Airway and Body Development

Question 1

What is the embyronic mouth opening called?

Answer 1

Stomodeum

Question 2

What becomes the nasal conchae?

Answer 2

Buccopharyngeal membrane

Question 3

What is the embryonic structure that becomes the larger airways called?

Answer 3

Respiratory diverticulum, off the gut tube.

Question 4

What separates the respiratory diverticulum from the foregut?

Answer 4

Tracheoesophageal ridges.

Question 5

What is the embryonic origin of the esophagus?

Answer 5

Foregut

Question 6

What does the respiratory diverticulum extend from in the embryonic larynx?

Answer 6

Laryngeal orifice, found between the laryngeal swellings inferiorly and the epigottal swelling superiorly.

Question 7

What forms the false vocal folds and ventricles?

Answer 7

The epithelium at the base of the tongue overgrows to close the laryngeal orifice, but it is later re-canalized.

Question 8

What is the most common congenital anomaly of the upper airway?

Answer 8

Laryngomalacia, or floppiness of the larynx.

Question 9

What is laryngomalacia? Characteristics?

Answer 9

The most common congenital anomaly of the upper airway.

It presents with inspiratory stridor in the first week weeks of life, worse in supine position, and peaks at 6 months of age, resolving around 18-24 months.

Severe cases involve aspiration or laryngeal closure while sleeping usually.

Question 10

What is subglottic stenosis?

Answer 10

3rd most common congenital laryngeal anomaly.

Incomplete re-canalization of the laryngeal tracheal tube during 3rd month of gestation. Forms laryngeal webs, which we can excise endoscopically, but severe ones require tracheotomy and laryngeal reconstruction.

Question 11

What is tracheoesophageal fistula?

Answer 11

Abnormal connection between trachea and esophagus. Most of the times, the upper esophagus ends in a blind pouch, while the lower segments originates from above the tracheal bifurcation.

Note: Always has associated tracheomalacia.

Question 12

What is a laryngeal cleft?

Answer 12

It is a slit-like opening between the posterior larynx and esophagus.

Presents with recurrent aspiration and cyanosis while feeding.

Caused by failure of the primitive tracheoesophageal septum.

AKA your breathing and eating tubes are connected.

Question 13

What happens during weeks 5-26 for the respiratory diverticulum?

Answer 13

It enters the mesoderm, branches, and associates with blood vessels.

Question 14

What happens during weeks 27-birth for the respiratory diverticulum?

Answer 14

Epithelial cells flatten and from blind sacs in much closer contact with vessels.

Question 15

What happens from birth-10 years of age for the respiratory diverticulum?

Answer 15

Branching becomes finer, cells flatten to increase surface area.

Takes 10 years for your airways to reach peak complexity!

Question 16

What pneumocytes start appearing during our terminal sac period?

Answer 16

Type I, meaning we can have gas exchange. AKA a fetus can’t survive until late stages of pregnancy because they won’t have functional lungs.

Question 17

When do we start secreting surfactant?

Answer 17

6 months of gestation.

Question 18

How much of our alveolar pneumocytes are present when we are born?

Answer 18

16%, takes 10 years to develop all of them!

Question 19

What gives us our initial surfactant after birth?

Answer 19

Amniotic fluid. Insufficient amounts will cause atelecstasis, resulting in respiratory distress syndrome.

Question 20

What two parts of development does breathing rely on?

Answer 20

Proper lung development + Body wall development

Question 21

What is the lateral plate mesoderm separated into and by what?

Answer 21

Separated into the somatic layer and visceral layer by intraembryonic coelem.

Somatic layer = somatic mesoderm + ectoderm
Visceral layer = visceral mesoderm + endoderm.

Question 22

What two layers fold to form the gut tube and mesentery?

Answer 22

Visceral mesoderm and endoderm.

Question 23

What layers fold to surround the gut tube?

Answer 23

Parietal mesoderm, ectoderm, and amniotic cavity.

Question 24

What forms the intraembryonic cavity?

Answer 24

Somatic layers of the lateral plate mesoderm folding in on itself anteriorly.

Question 25

What is the intraembryonic cavity the precursor to?

Answer 25

Pericardial, pleural, and peritoneal cavities.

Question 26

What is ectopia cordis?

Answer 26

Failure of the sternum and ribcage to fuse on the midline anteriorly.

Can be corrected surgically, but usually accompanies other anomalies with low survival rate.

It is a thoracic wall defect.

Question 27

What is gastroscisis?

Answer 27

Incomplete closure of the abdominal wall, so the organs protrude out.

It is an abdominal wall defect.

Question 28

What is bladder/coacal exstrophy?

Answer 28

Exposure of the bladder and sometimes external genitalia.

It is a pelvic wall defect.

Question 29

When does the intraembryonic cavity split into the pericardial and peritoneal cavities?

Answer 29

28 days, by the diaphragm.

Question 30

How are the pericardial and peritoneal cavities connected after splitting?

Answer 30

Pericardioperitoneal canals.

Question 31

How do the pericardioperitoneal canals close?

Answer 31

The pleuroperitoneal folds extend from the lateral body wall to fuse with the septum transversum and esophageal mesentery.

Question 32

What is eventration of the diaphragm?

Answer 32

A weakened diaphragm gets pushed by the intestines, invading the thoracic cavity with intestines.

Question 33

What else causes herniation of the diaphragm?

Answer 33

Parasternal and esophageal hernias.

Question 34

What separates the pleural cavities from the pericardial cavity?

Answer 34

Pleuropericardial folds.

Question 35

Describe how the pleural cavities and pericardial cavity get separated.

Answer 35

The lungs push their pleuropericardial folds laterally around the heart, giving it a hug.

Note: The pleuropericardial folds contain the phrenic nerves in them!