4: Respiratory Embryology

Question 1

Laryngeal descent

Answer 1

Larynx is in a high position in neck of neonate -> descends over first two years of life

Question 2

What does respiratory bud development require?

Answer 2

Inductive interactions between endoderm (FGF) + splanchnic mesoderm

Question 3

Primitive vs mature alveoli

Answer 3

Primitive: can still form more alveoli
Mature: can no longer form new alveoli

Question 4

How long are new alveoli added? How many mature alveoli develop post-nasally?

Answer 4

Added until age 8; about 95% of mature alveoli develop post-Na tally

Question 5

What does splanchnic mesoderm form in lungs

Answer 5

Cartilagenous plates, CT, and SM in bronchi + pulmonary CT and capillaries

Question 6

Fetal Breathing Movements (FBM)

Answer 6

Intermittent pattern of breathing that conditions respiratory muscles; are forceful enough to cause aspiration of amniotic fluid which is essential for lung development

Question 7

How is the intra-alveolar fluid in a fetus replaced with air upon delivery?

Answer 7

1. Exits mouth/nose by pressure on thorax during vaginal delivery
2. Through pulmonary capillaries, A’s, V’s, and lymphatics

Question 8

What causes laryngeal atresia

Answer 8

Failure of recanalization of larynx

Question 9

Presentation of laryngeal atresia

Answer 9

1. airways become dilated, lungs are enlarged and filled with fluid
2. CHAOS syndrome (congenital high airway obstruction syndrome): obstruction of upper fetal airway
3. Diaphragm flattened or inverted, fetal ascites and/or hydrops

Question 10

Treatment of laryngeal atresia

Answer 10

Endoscopic dilation of laryngeal web

Question 11

What causes tracheoesophageal fistula

Answer 11

Failure of foregut endoderm to proliferate rapidly enough in relation to rest of body

Question 12

Most common congenital anomaly of lower respiratory tract

Answer 12

Tracheoesophageal fistula

Question 13

Presentation of tracheoesophageal fistula

Answer 13

1. esophageal atresia (blind esophagus) (85%)
2. Cannot swallow, frequently drool, immediate regurgitation when fed
3. Gastric and intestinal contents may reflux through fistula into trachea and lungs
4. Can develop polyhydramnios- fluid cannot enter stomach/intestine for absorption

Question 14

What causes pulmonary agenesis

Answer 14

Respiratory bud fails to split into R/L bronchial buds

Question 15

Unilateral pulmonary agenesis

Answer 15

Abscence of a lung or lobe; other lung will take up a larger portion of space

Question 16

Pulmonary hypoplasia cause

Answer 16

Restriction of fetal thorax due to intrauterine pressure -> decreased hydrostatic pressure on lungs affects stretch receptors and lung growth

Question 17

What significantly increases risk of pulmonary hypoplasia?

Answer 17

Oligohydramnios

Question 18

Two big things that can cause oligohydramnios

Answer 18

Renal agenesis, amnionic leak

Question 19

Presentation of oligohydramnios

Answer 19

pulmonary hypoplasia, altered faces, positioning defects of feet and hands, breech presentation

Question 20

Respiratory Distress Syndrome (RDS) other name

Answer 20

Hyaline membrane disease

Question 21

What causes RDS?

Answer 21

Surfactant deficiency and lungs are under-inflated

Question 22

What % of deaths in premature infants is caused by RDS?

Answer 22

50-70%

Question 23

Type II alveolar cells in RDS

Answer 23

Undergo changes -> incapable of producing surfactant

Question 24

Presentation of RDS

Answer 24

1. rapid, labored breathing develops shortly after birth
2. Tachypnea, nasal flaring, grunting, cyanosis
3. Suprasternal, intercostal, or subcostal retractions