ICL 1.0: Epithelium Flashcards

Question

what is stratified squamous non-keratinized epithelium?

Answer 1

in this type of epithelium, the apical cells are squamous, but do not undergo keratinization this epithelium forms a relatively tough, impermeable barrier it is seen in the esophagus and the vagina

Answer 2

in keratinized epithelium, cells undergo a process of differentiation as they migrate to more apical layers --> in the course of this differentiation process, cells acquire more cytoskeletal elements, create more intercellular links, and extrude a material which creates a water impermeable barrier by the time these cells reach the most apical layers, they have lost all of their organelles, including their nuclei this process is called keratinization or cornification! in the epithelial component of skin, the epidermis, stratified squamous, keratinized epithelium acts as an effective barrier against water loss, and protects against the abrasive external environment

Answer 3

they are both not very permeable they are found lining some ducts, which act as conduits rather than modifying a secretory product such ducts are found in sweat glands and in mammary glands

Answer 4

it looks like fluffy pillows it's only seen in excretory passages of the urinary tract it protects underlying tissues from the components of urine and accommodates for rapid volume changes

Answer 5

changing environmental conditions may change the signals that are sent to epithelial stem cells -- this causes the stem cells to produce a different type of epithelial cell the process of metaplasia, therefore, does not result from transformation of one mature cell type into another mature cell type; instead, it occurs at the point where cells are produced by a given stem cell an example of metaplasia is seen in respiratory tract epithelium subjected to chronic irritation, such as results from smoking -- under these conditions, the lining epithelium may change from pseudostratified ciliated columnar epithelium to the tougher stratified squamous, non-keratinized epithelium although in this process the respiratory tract gains the protective effects of stratified squamous epithelium, because the metaplastic epithelial cells have no cilia, and because goblet cells have been lost, the respiratory tract loses the benefits of the mucociliary escalator

Answer 6

1. occluding junction 2. anchoring junction 3. communication junction

Answer 7

1. transmembrane proteins 2. cytoplasmic proteins 3. cytoskeletal attachment 4. size of intercellular space

Answer 8

aka tight junction these junctions are the MOST apical junction between two cells and regulate what gets through the cell junction the transmembrane proteins form strands, which fuse at discreet points (“kisses”), occluding the intercellular space at those points the zonula occludens is formed by the fusion of two different classes of transmembrane proteins: claudins and occludins the claudins and occluding are then linked to a variety of cytoplasmic proteins which in turn are linked to actin cytoskeletal protein

Answer 9

the tight junction establishes an apical and basal compartment it limits the mobility of membrane proteins like transport proteins or receptors so that they are restricted to the apical or basal region of the cell this creates functional differences between the apical and basal regions of the cell, and of the tissue as a whole ex. epithelial cells may have specialized proteins for transporting glucose across the apical membrane, and have other proteins for the transport of ions on the basal membrane they also act like a gate a regulate the passage of lateral between cells establishing a permeability barrier across the epithelial sheet --> large molecules can't get through the small pores created by strands of claudins ut small ones probably can get through

Answer 10

1. claudins | 2. occludins

Answer 11

1. cell to cell = they link the cytoskeleton of one cell to the cytoskeleton of adjacent cells zonula adherent and macula adherens 2. cell to basal lamina = link the cytoskeleton of a cell to the underlying basal lamina hemidesmosome and focal adhesion

Answer 12

they provide structural support and strength they act as points of mechanical attachment between adjacent epithelial cells and between epithelial cells and the underlying tissue they are more prominent in epithelium which is subjected to relatively large shear forces, such as the epidermis of the skin

Answer 13

the zonula adherens is ALWAYS just basal to the zonula occludens it's a band that provides a lot of structural support and anchor two cells together a zonula adherens is required for the formation of an occluding junction E-cadherins are the transmembrane proteins that bind to the cytoplasmic proteins and form an intracellular plaque composed of vinculin and actinin these cytoplasmic proteins are bound to actin filaments in the apical region of the epithelial cell --> the resulting band of actin is called the terminal web

Answer 14

E-cadherin these are glycoproteins that are Ca dependent members of the cadherin family they bind to catherine of an adjacent cell and form a strong mechanical link --> the resulting intercellular space includes regions for Ca binding the cytoplasmic proteins are the vinculin and actinin

Answer 15

aka desmosome! it's a spot of strong cell-cell adhesion but it's not a band so it won't always be seen in section they look like multiple little spot welds that extend all the way down the two cells however, you don't see the terminal web like you do with zonula adherens

Answer 16

a grouping of intercellular junctions common to all epithelial sheets this grouping includes: 1. occluding junctions 2. zonula adherens 3. macula adherens ZO-ZA-MA

Answer 17

they link an epithelial cell to its underlying basal lamina transmembrane proteins = integrins which interact with the laminin and type IV collagen of the basal lamina cytoplasmic proteins form a plaque and are linked to intermediate filaments of the cytoskeleton

Answer 18

aka gap junctions transmembrane proteins, called “connexins”, of one cell align and bind to transmembrane proteins of the adjacent cell to form a pore, called the “connexon” small, water-soluble molecules (ions, some cytokines) can pass from one cell to another through these communicating junctions

Answer 19

1. microvilli | 2. cilia

Answer 20

1. lateral infoldings | 2. basal inholdings

Answer 21

finger-like projections which extend from the apical surface of the cell individual microvilli cannot be resolved in light microscopy, but can be seen in EM used to increase surface area or move material over the apical cell surface

Answer 22

1. glycocalyx 2. actin 3. terminal web microvilli have an actin core which goes down and interacts with the terminal web they also have a glycocalyx which is rich in enzymes and helps break stuff down or speed up reactions which is important in the GI tract for example

Answer 23

yes contraction of the terminal web which is connected to the actin core of the microvilli can cause the microvilli to move!

Answer 24

very large microvilli as with other microvilli, stereocilia increase the apical cell membrane surface area, allowing for increased absorption stereocilia are found in the cochlea of the ear and the epididymis* of the male reproductive tract

Answer 25

motile structure on the apical side of epithelial cells that help move material across an epithelial surface like through the lumen of an airway

Answer 26

they increase surface area basal infoldings are really common in epithelial cells which are engaged in ion transport across the basal cell membrane, such as in renal tubule cells