6 - Lung Cell Biology

Question 1

What effect does dichotomous branching have on the resistance of the airways?

Answer 1

resistance to airflow decreases massively down generations

Question 2

Cilia have _____ beating

Answer 2

metachronous

Question 3

What is the function of cilia (in relation to mucus)?

Answer 3

pushes the mucus towards the epiglottis, which is usually swallowed or expectorated (coughed up/spat out)

Question 4

give some features of what happens to the small airways during COPD

Answer 4

• mucus becomes trapped
• airways narrow
• the walls are broken down by enzymes and inflammatory cells - this reduces peripheral gas exchange

Question 5

Which airways are enriched in clara cells?

Answer 5

bronchi and bronchioles

Question 6

What is COPD?

Answer 6

bronchitis + emphysema + small airways disease

Question 7

What are the 2 types of cells in the alveolar walls?

Answer 7

Type I and type II

Question 8

Describe type I cells?

Answer 8

long thin cells (used in gas exchange)
the alveolar wall takes on the shape of the underlying blood vessels
‘like a friend egg on a mesh’

cover 95% of the alveolar surface

Question 9

Describe the function of type II cells

Answer 9

• contain lamellar bodies that store surfactant
• synthesise and secrete antiproteases
• precursors for alveolar epithelium types I cells (they divide and differentiate to replace damaged type I cells)

Question 10

Where are type II cells?

Answer 10

• only found in the alveolar wells
• positioned in the corners of the alveoli and are embedded in the interstitium
• very close to capillaries

Question 11

What are caveolae?

Answer 11

lipid-rich craters in the plasma membrane with roles in exocytosis
come from both types of cells and acts as messengers between both types of cells

Question 12

What are the components of surfactant?

Answer 12

10% PROTEINS
- contains the surfactant-associated proteins that are important in spreading and activity of surfactant

90% LIPID

• of which 90% is phospholipid.
• the phospholipid is amphipathic (it has lipophilic and hydrophilic regions), enabling polarisation at the epithelial surface and surface tension reducing activity.

Question 13

What type of cell forms around 70% of total phagocytic cells in the normal lung?
Where are they found?

Answer 13

alveolar macrophage

enriched in the lower respiratory tract but found throughout

Question 14

What is the role of alveolar macrophages?

Answer 14

• scavenging cells (phagocytose)
• send messages to other inflammatory cells during infection
• secrete proteases to digest unwanted debris
• generate oxidants during phagocytosis to help clear infection
• generate antioxidants to neutralise oxidants (after infection of any that may have been inhaled)
• contains enzymes that metabolise toxicants

Question 15

Describe the distribution of polymorphonuclear neutrophils in normal, smokers and infected people

Answer 15

• usually only about 5% of LRT phagocytes
• increase in smokers and during infection
• there is a high proportion in the large airways

Question 16

What is the function of polymorphonuclear neutrophils?

Answer 16

contain high levels of potent proteases in granules which are released on activation

Question 17

What 5 type of cells do the alveolar units contain?

Answer 17

• type I cells
• type II cells
• stromal fibroblasts
• alveolar macrophages
• capillary endothelium