lecture 14 - epithelia

Question 1

What are Epithelia?

Answer 1

• avascular tissues compose of cells, usually organised into sheets or tubules , attached to an underlying EC, basement membrane
• Cover both the internal and external surfaces of the body

Question 2

How are some epithelia modified?

Answer 2

modified to form glandular structures

Question 3

What are the 5 types of epithelia?

Answer 3

• simple
• stratified
• Columnar
• Cuboidal
• squamous

Question 4

What type of epithelial cellar kidney tubules made of

Answer 4

cuboidal

Question 5

What type of epithelial cells are the small intestine made of?

Answer 5

columnar

Question 6

What type of epithelial cells are the lung alveoli made of?

Answer 6

squamous

Question 7

What type of epithelial cells is the oesophagus made of?

Answer 7

stratified

Question 8

What are the 7 functions of the epithelia?

Answer 8

• Mechanical protection
• permeability barrier
• absorption
• filtration
• secretion
• Diffusion
• Sensory

Question 9

How are epithelia polarised?

Answer 9

• apical

- basal

Question 10

How are the epithelia polarised?

Answer 10

• biochemically polarised

Question 11

How is the physical integrity of the epithelium maintained?

Answer 11

Epithelia are held together by cell junctions

Question 12

What are cell junctions?

Answer 12

A specialised site on a cell at which it is attached to another cell or the extracellular matrix

Question 13

What is an anchoring junction?

Answer 13

linking cells together or to the extracellular matrix, maintain physical integrity

Question 14

What is an occluding junction?

Answer 14

seal the gaps between cells, prevent the leakage of water

Question 15

What is an channel - forming junction?

Answer 15

create passageways linking the cytoplasm of adjacent cells,

Question 16

What is an signal - relaying junction?

Answer 16

allows signals to be communicated from cell to cell of the nervous system

Question 17

Where are adherens junctions situated?

Answer 17

At the apical part of the cell

Question 18

What are the main components that adheren junctions are made up of?

Answer 18

• actin filaments
• cadherin
• a-catenin b-catenin

Question 19

Where are desmosome junctions situated?

Answer 19

below the adherens junction

Question 20

What are desmosome junctions made up of?

Answer 20

• intermediate filaments
• cadherin
• plakoglobin desmoplakin

Question 21

Purpose of the adherens junction

Answer 21

Adherens contain plaque which attaches to both membrane proteins and microfilaments of the cytoskeleton. Adherens help epithelial surfaces resist separation during various contractile activities

Question 22

purpose of desmosome junctions?

Answer 22

Link cadherins to intermediate filaments of the cytoskeleton

Question 23

purpose of focal adhesion junctions

Answer 23

Link cadherins to the actin filaments of the cytoskeleton

Question 24

What is the purpose of a hemidesmosome

Answer 24

Hemidesmosomes are multiprotein complexes that facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane.

Question 25

What are focal adhesions made up of?

Answer 25

- actin filaments - integrin - Focal adhesion kinase

Question 26

What are hemidesmosomes made up of?

Answer 26

- intermediate filaments - integrin/collagen dystonin

Question 27

What are the role of cadherins and where are they situated?

Answer 27

- mediate cell to cell attachment and hold them together | - They are found between cells in the plasma membrane

Question 28

What is a use of the adhesion belt associated with actin filaments?

Answer 28

- Causes invagination of the epithelial sheet caused by the tightening of the adhesion belt . - forms layers of cells and eventually an epithelial tube which can form many things such a neural tubes and even the brain

Question 29

What are the role of integrin molecules within hemidesmosomes

Answer 29

Play a role in mediating cell - matrix contacts , anchor the epithelial cells to the basal lamina

Question 30

What is keratin?

Answer 30

type of intermediate filament

Question 31

What is Pemphigus vulgaris an example of?

Answer 31

- autoimmune destruction of the desmosomal protein

Question 32

What does Pemphigus vulgarisms cause?

Answer 32

- severe blistering - dehydration and infection - potentially death

Question 33

What can occluding junctions be called?

Answer 33

Can be called an tight junction

Question 34

What do tight junctions/ occluding junctions do?

Answer 34

seal gaps between epithelial cells

Question 35

What are tight junctions/ occluding junctions made up of?

Answer 35

- Claudin and occludin | - Zona occluding scaffold protein

Question 36

What are the two functions of tight proteins?

Answer 36

- Barrier function (regulate passage of ions, water and macromolecules) - Fence function (Maintains cell polarity)

Question 37

How was it determined that occluding/ tight junctions help maintain cell polarity?

Answer 37

Take a fragment of epitheliem and placed in a aqeueos solution and then there is a tracer such as a salt Process the sample and look for the tracer Black area is the tracer , can only get so far to the tight junction

Question 38

What happens when there is a loss of barrier function In tight junctions?

Answer 38

Crohns disease - inflammation of the bowels , permeability disorder

Question 39

What happens when there is a loss of fence function in tight junctions?

Answer 39

Cancer - Loss of cell polarity and cell contacts (epithelial-mesenchymal transition - EMT), increase in motility and eventual metastasis

Question 40

What do gap junctions do?

Answer 40

- allow ions and small molecules to pass directly from cell to cell

Question 41

What are gap junctions made up of?

Answer 41

- 6 connexins form a connexon - 1 connexon pairs up with a connexon in another cell - They are organized as patches where you gave lots of connexons - The connexons can open and close

Question 42

What happens when there are abnormal gap junctions and what are the human inherited disorders?

Answer 42

- cataracts | - Vohwinkel syndrome

Question 43

What are the names of channel forming junctions in plants called?

Answer 43

- plasmodesmata

Question 44

What are the roles of neuralgia and neurexin in the synapse?

Answer 44

Neurexins and neuroligins are synaptic cell-adhesion molecules that connect pre- and postsynaptic neurons at synapses

Question 45

What is the role of cadherin in the synapse?

Answer 45

Also helps to hold the cells together

Question 46

What is Myasthenia Gravis?

Answer 46

- autoimmune destruction of the neuromuscular junction | - first indication is a droopy eye

Question 47

What are epithelia?

Answer 47

Epithelia are avascular tissues composed of cells, usually organised into sheets or tubules, attached to an underlying ECM basement membrane