The structure of the Lower Respiratory Tract

Question 1

What is the main function of the lungs?

Answer 1

Gas exchange

Question 2

What is the gas exchange area per lung?

Answer 2

20m^2

Question 3

What is the minute volume?

Answer 3

approx 5 litres (the volume of air inhaled/exhaled a min)

Question 4

What is the cardiac output?

Answer 4

approx 5 litres per min (volume of blood pumped out by the heart a min)

Question 5

Where does the trachea run from & to?

Answer 5

From larynx to carina (C6 - T5)

Question 6

Describe the structure of the Trachea

Answer 6

Oval in cross section

Semicircular hyaline cartilages (C-Shaped cartilage increases flexibility of trachea)

Pseudo-stratified ciliated columnar epithelium

Has goblet cells

Question 7

What is the difference between the upper and distal trachea?

Answer 7

upper is more mobile than distal

Question 8

What does the main bronchi consist of & and where is the sharp division?

Answer 8

The left & right bronchus and sharp division at the carina (T5)

Question 9

Which bronchus is more vertically disposed, by how much and what does this mean?

Answer 9

Right main bronchus is more vertically disposed (more risk of getting things trapped=choking)
1-2.5cm long, related to the right pulmonary artery

Question 10

Describe the position of the left main bronchus

Answer 10

comes off at more an angle, 5cm long, related to the aortic arch

Question 11

Where are things more likely to get stuck & why?

Answer 11

More likely to get stuck in the right main bronchus as it is more vertically disposed & the left main bronchus is longer & more angled than the right

Question 12

What comes after the left & right main bronchus?

Answer 12

The lobar bronchi

Question 13

How many divisions do the left & right lobar bronchi have & what are the different segment?

Answer 13

Right - 3 divisions, upper lobe, middle lobe, lower lobe

Left - 2 divisions, upper lobe, lower lobe

Question 14

What comes after the lobar bronchi?

Answer 14

The segmental branches/bronchi

Question 15

How many branches does the segmental bronchi have (left & right)?

Answer 15

Right - 10

Left - 8

Question 16

What comes after the segmental bronchi?

Answer 16

Terminal bronchioles, respiratory bronchioles, alveolar ducts, alveoli

Question 17

What is the acinus?

Answer 17

The tissue supplied with air by one terminal bronchiole

Question 18

Describe the alveoli (cell types)?

Answer 18

Type l pneumocytes
Type II pneumocytes - secrete surfactant 
Alveolar macrophages 
Membrane 1 micron thick 
Columnar ciliated epithelium 
Basement membrane

Question 19

Where are the nerves of the lungs derived from?

Answer 19

The pulmonary plexus which lies behind each hilum

Question 20

What does the pulmonary plexus/lung receive innervation from?

Answer 20

Left and right vagus nerve (CNX) and T2-T4 ganglia of the sympathetic trunk

Question 21

Where specifically does innervation come from and what does it result in?

Answer 21

Sympathetic NS (sympathetic trunk) - results in bronchodilation (relaxation of bronchial smooth muscle)

Parasympathetic NS (vagus nerve) - bronchoconstriction

Visceral afferent - conduct pain impulses to sensory ganglion of vagus nerve

Question 22

Which lung is larger and why?

Answer 22

Right due to silhouette of heart

Question 23

Describe the structure of the lungs

Answer 23

Right lung has 3 lobes - superior, middle, inferior

Left has 2 lobes - superior, inferior

Question 24

How many layers are there of the lung pleura, their names, where they’re applied to and nerves

Answer 24

2 layers of mesodermal origin
Visceral- applied to lung surface- only has autonomic innervation
Parietal- applied to internal chest- pain sensation via phrenic
Each is a single layer of cells

Alveoli, visceral, intra pleural space (pleural fluid), parietal