Embryology of Respiratory Tract

Question 1

What body cavities does the IEC give rise to?

Answer 1

1. ONE pericardial cavity (houses heart)
2. ONE peritoneal cavity (at first there are 2!)
3. TWO pleural cavities (house the lungs)

Question 2

What are the pericardioperitoneal canals? What do they become?

Answer 2

a transient connection between the pericardial cavity and the peritoneal cavity (the pericardioperitoneal canals become the pleural cavities)

Question 3

What are the pleuropericardial membranes?

Answer 3

form across the IEC and separate the pleural cavities from the pericardial cavity

Question 4

What are the pleuroperitoneal membranes?

Answer 4

form across the IEC and separate the pleural cavities from the peritoneal

Question 5

What is the stomodeum? What tissue is it made out of?

Answer 5

ectodermally-lined pit! Formed around the OP membrane by bulges in the ectoderm (branchial arches) formed when neural crest cells migrate ventrally.

Question 6

What is Rathke’s pouch formed from and what will it become?

Answer 6

Rathke’s pouch is a diverticulum off the stomodeum; will become part of the pituitary

Question 7

What is the thyroid diverticulum formed from?

Answer 7

ENDODERM

Question 8

What is the thyroglossal duct? What is its fate?

Answer 8

The thyroid diverticulum forms off of the foregut and then forms the thyroglossal duct as it migrates downward. The thyroid gland forms at the bottom of the thyroglossal duct. This duct degenerates during development, leaving the thryoid gland below the thyroid cartilage.

Question 9

What can go wrong with the thyroglossal duct?

Answer 9

If the thyroglossal duct does not degenerate completely:

you can get residual cysts, or a fistula to the surface of the neck, aka thyroglossal sinus

Question 10

What is the laryngotracheal diverticulum?

Answer 10

the ENDODERMAL lung bud, which grows ventrally from the foregut

Question 11

What is the tracheoesophageal septum?

Answer 11

longitudinal folds separate the esophagus from the underlying tracheal tube, forming the tracheoesophageal septum between them

Question 12

What can go wrong with the formation of the tracheoesophageal septum?

Answer 12

if it deviates while forming, the esophagus may be blocked (atresia)

Question 13

What is a tracheoesophageal fistula?

Answer 13

If there is an esophageal atresia, then a second opening is likely to be created, to maintain patency of the esophagus.

Question 14

What is the purpose of surfactant?

Answer 14

Surfactant is a surface-acting lipid that decreases surface tension in alveoli

Question 15

What lines the primitive mouth?

Answer 15

Most of the gut is ENDODERM-lined but the stomodeum is ECTODERM-lined. So the mouth is differently lined in 2 regions.

Question 16

What tissues is the lung made up of? Why?

Answer 16

ENDODERM and MESODERM
The bronchial buds are endodermal and become surrounded by mesoderm as they grow. In the adult lung, the lower respiratory tract has endoderm origin and is wrapped by mesoderm.

Question 17

What are the 4 official stages of lung development?

Answer 17

1. pseudoglandular period
2. canalicular period
3. terminal sac period
4. alveolar period

Question 18

When, in general terms, is lung development complete?

Answer 18

terminal sac stage is the first stage where actual gas exchange could take place; efficient gas exchange takes place at the alveolar stage; lung development continues until the 8th year

Question 19

What is the major cause of respiratory distress syndrome and hyaline membrane disease in newborns?

Answer 19

insufficient surfactant (e.g. premature birth) leads to rapid labored breathing (alveoli cannot inflate properly); this sloughs off the lining and packs alveoli, which looks glassy under the microscope -> hyaline membrane disease

Question 20

Into what space do the 2 bronchial buds expand?

Answer 20

the pericardioperitoneal canals of the IEC