Epithelial tissue

Question 1

four basic tissue types

Answer 1

epithelial, connective, muscular, and nervous tissues

Question 2

what are connective, muscle and nervous tissue characterized by

Answer 2

connective- abundant ECM
muscle- elongated cells for contraction/movement
nervous- cells with long fine processes specialized to receive, generate and transmit impulses

Question 3

stroma is always connective tissue except where?

Answer 3

brain and spinal cord

Question 4

what are epithelial cells composed of

Answer 4

aggregated polyhedral cells adhering to each other and thin layer of ECM, forming sheets lining organs

Question 5

which tissues line all external and internal surfaces of the body and all substances that enter or leave an organ must cross this type of tissue

Answer 5

epithelia

Question 6

what are the principal functions of epithelia

Answer 6

• Covering, lining, and protecting surfaces (eg, epidermis)
• Absorption (eg, the intestinal lining)
• Secretion (eg, parenchymal cells of salivary glands)

Question 7

give examples of epithelia that may be specialized sensory cells

Answer 7

taste buds or the olfactory epithelium

Question 8

true or false, Most epithelia are adjacent to connective tissue containing blood vessels from which the epithelial cells receive nutrients and O2

Answer 8

true, even thick epithelia

Question 9

how are epithelial cells organized

Answer 9

polar, organelles and membrane proteins distributed unevenly

Question 10

what is the basal and apical pole

Answer 10

basal- region of the cell contacting the ECM and connective tissue
apical- opposite end, usually facing a space

Question 11

what do the basal surface of all epithelia rest on

Answer 11

a thin extracellular, a semipermeable filter for substances reaching epithelial cells from below

Question 12

what two parts of the basement membrane can be seen with a TEM

Answer 12

Nearest the epithelial cells is the basal lamina, a thin, electron dense, sheet-like layer of fine fibrils, and beneath this layer is a more diffuse and fibrous reticular lamina

Question 13

what do the ECM components of the of the basal lamina include

Answer 13

• Type IV collagen
• Laminin
• Nidogen and perlecan

Question 14

how is laminin organized in the ECM

Answer 14

large glycoproteins that attach to integrins and project through the mesh formed by the type IV collagen

Question 15

how are Nidogen(rod-like protein) and perlecan (proteoglycan) organized in the ECM

Answer 15

cross-link laminins to the type IV collagen network–3D structure to bind epithelium to the surface and determine porosity and size of molecules filtered

Question 16

what does the more diffuse meshwork of the reticular lamina contain

Answer 16

type III collagen and is bound to the basal lamina by anchoring fibrils of type VII collagen, both prod by connective tissue cells

Question 17

functions of the basement membrane

Answer 17

• filters
• support for epithelia
• components organize integrins, maintaining polarity and localize endocytosis, signal transduction
• cell to cell interactions
• scaffold–repair and regeneration

Question 18

what junctions are present in epithelia

Answer 18

• Tight or occluding junctions form a seal
• Adherent or anchoring junctions–adhesion
• Gap junctions–communication

Question 19

what are tight junctions also known as and how do they work

Answer 19

zonulae occludentes (zonula occludens is the singular form) most apically located junction and form belt around circumferance of cell

Question 20

what causes seal

Answer 20

due to tight interactions between the transmembrane proteins: claudin, occludin, nectins, and junctional adhesive molecules [JAMs]

Question 21

these bind to actin and provide stability
• Occludin interacts with four major _____________ proteins: _________________.
• Nectins are connected to ___________ through the protein _____.
• Claudin (Latin claudere, to close), a family of 24 proteins forming __________ in the tight junctions, form a water channel for ________________.
• Junctional ______________ [JAMs]

Answer 21

these bind to actin and provide stability
• Occludin interacts with four major zonula occludin (ZO) proteins: 1, ZO-2, ZO-3, and afadin.
• Nectins are connected to actin filaments through the protein afadin.
• Claudin (Latin claudere, to close), a family of 24 proteins forming linear fibrils in the tight junctions, form a water channel for paracellular absorption.
• Junctional adhesive molecules [JAMs]

Question 22

what bacteria binds to claudin (Zonula occludens proteins) molecules in intestinal cells preventing tight junctions–cell death

Answer 22

Clostridium perfringens secreting Enterotoxin causing food poisoning.
loss of tissue especially along intestinal lumen

Question 23

what does Helicobacter pylori do to tight junction proteins

Answer 23

binds to tight junction proteins in stomach cells, and disrupts the connection by introducing a protein that targets ZO-1

Question 24

what is a form of adherens junction also called

Answer 24

zonula adherens, anchoring cell to its neighbors

Question 25

what mediates cell adhesion

Answer 25

E-cadherins, transmembrane glycoproteins, binding to each other in presence of Ca

Question 26

what do cadherins bind to at their cytoplasmic ends

Answer 26

catenins that link to actin filaments, forming terminal web

Question 27

how are Fascia adherens different from zonula and give an example of where they are used

Answer 27

does not go around the entire circumference of the cell.

in Cardiac muscle cells

Question 28

what are desmosomes also called

Answer 28

they are macula adherens which are also anchoring junctions (doesnt form a belt)

Question 29

what is in between the cells in desmosomes

Answer 29

desmocollins and desmogleins which form bonds in presence of calcium

Question 30

what is the outer dense plaque that is closely adhering to the cytoplasmic aspect of the plasmalemma composed of

Answer 30

glycoproteins plakoglobins and plakophilins held together by proteins known as desmoplakins (which then bind intermediate filaments)