Structure and Function of the Airways

Question 1

Why are tracheal cartilage rings C shaped

Answer 1

To make space for the oesophagus, efficient swallowing without running up against rings

Question 2

What are type 1 and type 2 alveolar cells

Answer 2

Type 1 are thin and delicate,

type 2 cells are chubby and replicate to replace type 1 cells, secrete surfactant, anti protease, xenobiotic metabolism (noxious particles)

Question 3

What is the function of nasal conchae

Answer 3

Very vascular; warming and humidification of intra-nasally-inhaled air, nasal hairs filter out large particles

Question 4

How do ciliated cells waft mucus

Answer 4

Microtubules beat in a metachronal fashion, move backwards and forward in time to move mucus

Question 5

What inflammatory and regulatory mediators are produced by airway epithelium

Answer 5

Nitric oxide via nitric oxide synthase
Carbon monoxide via hemeoxygenase
Arachiodonic acid metabolites, eg prostaglandins via COX
Chemokines eg IL-8
Cytokines eg GM-CSF
Pro teases

Question 6

What are the functions of air way smooth muscle

Answer 6

Structure
Tone (airway caliber, contraction and relaxation)
Secretion (mediators, cytokines, chemokines)

Question 7

What condition may cause smooth muscle hypertrophy in the airways

Answer 7

Asthma

Question 8

What happens to airway smooth muscle in respiratory disease

Answer 8

Inflammation causes
Hypertrophy and proliferation
Excessive Secretion of mediators, cytokines and chemokines, prostaglandins, NO, adhesion molecules
Lead to inflammatory cell recruitment

Question 9

Describe the cardiac output vs the blood flow to in tracheo-bronchial circulation

Answer 9

1-5% cardiac

100-150mL/min/100g tissue (amongst highest to any tissue

Question 10

Where does arteries and veins in the tracheal-bronchial circulation arise and return to the heart from

What does this achieve

Answer 10

Bronchial arteries arise from many sites on aorta, intercostal arteries etc
Blood returns from tracheal circulation via systemic veins, returns from bronchial circulation via bronchial and pulmonary veins

Massive perfusion of blood

Question 11

Why is the subepithelium micro vascular network so abundant

Answer 11

Good gas exchange directly between airway tissues and blood
Warming and humidification of inspired air
Clears inhaled drugs
Supplies airway tissue and lumen with inflam cells, and proteinaceous plasma (plasma education)

Question 12

How is contraction and relaxation of the airways controlled

Eg a peanut blocking airways

Answer 12

Detected by sensory nerves, go through vagus, through Nodose ganglion, into brainstem
Sets off cholinergic motor pathway (parasymp)
Causes CONTRACTION (Prevents peanut going down further)
Coughed up
Adrenaline produced, RELAXATION
Nerves containing nitric oxide synthase, release NO which causes relaxation

Question 13

What respiratory disease are characterised by a loss of airway control

Answer 13

Asthma, chronic obstructive pulmonary disease (COPD), Cystic Fibrosis (CF)