Lung Embryology Flashcards
The epithelium and glands of the larynx, trachea and bronchi, as well as the epithelium from the lungs arise from which embryological tissue?
endoderm
What embryological structure gives rise to the laryngotracheal groove?
Ventral wall of primitive pharynx (caudal to 4th pharyngeal pouch)
What are the surrounding tissues to the lung (smooth muscle, cartilage, connective tissue) derived from?
splanchnic mesenchyme
What is the laryngeal cartilage developed from?
Neural crest mesenchyme
Describe the trajectory of the developing structure that separates the esophagus from the trachea.
Tracheoesophageal fold -> Tracheoesophageal septum -> Esophagus and laryngotracheal tube
Which levels of pharyngeal arches give rise to the laryngeal cartilage?
4th and 6th
What did the fourth and sixth pharyngeal arches develop from?
Neural crest mesenchyme
What are the laryngeal muscles developed from?
Myoblasts from 4th and 6th pharyngeal arches
What innervates laryngeal muscles?
Vagus nerve: Superior laryngeal and recurrent laryngeal nerves
What is the most common congenital abnormality of the lower respiratory tract?
Tracheoesophageal fistula
What is the most common tracheoesophageal fistula structure?
Esophageal atresia with caudal fistula
What complications arise from an esophageal atresia with caudal fistula?
Inability to swallow into stomach
Lipid pneumonia in lungs
Digestive enzymes in lungs
What developmental abnormality results in a tracheoesophageal fistula?
Abnormal partitioning of tracheoesophageal septum
Why is polyhydramnios seen in TE fistulas?
Accumulation of amniotic fluid because fetus cannot swallow and digest amniotic fluid, resulting in less transfer to mother’s blood through the placenta
Outline the structural development of the bronchopulmonary segments from the laryngotracheal groove
Laryngotracheal groove -> laryngotracheal diverticulum -> respiratory bud -> primary bronchial buds -> secondary bronchial buds -> segmental branches (bronchopulmonary segments)
What embryological structure do the bronchial buds grow into?
Pericardioperitoneal canal
What is bronchial connective tissue, smooth muscle, cartilagenous plates, pulmonary connective tissue and vasculature derived from?
Splanchnic mesoderm
What is the visceral pleura derived from?
Splanchnic mesoderm
What is the parietal pleura derived from?
Somatic mesoderm
What is an azygous lobe?
When part of the lung bud grows medial to the azygous vein instead of lateral, leading to an indentation of the lung and giving another pseudolobe
What abnormal muscular development oftentimes results in lung hypoplasia?
congenital diaphragmatic hernia
What is the developmental abnormality with congenital diaphragmatic hernias?
Pleural peritoneal membrane fails to fuse with developing diaphragm
How does oligohydramnios cause lung hypoplasia?
Uterus presses down on thorax, compresses lung development
The part of lung development where ductal airways start to form but alveoli are not present is called…
Pseudoglandular stage
What direction do respiratory passageways start to form?
Cranial to caudal
What stage of lung development is characterized by vascularization of developing alveoli?
Canalicular stage
During which stage of development do pneumocytes start to form?
Saccular stage
What do type 1 pneumocytes arise from?
Endoderm
What is the type I pneumocyte? Type II pneumocyte?
Type I pneumocyte: simple squamous epithelium of endodermal origin
Type II: Glandular cell that makes surfactant
What two specific things are the most significant determinants of neonatal survival?
Adequate vasculature and surfactant
What two cells basement membranes fuse during development?
Type I Pneumocytes and capillary epithelial cells
What do respiratory movements do for the fetus?
Develop musculature
What results in the removal of alveolar fluid from the thorax?
- Pressure on thorax during vaginal delivery, out of nose and mouth
- Into capillaries
- Into lymph
What results in hyaline membrane disease/Respiratory distress syndrome?
Inadequate surfactant production
Administration of what during development results in more rapid lung development?
Corticosteroids (betamethasone)
What weeks of development is the fetus in the pseudoglandular stage?
6-16 weeks
What stage of development is the fetus in the canalicular stage?
16-26 weeks
At what stage of development is the fetus in the saccular stage?
26 weeks-birth
