Lecture 7: Lower airways and blood supply

Question 1

What is the respiratory zone compromised of?

Answer 1

1. Respiratory bronchioles
2. Alveolar ducts
3. Alveoli sacs
4. Alveoli

Question 2

Describe the alveoli;

Answer 2

Alveoli are in direct contact with the wall of a capillary. Majority of gas exchange. Distance is about 0.5um

Question 3

Describe the cells of the respiratory zone;

Answer 3

• Epithelium transitions towards respiratory zone into simple ciliated cuboidal which is interspersed with club cells. (prev. clara cells).
• Club cells -> Secretory cells with stem cell properties in lower airways.
• Transitions into AT1 and AT2 + Macrophages in alveoli

Question 4

Describe club cell secretion:

Answer 4

• Lipoproteins + antimicrobial properties + Markers of lung inflammation

Question 5

What are the 3 cell types of the alveoli and what are their functions?

Answer 5

1) AT1 -> 95% SA, squamous (Gas exchange)
2) AT2 -> Secrete surfactant, Dec Surface tension
3) Alveolar macrophage

Question 6

Whats the ECM of the alveoli?

Answer 6

ECM -> Collagen (structure) and Elastin (Elasticity)

Both produced by interalveolar fibroblasts

Question 7

Whats notable about the AT1 and Endothelium?

Answer 7

Fused basal lamina, reduces the blood-air barrier

Compromised by fluid or fibrosis

Question 8

What can defects in the CT lead to?

Answer 8

Loss of elasticity and destruction of alveoli = Emphysema

Up-regulation of collagen -> Fibrotic lung disease

Question 9

Whats the importance of elastin?

Answer 9

• Elastic fibres = recoil associated with tidal breathing

- Throughout lungs, particularly. bronchi and bronchioles and alveoli.

Question 10

Describe the interalveolar septum:

Answer 10

2 parts;

• Thin portion forms the blood air barrier
• Thick provides support between the alveoli and forms a route for pulmonary vessels (contains macrophages, fibroblasts and lymphatic vessels) - Imp fluid distribution

Question 11

describe the blood supply circuits of the lungs;

Answer 11

1. Pulmonary circulation - A low pressure conducting circuit, deoxy blood to alveoli for oxygenation which then returns to LA
2. Bronchial circulation - A high pressure circulation that supplies the tissues of the conducting zone.

Question 12

Describe the clinical relevance relating to elastin

Answer 12

Emphysema

• Reduction in elastin in lungs
• Increased inflam enzymes destroy elastin and collagen
• Destruction of CT
• Increased air spaces
• Increased compliance
• Reduced area for gas exchange
• Increased lung volume