Embryology ✅ Flashcards
Where does the respiratory tree arise from?
The ventral surface of the foregut
What are the phases of lung development?
- Embryonic phase
- Pseudoglandular phase
- Canalicular phase
- Saccular phase
- Term
When does the embryonic phase of lung development occur?
3-5 weeks
What happens in the embryonic phase of lung development?
The respiratory bud arises from the ventral surface of the foregut
What kind of mesoderm does the respiratory bud arise from?
Splanchnic
When does the pseudoglandular phase of lung development occur?
6-16 weeks
What is formed in the pseudoglandular phase?
Bronchial tree
What develops in parallel to the bronchial tree during the pseudoglandular phase?
The arterial supply to each lung
What is the result of the arterial supply of each lung arising parallel to the bronchial tree?
Arteries are found alongside each airway, a pattern that persists into adulthood
When do the pulmonary veins develop?
At a similar time to the arteries and bronchial tree
Do the pulmonary veins accompany the airways?
No
Where do the pulmonary veins lie?
In the intersegmental plane
When is smooth muscle present in the trachea and bronchi from?
10 weeks
When does cartilage develop in the respiratory system?
6 weeks
When are ciliated cells seen?
12 weeks onwards
When is the canalicular phase of respiratory development?
17-24 weeks
What happens in the canalicular phase of lung development?
- Distal airways develop
- Epithelial cells subdivide into type I pneumocytes and type II pneumocytes
What is the purpose of type I pneumocytes?
Gas exchange
What is the purpose of type II pneumocytes?
Surfactant production
When is the saccular phase of lung development?
24 weeks - term
What happens in the saccular phase of lung development?
Terminal sacs, alveolar ducts, and finally alveoli form, increasing surfactant production from 24 weeks
How to the lungs of a term neonate compare to adults?
They have 1/5 of the number of alveoli
What happens to alveoli during childhood?
Alveolar multiplication and maturation continues into early childhood
What can abnormal embryological development of the lungs lead to?
Congenital thoracic malformations (CTMs)
Give 7 examples of abnormal embryological development of the lungs?
- Failure of complete separation of the foregut and bronchial structures
- Congenital pulmonary airway malformations
- Pulmonary sequestration from abnormal blood supply to part of the lung
- Congenital diaphragmatic hernia
- Cysts
- Congenital lobar emphysema
- Lung agenesis/bronchial atresia
What does failure of separation of the foregut and bronchial structures lead to?
Different types of tracheo-oesophageal fistula
What causes congenital pulmonary airway malformations?
Abnormal development of alveolar or bronchial tissues
Is pulmonary sequestration from an abnormal blood supply to part of the lung systemic or pulmonary?
Usually systemic
What causes congenital diaphragmatic hernia?
Maldevelopment of the pleuroperitoneal canal
What are the types of cysts that can arise due to abnormal embryological development of the lungs?
- Bronchogenic
- Foregut
What causes congenital lobar emphysema?
Partial obstruction of the developing airway
What is the most common cause of partial obstruction of the developing airway leading to congenital emphysema?
Deficiency of bronchial cartilage development
What causes lung agenesis/bronchial atresia?
Maldevelopment of the bronchial tree in early fetal life
