Thorax, Tracheobronchial Tree & Lungs (Part 2) Flashcards
What is the mediastinum?
Central region bounded by the pleural cavities surrounded by lungs & just below the manubrium/sternal angle
How does the respiratory system develop?
- Respiratory diverticulum appears as an outgrowth of the gut tube; oesophagus separates from trachea via septum (4 weeks)
- Lung/bronchials then bud off of this
- Buds grow into splancho-pleuric mesoderm (week 5)
- Mesoderm forms blood vessels, cartilage, SM & visceral pleura
- Endoderm forms lining & glands
What 2 embryological things can go wrong in the development of the respiratory tract?
Issues separating trachea & oesophagus:
- Proximal atresia w/distal fistula: blind ended oesophagus at top and trachea-oesophageal link inferior to it
- Fistula: oesophagus goes into trachea & off of it again i.e. they have not separated properly
How do lung/bronchial buds branch embryologically?
Day 28: trachea branches into bronchial buds
Day 35: R and L secondary bronchus branch
Day 56: segmental bronchi develop (mesoderm divides with them too)
Week 16: all major lung parts developed
Week 26: respiratory epithelia begins to develop
7-10 years: full lung maturation
Why do babies who are born before 26 weeks have a much higher mortality rate?
Respiratory epithelia has not developed fully as this stage & therefore gaseous exchange cannot happen so the baby cannot breath (not much you can do as a doctor to speed up the development of this)
Describe the structure of the lungs.
R lung: 3 lobes (superior, inferior; middle); 2 fissures (oblique & horizontal) - 10 segments
L lung: 2 lobes (superior & inferior); 1 fissure (oblique) - 8-9 segments
ALTHOUGH this can vary
Why is the separation of lungs via lobes a good characteristic?
Disease, collapse or atelectasis can affect lobes independently
What are the anatomical relations of the lungs?
Rib 1
Diaphragm (& liver on R)
Oesophagus
Cardiac impression (L)
Veins: azygous, SVC & IVC (R) and brachiocephalic (both)
Arteries: subclavian, descending aorta & aortic arch (L)
What does the mediastinal surface of both lungs contain?
The hilum i.e. where all structures going to & from the lungs pass
What structures make up the hilum of the lungs?
Blood, vessels, nerves, lymphatics & airways:
Pulmonary artery
Pulmonary veins
Autonomic nerves
Main/lobar bronchi
Point of pleural reflection (parietal & visceral pleura) Pulmonary ligament (fold of parietal pleura)
Phrenic nerve passes anterior
What do the pulmonary vessels do?
2 pulmonary arteries (R & L) carry deoxygenated blood from heart to each lung
4 pulmonary veins (L & R superior + inferior) carry oxygenated blood from lungs to LA of heart
How can venous thromboses pass into the lungs?
Via pulmonary artery where it is then taken to the lungs (good at catching clots before they get to heart/brain)
What important nearby structures can be damaged by lung pathology? Whereabouts are they?
Vagus nerves: posterior to hilum & branches off into RLNs ->
R RLN: recurs at R lung apex under R subclavian artery)
L RLN: recurs at hilum/aortic arch)
Phrenic nerve: anterior to hilum
Describe the pleural layers of the lungs.
Visceral & parietal pleura surround lungs & held closely together via surface tension - potential space containing serous fluid between them called pleural cavity
Visceral covers lung surface into fissures & reflected at hilum as parietal pleura
Parietal pleura lines pleural cavity walls; costal, mediastinum, cervical & diaphragm
What are the different ways in which you can disturb the surface tension of the pleural cavity?
Pneumothorax Tension pneumothorax Haemothorax Chylothorax Pleural effusion
What is a tension pneumothorax?
Occurs when pressure of air trapped in the pleural cavity continues to increase
What will show on a chest X-ray if a patient has a tension pneumothorax?
Mediastinal shift Tracheal deviation Diaphragmatic depression Unilateral hyperinflation Increased intercostal space size Hyper-resonant
What do you do if a patient has a tension pneumothorax?
Needle decompression: stick needle into 2nd intercostal space at midclavicular line to relieve air