Respiratory 6 - Lung cell biology

Question 1

How many generations of gas exchange units are there?

Answer 1

23

Question 2

What proportion of epithelial cells are goblet cells?

Answer 2

1/5

Question 3

Describe the role of Type II cells.

Answer 3

Produce SURFACTANT (so that lung does not collapse at low pressure on exhalation)
Also synthesise and secrete antiproteases
Make up 5% of alveolar surface
Precursor for Type 1 pneumocytes

Question 4

What is the role of Type I epithelial cells?

Answer 4

Gas exchange takes place through them

Question 5

What is the role of Type I epithelial cells?

Answer 5

Gas exchange takes place through them

Question 6

What do endosomes do in the lung cells?

Answer 6

They transfer solutes accross the blood-gas barrier.

Question 7

What are caveolae?

Answer 7

“little caves” - indentations in endothelial/epithelial cells where excoytosis happens - communication.

Question 8

Where is surfactant stored in epithelial type II cells?

Answer 8

In lamellar bodies

Question 9

How do surfactants look like and how do they work?

Answer 9

They are secreted as swirls. Then unravels to form a layer over the epithelium. Can form 9 layers for example.
Unused surfactant is stored in “the corners” of the alveolus as tubular myelin.

Question 10

What is surfactant made of?

Answer 10

10% protein - contains protein used in spreading and activity of surfactant
90% lipid, of which 90% is phospholipid. This enable polarisation at the apical surface.

Question 11

What are the 3 main structuresof pulmonary vasculature?

Answer 11

• muscular
• partially muscular (terminal bronchiole)
• non muscular (respiratory bronchioles)

Question 12

What happens to alveoli in someone with COPD (emphysema)?

Answer 12

No solid fill, holes appearing - loss of respiratory surface

Question 13

What happens in fibrosis?

Answer 13

The lungs attempt to repair but leads to scar tissue formation = fibrosis.
Lungs become solid

Type II cells multiply to repair damaged alveolar epithelium but also produce too much surfactant and stimulate fibroblast production of connective tissue (collagen deposit).
gas exchange = impossible

Question 14

How does oedema impair gas exchange (IV endotoxin)?

Answer 14

Oedema will form in between capillary and epithelial cell which takes away surface gas exchange.

Question 15

How do goblet cells and mucus change in smokers?

Answer 15

Goblet cells INCREASE in number
Secretions INCREASE in quantity
Secretions are THICKER

Question 16

What is the structure of mucus?

Answer 16

A thin sol phase overlays the cells

A thick gel phase is at the mucus-air interface

Question 17

What does mucus contain?

Answer 17

Mucin protein, proeoglycans, GAGs - give viscoelasticity
Serum derived proteins - albumin + alpha-1 antitrypsin + alpha-1 proteinase inhibitor
There are also antiproteases that have been secreted by the epithelia.
Anti-oxidants

Question 18

What proportion of epithelial cells are ciliated cells?

Answer 18

80%

Question 19

How do ciliated cells change in smokers?

Answer 19

Ciliated cell are severely depleted
Beat asynchronously
Ciliated cells found in bronchioles (though reduced in airways)
Unable to transport thickened mucus - smoker’s cough

Question 20

Give two characteristics of small airways.

Answer 20

< 2 mm in diameter

NOT cartilaginous

Question 21

What are clara cells?

Answer 21

Non-ciliated secretory epithelia found in the large, central and small airways and bronchi and bronchioles

Question 22

How are clara cells distributed throughout the respiratory system?

Answer 22

They increase in proportion distally

Question 23

What is the major role of clara cells?

Answer 23

Xenobiotic metabolism (ie drug metabolism)

Question 24

What are the two classes of enzymes produced by clara cells and what do they do?

Answer 24

Phase 1 and Phase 2 - they are meant to be involved in metabolising foreign substances but they are also implicated in oncogenesis.
Phase 1 enzymes convert procarcinogens to carcinogens
Phase 2 enzymes conjugate the carcinogens to make them inactive
Clara cells also produce antiproteases and lyoszyme.

Question 25

What are the diseases in COPD?

Answer 25

bronchitis + emphysema + small airways disease

Question 26

What do stromal fibroblasts do?

Answer 26

• make ECM
• make collagen and elastin to give alveolus elasticity and compliance
• divide to repair

Question 27

How do numbers of macrophages and neutrophils change in smokers and during infection?

Answer 27

Increase 5-10 fold

Neutrophils become more predominant than macrophage

Question 28

What do alveolar macrophages do and what proportion of total phagocytic cells in a normal lung consist of macrophages?

Answer 28

70% of total phagocytic cells in normal lung