Basement Membrane

Question 1

How do epithelial cells bind to the basement membrane?

Answer 1

They physically bind via focal adhesions and hemi-desmosomes

Question 2

How does the basement membrane influence the epithelium?

Answer 2

1. it controls the growth and differentiation of epithelium

2. it acts as a barrier to downwards epithelial growth

Question 3

In what disease is the barrier to downwards epithelial growth compromised?

Answer 3

Cancer

Once the epithelium grows through the basement membrane, it becomes malignant

Question 4

How does the basement membrane control the flow of nutrients?

Answer 4

It acts as a selective barrier

It controls the flow of nutrients, metabolites and other molecules to and from the epithelium

Question 5

What are the three layers of the basement membrane?

Answer 5

1. lamina lucida
2. lamina densa
3. lamina reticularis

Question 6

What is found in the lamina lucida?

Answer 6

1. integrins
2. laminins 1, 5, 6, 10
3. collagens XVII and IV
4. dystroglycans

Question 7

What is found in the lamina densa?

Answer 7

1. Collagen IV
2. entactin/nidogen
3. perlecan
4. heparin sulfate proteoglycans

Question 8

What is found in the lamina reticularis?

Answer 8

1. collagens, I, III, V

2. proteoglycans

Question 9

What is heparin sulphate in the basement membrane?

Answer 9

It is a component of the ECM which is covalently attached to core proteins to form a proteoglycan

Question 10

Which 2 layers of the basement membrane make up the basal lamina?

Answer 10

Lamina lucida and lamina densa

Question 11

What is the major component of the basement membrane and what is it involved in?

Answer 11

Type IV collagen

Involved in cell adhesion, migration, differentiation and growth

Question 12

What does type IV collagen form in the basement membrane?

Answer 12

It anchors fibrils and fibrillin microfibrils when connective tissue attaches to the basal lamina

Question 13

What does degradation of type IV collagen in the basement membrane lead to?

Answer 13

1. angiogenesis
2. tissue remodelling
3. cancer progression

Question 14

What is fibronectin?

Answer 14

A glycoprotein found in the extracellular matrix

Question 15

What will fibronectin bind to?

Answer 15

Membrane-spanning receptor proteins called integrins

Question 16

What is the role of fibronectin?

Answer 16

It binds extracellular matrix components such as collagen, fibrin and heparin sulphate proteoglycans

Question 17

What process does fibronectin influence?

Answer 17

It is involved in cell adhesion, growth, migration and differentiation

Question 18

How is cellular fibronectin assembled?

Answer 18

It is assembled into the ECM

This is an insoluble network that separates and supports the organs and tissues in an organism

Question 19

What are laminins involved in?

Answer 19

Formation, structure and stability of the basement membrane

Question 20

What is a laminin?

Answer 20

A type of glycoprotein which is involved in the structural scaffolding of tissues

Question 21

How do laminins perform their function?

Answer 21

They can separate or connect different tissues

They can also bind to cells and anchor organised tissue cells to the membrane

Question 22

What is the role of nidogen-1?

Answer 22

It is a glycoprotein that interacts with other components of the basement membrane

It can play a role in cell interactions with the ECM

Question 23

What will bind to the mesh of type IV collagen in the basement membrane?

Answer 23

Laminin and nidogen

Question 24

What is the importance of laminin and nidogen binding to IV collagen?

Answer 24

This provides a link to the integrins (laminin receptors) on epithelial cells to produce a hemidesmosome

Question 25

How does a focal adhesion form?

Answer 25

Type II collagen binds to fibronectin

Fibronectin links to integrins on epithelial cells

Question 26

Why are the hemidesmosomes and focal adhesions important?

Answer 26

They link the basement membrane to epithelial cells and act as a form of cell communication