Respiratory zone

Question 1

Name the component of the respiratory zone

Answer 1

Respiratory bronchioles, alveoli ducts, alveoli sacs, alveoli

Question 2

How far does gas have to travel for exchange?

Answer 2

0.5 micrometres

Question 3

The alveoli are in direct contact with what?

Answer 3

Capillary bed

Question 4

Describe the transition of the epithelium from terminal bronchioles to alveoli

Answer 4

In the terminal and respiratory bronchioles simple ciliated cuboidal interspersed with Club cells, then they transition into alveoli epithelium which consists of Type 1 pneumocytes (squamous epithelial cells), Type 2 pneumocytes (produce surfactant) and alveolar macrophages.

Question 5

Describe the function of club cells

Answer 5

Dome shaped secretory cells, can also act as stem cells to regenerate lower airways.
Secrete: lipoproteins (prevent luminal adhesion), anti-microbials.

Question 6

Describe the lung parenchyma

Answer 6

Elastic fibres surround throughout the bronchial tree and the alveoli- these are important to provide the elastic recoil of the lungs. Collagen is also present as a component of the inter alveolar septum.

Question 7

Describe pathologies involving elastic fibres and collagen

Answer 7

Compromised elastic fibres occurs in emphysema resulting in loss of elasticity and difficulty in expiration.
Up regulation of collagen is a characteristic feature of fibrotic lung disease.

Question 8

What produces the elastic and collage fibres

Answer 8

Fibroblasts within the inter alveolar septum

Question 9

Describe the inter alveolar septum

Answer 9

Two parts, the thin blood air barrier (type 1 pneumocyte directly against capillary) and the thick collagen part which provides a route for blood vessels and contains macrophages, fibroblasts and lymph vessels.

Question 10

Describe the two blood supply circuits to the lung

Answer 10

Pulmonary circulation- low pressure circuit carrying deoxygenated blood to the alveoli for oxygenation which then returns to the heart via pulmonary veins to the left atrium.
Bronchial circulation- high pressure circuit that supplies oxygenated blood to the to the tissues of the conducting zone.

Question 11

Where do the bronchial veins drain to?

Answer 11

The azygous vein

Question 12

What are the pressures in the pulmonary and systemic circuits?

Answer 12

Pulmonary artery- 25-35mmHg, vein 0-5mmHg

Bronchial artery- 80-120mmHg, vein 50-60mmHg