Thorax, tracheobronchial tree and lungs

Question 1

What spinal levels does the phrenic nerve derive from?

Answer 1

C3, 4, 5

Question 2

How does the respiratory system develop embryologically?

What does the mesoderm form?

Answer 2

• The respiratory diverticulum begins to grow out of the gut tube at around 4 weeks gestation.
• Lung (bronchial) buds grow out of the inferior aspect of the respiratory diverticulum.
• Buds grow into splanchno-pleuric mesoderm at around week 5.
  
  • Mesoderm forms blood vessels, cartilage, smooth muscle and visceral pleura
• Tracheo-oesophageal septum forms and the developing trachea separates from the gut tube (around week 4-5)

Question 3

What embryological malformations can be formed from the developing embryonic lungs?

Answer 3

• Proximal atresia with distal fistula:
  
  • ​Blind-ended oesophagus
  • Distal oesophagus forms fistula with trachea.
• Fistula
  
  • ​Both proximal and distal oesophagus form fistula with trachea

Both caused by failure of septation of the trachea and gut tube.

Question 4

How do the bronchial buds branch?

What is the significance of week 26 in the development of the lungs?

Answer 4

Right lung bud branches into 3 secondary buds

Left lung bud branches into 2 secondary buds.

Segmental bronchi develop around 56 days

By week 16 all major lung parts have developed except those needed for gas exchange.

Respiratory epithelia (lining of terminal bronchioles and alveolar sacs) develops at around week 26 (hence why babies born premature to 26 weeks have very low chance of survival)

Question 5

Label the lobes and fissures on the lungs

Answer 5

Question 6

What do the medial surfaces of both lungs contain?

Label the structures on the diagram

Answer 6

Hilum

Question 7

Where is the point of the pleural reflection?

Answer 7

At the hilum of the lungs

Question 8

What type of blood do the pulmonary arteries carry?

What type of blood do the pulmonary veins carry?

Answer 8

Pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs

Pulmonary veins carry oxygenated blood from the lungs to the left atrium

Question 9

Label the structures on the diagram

Where does the phrenic nerve pass in relation to the hilum?

Which nerve passes posterior to the hilum?

Answer 9

Phrenic nerve passes anterior to the hilum

Vagus nerve passes posterior to the hilum

Question 10

Label the vessels on the diagram

Answer 10

Question 11

What do the lungs act as a filter for?

How can these enter the lungs?

Answer 11

Lungs can filter venous thromboses; these can be carried to the lungs via the pulmonary arteries.

Question 12

Where do the right and left recurrent laryngeal nerves branch off the vagus nerve?

Answer 12

• Right recurrent laryngeal nerve:
  
  • Occurs at right lung apex under right subclavian artery
  • Hoarseness of voice can indicate compression/damage to recurrent laryngeal nerve- if on right side could be from apical lung tumour.
• Left recurrent laryngeal nerve:
  
  • Occurs at lung hilum/aortic arch
  • Can be compressed by aortic aneurysm

Question 13

What do the lung pleura line?

How are the two pleura held together?

Answer 13

Visceral: line the lung tissues

Parietal: lines inside of thoracic cavity

Pleural layers are held together by surface tension

Question 14

Define:

Pneumothorax

Haemothorax

Chylothorax

Effusion

Tension pneumothorax

Answer 14

• Pneumothorax: air in the pleural space
• Haemothorax: blood in the pleural space
• Chylothorax: lymph fluid in pleural space
• Effusion: fluid leaking out of lung into pleural cavity
• Tension pneumothorax: each time the patient breathes in, more air enters the pleural space but none escapes.
  
  • Medical emergency: pleural cavity can continue to expand and compress heart.

Question 15

What can be seen on x-ray in a patient with a tension pneumothorax?

How would this be treated?

Answer 15

Tension pneumothorax:

• Mediastinal shift
• Tracheal deviation
• Diaphragmatic depression
• Increased intercostal space size
• Hyper-resonance
• Unilateral hyper-inflation

Needle decompression in 2nd intercostal space in mid-clavicular line.

Question 16

What are the surface markings of the lung?

