TBL 10: Development of Lungs Flashcards
From what embryological layer is epithelium of the trachea and its descendent airways derived from?
The epithelium of the trachea and its descendent airways is derived from endoderm.
From what mesoderm is connective tissue, cartilage, and smooth muscle of the airways derived from?
Connective tissue, cartilage, and smooth muscle of the airways are derived from mesenchymal cells of the visceral mesoderm.
What does the tracheo-esophageal septum divide?
While the lung bud expands caudally, the tracheo-esophageal septum divides the distal foregut into posterior and anterior portions occupied by the esophagus and trachea, respectively.
What is the most common type of tracheoesophageal fistula and why can it be associated with polyhydramnios and pneumonia?
The most common type of tracheoesophageal fistula (90%) results in the upper portion of the esophagus ending in a blind pouch and the lower segment forming a fistula with the trachea.
This is associated with polyhydramnios (excessive accumulation of amniotic fluid) because the fetus cannot pass swallowed amniotic fluid to the stomach and intestines.
This is associated with pneumonia because gastric contents and/or amniotic fluid at birth may enter the trachea through a fistula.
As the lung buds progressively branch, differentiation of the lobar and segmental bronchi occurs. What is associated with the differentiation of bronchioles at distal ends of the segmental bronchi?
Differentiation of bronchioles at distal ends of the segmental bronchi is associated with angiogenic proliferation of pulmonary capillaries from the segmental pulmonary arteries.
What forms the alveolar sacs?
What is located in close proximity to the lining of these sacs and what type of tissue is this lining made of?
The clustering of the pulmonary alveoli forms the alveolar sacs.
Pulmonary capillary endothelium is placed in close opposition to the lining of the alveoli which is made of simple squamous epithelium.
How is fetal breathing movements and consequent aspiration of amniotic fluid important to fetal respiratory development?
How does fluid removal from the lungs coincide with the onset of neonatal respiration?
Fetal breathing movements are important for stimulating lung development and conditioning respiratory muscles.
When respiration begins at birth, most of the lung fluid is rapidly resorbed by the blood and lymph capillaries, and a small amount is probably expelled via the trachea and bronchi during delivery. When the fluid is resorbed from alveolar sacs, fatty surfactant remains deposited as a thin phospholipid coat on alveolar cell membranes. This surfactant layer is vital for reducing the surface tension on the outside of the alveolar sacs and preventing their collapse during expiration.
