Question 1

A premature baby is not producing sufficient surfactant.What is known to stimulate surfactant synthesis prior to birth?

Accepted Answer

Thyroxine is known to stimulate surfactant synthesis in the fetal lungs prior to birth, helping to prepare the lungs for breathing air after delivery.

Question 2

A mouse exhibiting congenital diaphragmatic hernia was produced by ENU mutagenesis.What gene was mutated in this mouse?

Accepted Answer

Fog2 (Factor of Oocyte GENE 2) is known to be associated with congenital diaphragmatic hernia in humans, and Fog2-deficient mice exhibit similar symptoms. Therefore, the mutation in this mouse may have affected the Fog2 gene.

Question 3

A medical student is confused when learning that the muscle of the diaphragm is innervated by the phrenic nerves,based on the level of origin of these nerves from the CNS.What is the explanation of how this innervation occurs during embryogenesis?

Accepted Answer

The phrenic nerves arise in the cervical region in association with the septum transversum and cervical myotomes during embryonic development. As the myotomes migrate more caudally to form the diaphragm, they carry their innervation with them, resulting in the diaphragm being innervated by the phrenic nerves, despite arising from thoracic myotomes.

Question 4

Branching of the Drosophila tracheal system involves three genes,Branchless,Breathless,and Sprouty,and orthologs of these genes play similar roles in vertebrate lung development.What would be the expected outcome if Sprouty is inactivated during Drosophila development?

Accepted Answer

Sprouty acts as an inhibitor of the FGF (Fibroblast Growth Factor) signaling pathway, which is involved in the branching of the tracheal system. Inactivating Sprouty would remove this inhibition, leading to increased FGF signaling and consequently extra branching of the tracheal system.

Question 5

In tissue recombination experiments in culture it has been shown that branching morphogenesis of the lung involves epithelial-mesenchymal interactions.What is the source of the lung epithelium?

Accepted Answer

The lung epithelium is derived from the endoderm during embryonic development.

Question 6

A premature baby,born at 30 weeks,is suffering from respiratory distress.What stage of lung development would the lungs have reached at the time of delivery?

Accepted Answer

At 30 weeks of gestation, the lungs are in the saccular stage of development, which occurs from approximately 26 weeks to birth. This stage is characterized by the formation of terminal sacs (primitive alveoli) and the beginning of surfactant production, which is crucial for reducing surface tension in the lungs and aiding in breathing.

Question 7

An embryologist is studying the development of the phrenic nerve in human embryos.He reads that these nerves course through tissues involved in coelom partitioning.What is this tissue?

Accepted Answer

The tissues involved in coelom partitioning include the pleuroperitoneal membrane, pleuropericardial fold, septum transversum, and dorsal mesentery. However, since the question specifically mentions the phrenic nerve, which runs through the tissues that form the diaphragm, the best choices would be the pleuropericardial fold and the septum transversum.

Question 8

A baby with a severe diaphragmatic hernia with herniation of visceral into the pleural cavity also has other anomalies of the respiratory system.What anomaly is likely to be present?

Accepted Answer

A diaphragmatic hernia can cause compression of the developing lungs, leading to pulmonary hypoplasia. This is a common finding in infants with this condition. The other anomalies listed do not typically occur in conjunction with a diaphragmatic hernia.

Question 9

Transgenic and gene targeting approaches have played important roles in understanding lung development and branching morphogenesis.Using this approach,Fgf signaling was blocked in the developing respiratory tree.What was the outcome of this experiment?

Accepted Answer

Blocking Fgf signaling in the developing respiratory tree would result in the failure of branching morphogenesis, which is a critical process for the proper formation of the lung structure. This would lead to the lungs not developing properly and potentially causing respiratory problems or even death. Tracheoesophageal fistula or esophageal atresia are not directly related to Fgf signaling, and cystic fibrosis is a genetic disorder that is not caused by blocking Fgf signaling.

Question 10

Pulmonary hypoplasia is often associated with which prenatal condition?

Accepted Answer

Pulmonary hypoplasia is often associated with oligohydramnios, which is a condition where there is a low level of amniotic fluid in the uterus. This can result in underdevelopment of the lungs in the developing fetus, leading to pulmonary hypoplasia. Polyhydramnios, on the other hand, is a condition where there is an excess level of amniotic fluid in the uterus and is not typically associated with pulmonary hypoplasia.

Quiz 12: Development of the Respiratory System and Body Cavities