SFP: respiratory embryology Flashcards
What does the respiratory tract begin with?
Laryngotracheal groove
What happens after the development of the laryngotracheal groove?
There is a ventral evagination of endoderm to form lung buds
Describe the branching of lung buds.
It is asymmetrical; this gives 3 lobes in the right lung and 2 in the left.
What regulates the formation of lung buds?
EMT between gut endoderm and surrounding mesenchyme
What are the major signaling molecules in the formation of lung buds?
Retinoic acid made by the mesoderm upregulates TBX4 in the gut endoderm to initiate bud formation.
What weeks are the embryonic stage?
4-7
What happens in the embryonic stage?
Lung buds form and pleuropericardial folds begin to form.
What weeks are the pseudoglandular stage?
5-16
What happens in the pseudoglandular stage?
Lung buds form, but they resemble a gland more than anything else and respiration is not possible. There are no terminal or respiratory bronchioles.
What weeks are the canalicular stage?
17-26
What happens in the canalicular stage?
Respiratory bronchioles and alveolar ducts form. Respiration is possible at the end of this stage due to flattening of type I cells and surfactant secretion by type II.
What weeks are the terminal sac stage?
26-birth
What happens in the terminal sac stage?
More type I cells flatten, respiration is possible, and the lymph system develops.
When is the alveolar stage?
Birth-8 years
What happens in the alveolar stage?
The number of respiratory bronchioles grows.
The lung epithelium is derived from…
Endoderm
Glands are derived from…
Endoderm
Cartilage is derived from…
Splanchnic mesoderm
Lung connective tissue is derived from…
Splanchnic mesoderm
Muscle is derived from…
Splanchnic mesoderm
Blood and lymph vessels are derived from…
Splanchnic mesoderm
What separates the esophagus from the trachea?
Tracheoesophageal septum
What is a tracheoesophageal fistula?
A complication due to defect in the development of the tracheoesophageal septum.
What is the most common presentation of tracheoesophageal fistula?
Type C; Upper esophagus ends in a blind pouch and the lower segment forms a fistula with the trachea.
What is the most and least common form of TEF?
Most is type C, least is type E.
What factors are needed for normal lung development?
Adequate thoracic space, fetal breathing, and adequate amniotic fluid.
What causes lung hypoplasia?
Congenital diaphragmatic hernia, too little amniotic fluid (oligohydramnios).
What is the usual outcome of lung hypoplasia?
Death due to pulmonary insufficiency.
How are the lungs cleared of fluid?
Mouth and nose, pulmonary capillaries, lymphatics.
What is required for transition from depending on the placenta to autonomous gas exchange?
- Adequate surfactant
- Transformation of lungs from secretory to gas exchange
- Parallel pulmonary and systemic circulations.
What causes neonatal respiratory distress syndrome?
Insufficient surfactant production by type II cells.
What is the intraembryonic coelom?
Structure separating the two layers of lateral mesoderm. It is in a horseshoe shape in the cranial to caudal orientation.
What does the intraembryonic coelom form?
Pleural, pericardial, and peritoneal cavities.
What separates the pleural and pericardial cavities?
Pleuropericardial folds.
What forms the fibrous pericardium?
The expansion and fusing of pleuropericardial folds at the midline.
What is found between the heart and yolk sac?
A portion of somatic mesoderm from folding in the sagittal plane.
What are the 4 contributions of the diaphragm?
- Septum transversum develops in the central tendon
- Pleuroperitoneal folds fuse muscular ingrowth with central tendon
- Dorsal mesentery of esophagus
- Muscular ingrowth from lateral body wall.
Does a spinal cord injury below C3-5 impact the diaphragm?
No.
What is ectopic cordis?
Heart develops outside the body cavity due to failure of body wall closure in the thoracic region.
What is gastroschisis?
Failure of closure of the ventral body wall.
What causes a congenital diaphragmatic hernia?
Lack of fusion of pleuroperitoneal folds.
What causes eventration of the diaphragm?
Weakness of pleuroperitoneal membrane causes the intestines to push into the thoracic cavity.
