Embryology

Question 1

What are the five stages of lung development?

Answer 1

“Every pulmonologist can see alveoli”
1. Embryonic
2. Pseudoglandular
3. Canalicular
4. Saccular
5. Alveolar

Question 2

The respiratory epithelium that lines the airways is derived from the _

Answer 2

The respiratory epithelium that lines the airways is derived from the endoderm

Question 3

The cartilage, muscle, and lung tissue found in the RT is all derived from the _

Answer 3

The cartilage, muscle, and lung tissue found in the RT is all derived from the mesoderm

Question 4

As early as 26 days after fertilization, the increase in _ acid causes the formation of the _ (early lung structure)

Answer 4

As early as 26 days after fertilization, the increase in retinoic acid causes the formation of the lung bud

Question 5

The lung bud branches off the anterior aspect of the developing _

Answer 5

The lung bud branches off the anterior aspect of the developing foregut
* This portion of the foregut will later become the esophagus

Question 6

At first, the lung bud is open to the foregut; but eventually the _ will form to separate the two tubes: the trachea and the esophagus

Answer 6

At first, the lung bud is open to the foregut; but eventually the tracheoesophageal septum will form to separate the two tubes: the trachea and the esophagus

Question 7

The formation of the tracheoesophageal septum is vital; abnormal septation can result in _ or _

Answer 7

The formation of the tracheoesophageal septum is vital; abnormal septation can result in esophageal atresia or tracheoesophageal fistula

Question 8

The embryonic stage lasts from week _ to _ and involves the development of _ –> _ –> _

Answer 8

The embryonic stage lasts from week 4-7 and involves the development of lung bud –> bronchial buds –> pulmonary vasculature

Question 9

The pseudoglandular stage is marked by extensive _ which is signaled by _

Answer 9

The pseudoglandular stage is marked by extensive branching of airways and blood vessels which is signaled by fibroblast growth factors

Question 10

Respiratory bronchioles become prominent in the _ stage of development

Answer 10

Respiratory bronchioles become prominent in the canalicular stage of development
* Rudimentary acini also form (respiratory bronchiole + alveolar duct and sac)
* Capillaries become more extensive

Question 11

Pseudoglandular stage of gestation lasts from weeks _ to _

Answer 11

Pseudoglandular stage of gestation lasts from weeks 5-17

Question 12

The canalicular stage of gestation lasts from weeks _ to _

Answer 12

The canalicular stage of gestation lasts from weeks 16-25

Question 13

The saccular stage lasts from weeks _ to _

Answer 13

The saccular stage lasts from weeks 24- birth

Question 14

What changes occur during the saccular stage?

Answer 14

During the saccular stage, many more terminal sacs develop
* Epithelium becomes very thin
* Septation begins to divide the alevolar sacs into small units
* Type I and II pneumocytes become more prominent

Question 15

Alveolar stage lasts from weeks _ to _

Answer 15

Alveolar stage lasts from weeks 32- birth
* Alveolarization occurs as we have more acini and greater vascularization

Question 16

At birth only about _ percent of alveoli are mature, the remaining _ mature after birth

Answer 16

At birth only about 5% of alveoli are mature, the remaining 95% mature after birth
* Lung maturation continues until age 8

Question 17

Inspiration-like movements begin early in utero; aspiration of _ helps to stimulate lung development

Answer 17

Inspiration-like movements begin early in utero; aspiration of amniotic fluid helps to stimulate lung development
* When babies are born their first breath triggers rapid resorption of amniotic fluid into the alveolar capillaries and lymphatic system

Question 18

Esophageal atresia and tracheoesophageal fistulas prevent the fetus from swallowing amniotic fluid in utero, therefore most of them are detected prenatally due to _

Answer 18

Esophageal atresia and tracheoesophageal fistulas prevent the fetus from swallowing amniotic fluid in utero, therefore most of them are detected prenatally due to polyhydramnios
* Signs after birth: coughing, choking, drooling, cyanosis

Question 19

Pulmonary hypoplasia can be a primary genetic condition or it can be secondary to insufficient amniotic fluid called _

Answer 19

Pulmonary hypoplasia can be a primary genetic condition or it can be secondary to insufficient amniotic fluid called oligohydramnios
* Other causes include diaphragmatic hernia, abnormal diaphragmatic activity

Question 20

_ is a developmental defect in the diaphragm that allows abdominal contents to protrude up into the thoracic cavity and is a “can’t miss” cause of NRDS after birth

Answer 20

Congenital Diaphragmatic Hernia is a developmental defect in the diaphragm that allows abdominal contents to protrude up into the thoracic cavity and is a “can’t miss” cause of NRDS after birth

Question 21

Signs of NRDS

Answer 21

Classic presentation of NRDS is a neonate showing respiratory distress
* Tachypnea (more than 60 breaths per minute)
* Subcostal and intercostal retractions
* Nasal flaring
* Cyanosis
* Expiratory grunting

Question 22

The most common reason for respiratory distress in newborns is _ which is failure to clear alveolar fluid from the lungs

Answer 22

The most common reason for respiratory distress in newborns is transient tachypnea which is failure to clear alveolar fluid from the lungs
* Chest x-ray shows over inflated lungs, interstitial edema, small pleural effusions

Question 23

In neonates with NRDS the chest x-ray will show _

Answer 23

In neonates with NRDS the chest x-ray will show ground-glass infiltrates in all lung fields
* Ground glass = diffuse, fine reticulonodular infiltrates

Question 24

NRDS can be prevented in utero by administering _ to the mother 2-7 days before delivery

Answer 24

NRDS can be prevented in utero by administering corticosteroid to the mother 2-7 days before delivery