucose symport protein of the apical membrane) to their appropriate membrane domain by acting as diffusion barriers within the lipid bilayer of the plasma membrane.
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Tight junctions
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Adhering junctions are widely distributed among tissues subject to what?
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severe mechanical stress, like the heart, epidermis, and muscle.
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Adherens junctions and desmosomes hold cells together by using what protein family?
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cadherins
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Focal adhesions and hemidesmosomes hold cells together by using what protein family?
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integrins
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what are the three structural classifications of cell junctions?
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1.Zonula-girdle or belt-like region of the plasma membrane that surrounds each cell usually near the free surface.
2.Fascia-site of pathcy region of adjacent plasma membranes 3.Macula-site of spotlike region of adjacent pms. |
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What are the occluding junctions?
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Zonula occludens or tight juctions; fascia occludens
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What are the anchoring junctions?
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Zonula Adherens (adhesion belt), Fascia adherens, or macula adherens (desmosome) and hemidesmosome.
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What are the communicating juctions?
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Direct-gap juction
Indirect- signaling |
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Junction in which two interacting plasma membranes join dicretly to each other to occlude the intercellular space.
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Tight junction or ZO
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What is the major transmembrane potein in the tight junction?
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CLAUDIN; famiy of 16 transmembrane proteins forming linear fibrils in the occluding junctions. Creates the paracellular fusion barrier for solutes, ions, and water.
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A second major protein in tight junctions is the _______, which interact with four peripheral proteins, ZO-1,2,3 and AF-6. The ZO proteins anchor the strands to the actin cytoskeleton.
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occludin
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What are the functions of a tight junction?
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1. seal the EC space between adjacent epithelial cells thus preventing the flow of materials between epithelial cells in eather direction.
2. intramembrane barrier to the lateral diffusion and intermixing of apical and basolateral membrane components (also block diffusion of lipids in the outer but not inner leaflet) |
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Where is the fascia occlusens found?
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between capillary endothelial cells.
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beltlike junctin that encircles each of the interacting cells and is located near the apex of each cell just below the tight junction.
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ZA
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The ZA of one epithelial cell is directly adjcacent to the ZA in the next cell, and the interacting membranes are held together in a ___________ manner.
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calcium dependent
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The transmembrane protein that mediates the adhesion in a zonula adherens is __________.
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E-cadherin
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A contractile bundle of actin filaments lies adjacent to the ZA, the E-cadherins interact with these actin filaments via three intracellular attatchment proteins called ?
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the catenins.
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What makes up the terminal bar?
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ZO + ZA
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A network of interwoven actin filaments immediately beneath the free surface of some epithelial cells. These actin filaments attatch laterally to the ZA. This structure is known as the ?
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terminal Web
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This anchoring type junctin is found as part of the intercalated disc.
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Fascia adherens
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What is the main way cells are mechanically attatched to one another?
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macula adherens or desmosomes
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buttonlike points of intercellular contact that rivet cells together in a variety of tissues. Serve as anchoring sites for intermediate filaments.
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desmosomes or MA
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The type of intermediate filament attatched to desmosomes depends on the cell type _____ in epithelial cells or _______ in cardiac muscle cells.
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keratin filaments (tonofilaments); Desmin filaments
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On the cytoplasmic surface of each desmosome is a dense plaque composed of a mixture of intracellular proteins including (2).
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desmoplakins and plakoglobin.
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The transmembrane linker protein associated with desmosomes is
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the cadherins
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junction connecting the basal surface of epithelial cells to the underlying basal lamina
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hemidesmosome
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The transmembrane linker proteins in hemidesmosomes are the __________.
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integrins
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What makes up a junctional complex?
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ZO + ZA + desmosomes
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What two types of communicating junctions are there?
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direct and indirect
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What is the direct communicating junction called? and what is its structue?
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Gap Junction; 6 identical protein subunits form a hydrophilic pre with a 1.5NM DIAMETER, this unit is called a C0NNEXON.
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Gap junctions are said to couple what between cells?
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They couple the cells electrically and metabolically, coordinating the activities and responses of the cells within a tissue.
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What are the four types of indicrect singaling?
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1.autocrine
2.paracrine 3.endocrine 4.synaptic |
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a cell secretes sgnal molecules that can bind back on itsown receptors ex. growth factors such as prostaglandins and interleukins.
Type of signaling? |
autocrine
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cells secrete local chemical mediators which ar so rapidly taken up, destroyed or immoblilized that the mediators act only on cells in the immediate environment.
Type of signaling? |
paracrine
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specialized cells secrete horomones that travel through blood vessels to influence target cells that may be lacated a considerable distance from the secreting cell. Type of signaling?
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endocrine
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What are the two distinguishable types of hormones?
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steroid and water soluble.
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How do the steroid hormones act?
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They can diffuse through the membrane so they diffuse and eventally make their way to intracellular receptors in the nucleus or the cytosol. The intracellular receptors act as transcription factors.
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How do the water soluble hormones act?
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They do not diffuse through the PM so they bind to cell surface receptors and relay their signal via a second messenger pathway.
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confined to the nervous system, cells secrete neurotransmitters at specialized junctions called synapses. Type of signaling?
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synaptic; this is a variation of paracrine signaling but exclusive to the nervous system.
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What types of cells are usually on the other side of the synaptic cleft receiving the diffused neurotrasmitter?
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neuron, epithelial cell, gland cell, or muscle cell.
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