structure of the lower respiratory tract

Question 1

gas exchange figures

Answer 1

• 20m2 gas exchange area per lung
• Minute ventilation approx. 5 litres
• Cardiac output approx. 5 litres per minute
• Regional differences in ventilation and perfusion (blood supply)

Question 2

trachea

Answer 2

Larynx to carina (5th thoracic vertebra, T5)
• Oval in cross section
• Pseudo stratified, ciliated, columnar epithelium
• Goblet cells
• Semicircular cartilages
• Mobile (3cm and 1cm, superior and inferior)

Question 3

main bronchi

Answer 3

Left and right main bronchi
• Sharp division between these
• The carina
• R main bronchus more vertically disposed – 1-2.5cm long, related to the R pulmonary artery
• L main bronchus – 5cm long, related to the aortic arch

Question 4

lobar bronchi

Answer 4

Right – upper, middle and lower lobe

Left – upper lobe and lingular, lower lobe

Question 5

Acinus

Answer 5

• Distal to the terminal bronchiole
• Alveoli more profuse with increasing generation of subdivision
• Ducts are short tubes with multiple alveoli
• Interconnection between alveoli exist (pores of Kohn)

Question 6

Alveoli

Answer 6

• Type I pneumocytes Pavement
• Type II pneumocytes surfactant producers
• Alveolar macrophage
• Basement membrane
• Interstitial tissue
• Capillary endothelial cells

Question 7

lung innervation

Answer 7

Controls many aspects of function – smooth muscle tone, mucus gland secretion, vascular permeability, blood flow
• Sympathetic – bronchodilation
• Parasympathetic – bronchoconstriction
• NANC

Question 8

Pleura

Answer 8

2 main layers of mesodermal origin
• Visceral – applied to the lung surface
• Parietal wall– applied to the internal chest
• Each a single cell layer
• Small amount of fluid between
• Continuous with each other at lung root
• Parietal pleura has pain sensation
• Visceral pleura has only autonomic innervation

Question 9

blood supply

Answer 9

•	Bronchial and pulmonary circulations 
Pulmonary circulation 
•	L and R pulmonary arteries run from R ventricle
•	17 orders of branching 
•	Elastic (>1mm) and non elastic 
•	Muscular (<1mm)
•	Arterioles (<0.1mm)
•	Capillaries