MCB Lecture 36 Epithelial Tissue

Question 0

Define tissues

Answer 0

Coordination of cell types

Question 1

Define organs

Answer 1

Coordination of tissues

Question 2

What are the different types of tissue? (5)

Answer 2

Epithelial
Connective
Blood/lymphatic
Muscle
Nervous

Question 3

Where is epithelial tissue found?

Answer 3

Lining external and internal surfaces and ducts

Question 4

What are the different morphologies of epithelial tissues?

Answer 4

Simple
Stratified
Pseudostratified

Columnar
Cuboidal
Squamous

Question 5

What type of morphology are the epithelial cells in blood vessels?

Answer 5

Simple squamous

Question 6

What type of morphology are the epithelial cells in intestine?

Answer 6

Simple columnar

Question 7

What type of morphology are the epithelial cells in skin?

Answer 7

Stratified squamous

Question 8

What type of morphology are the epithelial cells in the respiratory tract?

Answer 8

Ciliated pseudo stratified

Question 9

Describe how the epithelium in the respiratory tract provides protection

Answer 9

The cells secrete mucous that traps dirt and detritus.

The cilia beat up, moving the mucous up to the mouth where it is swallowed and excreted

Question 10

What are two genetic mutations that cause problems in the respiratory epithelium?

Answer 10

1. Mutation in Dynein, preventing the cilia from beating

2. Cystic fibrosis: ion channel mutation, mucous is too thick to be moved up

Question 11

Describe the function of the epithelium in the digestive tract

Answer 11

Villi to increase surface area
Absorption of nutrients at apical end: active transporter
Basal end: passive transporters, nutrients move down diffusion gradient into the blood stream

Question 12

Describe the polarisation of epithelial cells

Answer 12

The position of the nucleus

Also, apical end and basal end

Question 13

What are the different types of cell junctions? (5)

Answer 13

1. Tight
2. Gap
3. Adherens
4. Desmosomes
5. Focal adhesions
6. Hemi desmosomes

Question 14

Where are tight junctions localised?

Answer 14

Near the apical region of a cell

Question 15

What is the function of tight junctions?

Answer 15

They prevent movement of materials between two cells

Question 16

Describe the structure of tight junctions

Answer 16

Interaction between the proteins on the two adjacent cells
Claudin
Occludin

Question 17

What is the function of Claudin and occludin?

Answer 17

These are the proteins presented on the outermembrane of cell that form tight junctions, preventing movement of materials between cells

Question 18

What is the function of Adherens junctions?

3

Answer 18

1. Sticks cells together
2. Epithelial folding
3. Cell sorting

Question 19

Describe the structure of Adherens junctions. Which protein is involved?

Answer 19

Classical cadherin proteins are involved. The cadherins on adjacent cells interact at the N terminus
Linker proteins connect the cadherins to the actin filaments inside the cell

Question 20

Between which two things are Adherens junctions present?

Answer 20

Two cells

Question 21

Cadherin interaction is … dependent

Answer 21

Calcium

Without calcium, the cadherin chains are floppy and can’t interact with the cadherins of the adjacent cell

Question 22

What are junctional complexes?

Answer 22

These are the localisation of certain types of junctions in certain regions

A single cell can have different types of junctions

Question 23

How does cadherin interact with the cell membrane and actin?

Answer 23

Through linker proteins

Question 24

How do two cadherins interact?

Answer 24

At the N terminus

Question 25

What are some of the linker proteins that connect cadherin to actin

Answer 25

Catenins | Alpha and beta

Question 26

Describe the process of epithelial folding

Answer 26

There is a belt of actin and Adherens junctions in the apical region of cells This belt contracts, and an invagination forms This pinches off to form a tube

Question 27

Describe Adherens junctions role in cell sorting

Answer 27

Cells presenting Adherens junctions will stick together | In this way, certain cells are grouped together

Question 28

Which cell secretes mucus into the respiratory lumen?

Answer 28

Goblet cells

Question 29

The epithelium in which two organs is important for absorption?

Answer 29

Kidneys | Small intestine

Question 30

What are some generally features of the apical region of epithelial cell?

Answer 30

Absorption Secretion Ciliation

Question 31

What are some generally features of the basal end of epithelium?

Answer 31

Adhesion to ECM Diffusion of materials Secretion into sub mucosa

Question 32

In polarised cells, organelles are ...

Answer 32

Differentially distributed, polarised

Question 33

How do tight junctions affect the polarity of membranes?

Answer 33

It separates the different ends of the membrane. | Eg. The cilia and the basal end

Question 34

Which junction is vital for the apical-basolateral polarity?

Answer 34

Tight junctions

Question 35

What sort of binding is there between Claudin and occludin in tight junction?

Answer 35

Non covalent

Question 36

The more tight junction proteins, ...

Answer 36

The more impermeable

Question 37

Why are Adherens junction said to be homophobic?

Answer 37

Interaction between with of the same molecule, classical cadherin

Question 38

What gives skin it's high tensile strength?

Answer 38

Hemidesmosomes

Question 39

Integrins will not engage ECM unless...

Answer 39

There is signalling Eg. Activation of tallin

Question 40

Outside - in signalling in focal adhesions requires other kinases because ... What are these other kinases?

Answer 40

Because the integrins don't have kinase regions FAK

Question 41

Describe the tissue structure of the alimentary tract

Answer 41

``` Columnar epithelium Basement membrane Connective tissue (fibroblasts, collagen etc) Muscle layer Connective tissue Surrounding layer of epithelium ```

Question 42

What is transitional epithelium?

Answer 42

This is epithelium that has a different appearence depending on the state of the organ. Ie, it can look squamous when stretched and cuboidal in the unstretched state

Question 43

What is pseudo stratified epithelium?

Answer 43

All the cells connect to the basement, however, not all cells extend to the apical surface

Question 44

What are the cell types in the respiratory tract?

Answer 44

``` Nucleates cells Goblet cells (mucous secreting) Basal cells (stem cells) ```

Question 45

What type of epithelium is the thyroid?

Answer 45

Simple cuboidal

Question 46

What type if epithelium is the bladder?

Answer 46

Transitional

Question 47

What is the name of the disorder in which the cilia are immobile?

Answer 47

Kartagener's syndrome

Question 48

A Claudin molecule in a tight junction bonds ... with a ... molecule

Answer 48

Non-electrostatic ally Claudin

Question 49

Which junctions are important for organogenesis?

Answer 49

Adherens junctions: epithelial folding and cell sorting

Question 50

Which cadherin family proteins are present in Desmosomes?

Answer 50

Desmoglein | Desmocollin

Question 51

Describe which junctions intermediate filaments connect to, and how they do so

Answer 51

Desmosomes: connects to the side of intermediate filaments Hemidesmosomes: connects to the ends of intermediate filaments

Question 52

What are the linker proteins in Desmosomes?

Answer 52

Desmoplakin Plakoglobin Plakophilin

Question 53

How does inside out signalling affect outside-in signalling?

Answer 53

Once an ECM protein has been engaged through inside-out signalling, outside in signalling occurs

Question 54

What sort of processes does outside-in signalling result in?

Answer 54

Change in gene expression: - migration - differentiation - proliferation