ILS6-epithelial tissue

Question 1

Functions of the Epithelial Tissue (7)

Answer 1

1. Protection or barrier (epithelial cells of the
   skin)(ILS-4 HDM)
2. Absorption (epithelium in liver, intestines, and
   lungs)
3. Secretion (epithelial tissue in glands secrete
   enzymes, hormones, and fluids)
4. Excretion and transport (epithelial tissue in the
   kidney and sweat glands)
5. Filtration (epithelium in the kidney and
   respiratory system)
6. Contractility (Myoepithelial cells)
7. Sensory reception (Taste buds of the tongue,

Question 2

what is the basement membrane (BM) of epithelial tissue compossed of?

Answer 2

basal lamina + reticular lamina

Question 3

basal lamina contains____

Answer 3

a thin meshwork of type IV collagen (ILS-7) and laminin associated with proteoglycans and glycoproteins, secreted by epithelial
cells

Question 4

reticular lamina contains ____

Answer 4

type III collagen and anchoring fibrils of type
VII collagen, secreted by fibroblasts

Question 5

function of Basement membrane

Answer 5

• attach epithelia to connective tissue
• provide a guide or scaffold during tissue regeneration after injury
• compartmentalize epithelial cells from other tissues
• filter substances passing from connective tissue into epithelia
• Prevent tumor metastasis

Question 6

below the Basement membrane you find the _____

Answer 6

Lamina propria is a thin, irregular connective tissue

Question 7

special function of basement membrane in kidney

Answer 7

filter

Question 8

Microvilli

Answer 8

short membrane projections with cores of actin filaments
* increase epithelial cells’ apical surface area for absorption (intestine)

Question 9

• Stereocilia

Answer 9

• Long microvilli with specialized mechanosensory functions in cells of the
  inner ear and for absorption in tissues of the male reproductive tract

Question 10

Cilia

Answer 10

• larger projecting structures
• has a well-organized core of microtubules (in a 9 + 2 arrangement called
  the axoneme) in which restricted, dynein-based sliding of microtubules
  causes ciliary movement that propels material along an epithelial surface

Question 11

The internal structure of microvilli

Answer 11

The internal structure of microvilli contains a core of
actin that is cross-linked by actin-bundling proteins

Question 12

what are the Actin-bundling proteins:

Answer 12

Actin-bundling proteins: fascin, espin, and fimbrin FEF

Question 13

what anchors the actin of microvilli to the membrane

Answer 13

tip of head is anchored by villin

Myosin I: binds the actin to the plasma membrane of the microvillus
* Myosin II and tropomyosin of the terminal web (TW)
explain its contractile ability
* The TW is composed of actin filaments stabilized
by spectrin, which also anchors the TW to the apical cellmembrane

Question 14

stereocilia

Answer 14

immotile microvilli

Question 15

where is stereocilia found ?

Answer 15

• Limited to the epididymis, the proximal part of
  the ductus deferens of the male reproductive
  system, and the sensory (hair) cells of the
  inner ear
• Stereocilia of the genital ducts are extremely
  long processes that extend from the apical
  surface of the cell and facilitate absorption
• Stereocilia of the sensory epithelium of the
  ear are sensitive to mechanical vibration and
  serve as sensory mechanoreceptors
• Stereocilia can be easily damaged by
  overstimulation, so they have a molecular
  mechanism to continuously renew their structure

Question 16

stereocilia of epididymis are ______

Answer 16

long

Question 17

stereocilia are anchored to the memebrane by

Answer 17

Ezrin (myosin 1 and 1 in microvilli)

no villin

Question 18

cilia

different types of cilia

Answer 18

Cilia
* Hair-like extensions of the apical plasma membrane containing an axoneme

Question 19

different types of cilia

Answer 19

• Motile cilia are on the apical side of
  epithelial cells
• Primary cilia (monocilia) are solitary
  immotile projections on almost all
  eukaryotic cells
• Nodal cilia are in the embryo on the
  bilaminar embryonic disc at the time of
  gastrulation

Question 20

Motile cilia

Answer 20

Motile cilia are on the apical side of
epithelial cells

Question 21

• Primary cilia (monocilia)

Answer 21

are solitary
immotile projections on almost all
eukaryotic cells

-function as chemosensors, osmosensors,
and mechanic sensors
- mediate light sensation, odorant, and
sound perception

Question 22

• Nodal cilia

Answer 22

_____are in the embryo on the
bilaminar embryonic disc at the time of gastrulation

• play an important role in early embryonic development
• perform clockwise rotational movement

Question 23

what is the structure of Cilia?

