The Structure Of The Lower Respiratory Tract

Question 1

Main functions

Answer 1

Gas exchange

-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

Location: Larynx to carina (5th thoracic vertebra, T5)

Oval in cross section
Pseudo stratified, ciliated, columnar epithelium
Goblet cells
Semicircular cartilages
Mobile (3 cm and 1cm, superior and inferior)

Heads into superior mediasternum
Carina sternal angle level
Sensory innervation recurrent

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 (more angulated and longer)
-5cm long, related to the aortic arch

Question 4

Lobar bronchi

Answer 4

Right
-upper lobe
-middle lobe
-lower lobe

Left
-upper lobe and lingualar
-lower lobe

Question 5

Lower respiratory structure

Answer 5

Terminal and respiratory bronchioles are distinguished by the fact that respiratory bronchioles have discernible (visible) alveoli protruding from them

Question 6

Acinus

Answer 6

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 7

Alveoli

Answer 7

Type I pneumocytes- Pavement

Type II pneumocytes- Surfactant producers

Alveolar macrophage

Basement membrane

Interstitial tissue

Capillary endothelial cells

Question 8

Pleura

Answer 8

2 main layers, of mesodermal origin

Visceral- Applied to the lung surface
Parietal- Applied to the internal chest wall

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