Answer 16

• Apex: around 2cm superior to the medial 3rd of clavicle
• Tracheal bifurcation: just below sternal plane or at T4/5 (approx 2nd costal cartilage)
• Border of middle/inferior lobe: 6th costal cartilage in MCL.
• Lower border of lung in normal breathing: 6th cc, 6th rib mid-clavicular line and 8th rib in mid axillary line.
• Oblique fissue: T3 spinous process to 6th costal cartilage anteriorly.
• Horizontal fissure: 4th costal cartilage horizontally back to oblique fissure
• Lower border of pleural reflection: 6th cc, 8th rib MCL, 10th rib MAL.

Question 17

Where are the auscultation points of the lung?

Answer 17

Superior lobe: auscultate anteriorly

Middle lobe: Mid axillary line

Inferior lobe: Posteriorly, below oblique fissure (roughly marked by abducted scapula, T3 to 6th cc anteriorly)

Question 18

What does the medial border of an abducted scapula roughly mark the location of?

Answer 18

Oblique fissure

Question 19

During normal breathing, what paravertebral level approximately marks the lower border of the lung?

What paravertebral level marks the lower border of the lung at end tidal inspiration?

Answer 19

Normal breathing: T10 paravertebral level

End tidal inspiration: T12 paravertebral level

Question 20

Where is the costodiaphragmatic recess found?

What is it? What is its clinical relevance?

Answer 20

Between T10 and T12 paravertebral levels, lies between the thoracic wall and diaphragm.

Region between lung and the pleural reflection.

Lung expands into the costodiaphragmatic recess during deep inspiration. It can also be a location for fluid collection in pleural effusion.

Question 21

What are the anatomical relations of the costodiaphragmatic recess?

What vertebral levels are they at?

Answer 21

Kidneys

Liver

Spleen

Question 22

Where is the triangle of safety for chest drain insertion?

What could be damaged by insertion of a chest drain posterior to the triangle of safety?

Answer 22

• Posterior border: Mid axillary line
• Inferior border: 5th rib
• Anterior border: posterior border of pectoralis major (anterior axillary fold)
• Roof: base of axilla
• Drain should be inserted within this triangle in the 4th intercostal space.

Insertion of a chest drain posterior to the triangle of safety could damage the long thoracic nerve causing loss of innervation to the serratus anterior (patient cannot raise arm above 90°)

Question 23

Where can the trachea be palpated?

At what vertebral levels does it bifurcate and enter the hilum of the lungs?

What is located at the bifurcation? What should it look like on endoscopy?

Answer 23

Above the sternal notch

Bifurcates at T4/5

Enters the hilum of the lungs at T5/6

The carina is located at the bifurcation, should appear thin and pointed. Widens due to lymph node swelling beneath.

Question 24

What is the significance of the right bronchus being wider than the left?

Answer 24

Aspirated food/liquid is more likely to enter the right bronchus (path of least resistance)

Question 25

Describe the divisions of the tracheobronchial tree

Label them on the diagram

Answer 25

Trachea divides into right and left main bronchi.

Main bronchi divide into lobar branches

Lobar branches divide into segmental branches

Question 26

Describe bronchopulmonary segments

What can affect their drainage?

Answer 26

Smallest functionally independent sections of the lung, pyramid shaped.

Each segment has its own blood and air supply; air supplied by tertiary bronchi.

Apex of each segment is directed towards the hilum of the lung

Normally 10 in right lung and 8-9 in left lung

Gravity and posture can affect their drainage; in a supine patient fluid can collect in segment VI.

Question 27

What are the walls of the bronchi and bronchioles made up of?

Answer 27

Bronchi: cartilage, smooth muscle and elastic fibres

Bronchioles: smooth muscle, elastic fibres

Question 28

Where do branches of the pulmonary artery and vein run?

What do the bronchial arteries supply? Where do they branch from?

Answer 28

Branches of the pulmonary artery run with the bronchial tree

Branches of the pulmonary vein run between segments.

Bronchial arteries arise from the descending aorta and supply the bronchi and lung connective tissue.

Question 29

Describe the lymphatic drainage of the lungs

Name the lymph nodes found throughout the lungs

Answer 29

Drainage follows the tracheobronchial tree:

Hilar/bronchial pulmonary nodes → tracheobronchial nodes → paratracheal nodes → bronchomediastinal duct →

• The right lymphatic duct drains all lymphatic fluid from the lungs except the left upper lobe; drains it into the right subclavian vein.
• Left upper lobe is drained by the thoracic duct into the left subclavian vein.