Answer 23

Axoneme- microtubule based structure, extends from the basal body

a centriole-derived, microtubule-organizing center (MTOC) located in
the apical region of a ciliated cell

microvili and cilia look similar under microscope

• ciliary apparatus= basal bodies + basal body–associated structures
• Motile cilia and their counterparts, flagella, possess a typical 9 + 2
  axonemal organization with microtubule-associated motor proteins
  generating forces needed to induce motility

Question 24

Epithelial intercellular junctions
* Lateral cell-to-cell junctions (3)

Answer 24

Tight or occluding junctions:

Adherent junctions or desmosomes

Gap or communicating junctions

Question 25

Tight or occluding junctions:

Answer 25

interacting transmembrane proteins (claudin and occludin) prevents intracellular passage

Question 26

Adherent junction or desmosomes

Answer 26

formed by the cadherin, strong sttachement between epithelium may form zonula adherens encircling epithelial cells just below their tight junctions and attach indirectly to actin filaments or scattered, spot-like attachment sites called desmosomes or maculae adherens, which attach to keratin* intermediate filaments

Question 27

Gap or communicating junctions

Answer 27

points of cell contact where both plasma membranes have hexameric complexes of transmembrane connexons, each forming a channel (pore) allowing passage of small molecules from one cell to the other

Question 28

epithelial Basal surface junction

Answer 28

Basal surface junction * Hemidesmosomes composed of transmembrane integrins attach cells to proteins of the basal lamina

Question 29

Tight junctions (TJ) fuction

Answer 29

Allow epithelial cells to function as a barrier * Form the primary paracellular diffusion barrier between adjacent cells * Limit the movement of ions, water, and other macromolecules through the intercellular space * Act as fences to prevent the migration of lipids and specialized membrane proteins between the apical and lateral surfaces * Maintain cell polarity and integrity of the apical and lateral surfaces * Recruit signaling molecules to the cell surface and link them to the actin filaments of the cell cytoskeleton

Question 30

Helicobacter pylori damages

Answer 30

binds the extracellular domains of tight-junction proteins in cells of the stomach and inserts a protein into these cells, which targets (Zona Occludin-1) ZO-1 and disrupts signaling from the junction leads to gastric ulcers

Question 31

Pemphigus vulgaris

Answer 31

autoimmune skin disorder where IgG targeting desmoglein leads to dissolution of the desmosomes, fluid accumulation, and epidermal cells detach – Symptoms: painful blisters and sores in the mouth, skin blisters – Treatment: corticosteroids, immune suppressants, plasmapheresis or immunoglobulins

Question 32

Bullous Pemphigoid:

Answer 32

rare autoimmune skin disorder where IgG (antibody) targets hemidesmosomes, specifically type XVII collagen, causing the epidermis to detach from the basement membrane, causing blistering

Question 33

gap junctions

Answer 33

consists of an accumulation of transmembrane channels or pores * present in epithelia, smooth and cardiac muscle, and nerves * permit the direct passage of signaling molecules from one cell to another * important in tissues in which the activity of adjacent cells must be coordinated, such as epithelia * engaged in fluid, electrolyte, small metabolites transport, vascular and intestinal smooth muscle, and heart muscle

Question 34

what microorganism damages the tight junction s

Answer 34

Clostridium perfringes -its enterotoxin binds to claudin of tight junction and messes up its maintence causes fliud loss Helicobacter Pylori, target the Zona occludin and disrupt the signaling from the junction, leads to gastric ulcers