What causes cystic fibrosis?

1
What causes cystic fibrosis?

• A mutation in the cystic fibrosis transmembrane
  regulatory protein

2
What does the CFTR protein do?
It helps control the viscosity (or stickiness) of
mucus that lines the epithelial cells of the
airways, digestive and reproductive systems
mucus
cilia
epithelial cell
If the mucus in airways is
too sticky the cilia cannot beat and remove the
mucus, which then clogs up airways
too runny the mucus can flood the airways
3
When there is excess water in the mucus
Water is drawn out of the mucus and it thickens
Na
Cl-
H2O
mucus
2
5
apical membrane
CFTR channel closed
Na channel open
H2O
pump
1
basal membrane
4
3
tissue fluid
H2O
Na
Cl-
4
When there is too little water in the mucus
Water is drawn out of the mucus and it becomes
less sticky
Cl-
Na
Na
mucus
3
2
4
apical membrane
Na channel closed
CFTR channel open
The CFTR somehow blocks the sodium channels
H2O
Cl-
1
H2O
basal membrane
5
pump
tissue fluid
H2O
Na
5
With cystic fibrosis
The mucus becomes very thick and sticky
Cl-
Na
H2O
mucus
1
2
3
X
apical membrane
The CFTR protein cannot block the sodium channels
so they are always open
CFTR non- functional
Water drawn out by osmosis
Na channel open
H2O
basal membrane
tissue fluid
H2O
Cl-
6
How cystic fibrosis affects the lungs
Sticky mucus builds up in the airways, reducing
flow of air into alveoli. Lungs gradually fill up
with mucus, making them less effective for gas
exchange.

• Symptoms
• Severe coughing - to remove excess mucus.
• Breathlessness - shortage of oxygen increases
  tiredness and lack of energy
• Infections - as bacteria are trapped in mucus

7
How does cystic fibrosis affect the reproductive
systems?
Men Women
Sperm duct is blocked and prevents movement of sperm During the menstrual cycle the levels of mucus vary.
Can lack the sperm ducts Women with CF have thick levels of mucus which can block the cervix so sperm cannot reach them.
8
How cystic fibrosis affects the digestive system
Thick, sticky mucus blocks the pancreatic duct
preventing enzymes from reaching the
duodenum.Food is not digested and absorbed
sufferers fail to put on body mass and suffer
malnutrition. Trapped digestive enzymes damage
the pancreatic cells affecting cells producing
insulin resulting in diabetes.