Respiratory System Development

Question 1

What are fetal breathing movements?

What else is required w/ them for normal lung development?

Answer 1

priming lungs for breathing - breath in amniotic fluid
need adequate space for thoracic growth
adequate amniotic fluid volume

Question 2

How does hyaline membrane disease present?

What causes it?

Answer 2

ground glass appearance of lungs in chest x ray

occurs bc of lack of surfactant in terminal sac stage

Question 3

When do secondary bronchi form?

Answer 3

week 6

Question 4

At what point do you have all your bronchopulmonary segments to the terminal bronchioles?
How many orders of branches are there?

Answer 4

24 weeks

17 orders

Question 5

What and when happens in pseudglandular lung development?

Answer 5

5-17 weeks
terminal bronchioles formed
connective tissue from splanchnic mesoderm formed
capillaries far away from bronchioles
can’t survive if you only get to this point

Question 6

When do primary brochial buds form?

Answer 6

week 5

Question 7

What are the two groups of people whose lungs develop fastest?

Answer 7

african americans
females
(caucasian males develop the slowest)

Question 8

What causes congenital diaphragmatic hernia?

What is the other name for it?

Answer 8

septum transversum and pleuroperitoneal folds do not fuse

foramen of bochdalek

Question 9

When/what happens in alveolar development?

Answer 9

32 weeks - 8 years
alveolocapillary membrane formed
primitive alveoli start to mature - 90% of mature alveoli formed after birth
most at 3 yrs, don’t finish until 8 yrs

Question 10

What are laryngeal webs?

Answer 10

tissue btw vocal folds = incomplete atresia
usually present in infancy w/ respiratory stress and stridor
caused by failure of recanilization

Question 11

What canals do bronchial buds grow into?

Answer 11

pericrdial-peritoneal canals

Question 12

When is the tracheoesophageal septum formed?

Answer 12

week 5

Question 13

What are signs of respiratory distress in an infant?

Answer 13

tachypnea
nasal flaring
suprasternal, intercostal, or subcostal retractions
grunting
cyanosis

Question 14

What does the primitive pharynx and respiratory diverticulum form from?

Answer 14

endoderm from 6th arch

Question 15

What is oligohydramnios?

What does it cause?

Answer 15

too little amniotic fluid

severe cases –> retards lung development –> pulmonary hypoplasia

Question 16

When do tertiary bronchi form?

How many are there?

Answer 16

week 7
10 right
9 left

Question 17

What is the laryngotracheal diverticulum?

Answer 17

Bud of endoderm that is the early trachea

Question 18

How many secondary bronchi are there?

Answer 18

3 on right: superior, middle, inferior

2 on left: superior, inferior

Question 19

Oligohydramnios at what stage significantly increases risk of pulmonary hypoplasia?

Answer 19

oliogohyramnios prior to 26 weeks

Question 20

When/what happens in canalicular lung development?

Answer 20

16-25 weeks
vessels are much closer to terminal sacs now
primordial alveolar ducts have formed from respiratory bronchioles –> terminal sacs
can survive w/ medical intervention

Question 21

What is laryngomalacia?

Answer 21

collapse of the supraglottic structures during inspiration = most common congenital anomaly of the larynx
mechanism unknown

Question 22

How does congenital diaphragmatic hernia present?

Answer 22

will see intestines in thorax w/ heart pushed over to the right
barrel-shaped thorax
abdomen scaphoid shaped
absence of breath sounds ipsilaterally

Question 23

What is recanalization and when does it occur in the larynx?

Answer 23

sequence of apoptosis that allows the endodermal proliferation to turn into a tube again –> allows for laryngeal ventricals and vocal and vestibular folds
10th week

Question 24

When is surfactant detectible in amniotic fluid?

Answer 24

starting at week 25

Question 25

How many arytenoid swellings are there?

Answer 25

1, 2, 3, 4, 5 disappears, 6

Question 26

What is the hypobranchial eminence?

Answer 26

comes from arytenoid arch 4 –> turns into epiglottis

Question 27

What are the tracheoesophageal folds and septum?

Answer 27

folds are the first bit of endoderm that separate the growing trachea and esophagus (coronal plane) –> once grown together = tracheoesophageal septum

Question 28

What is laryngeal atresia?

Answer 28

failure of recanilization –> larynx is completely closed

Question 29

What is the most common kind of tracheoesophageal fistula?

Answer 29

esophageal atresia = blind end esophagus

84% of cases are this

Question 30

What are the 2 types of Tracheoesophageal fistula?

Answer 30

esophageal atresia = blind end esophagus

trachoesophageal fistula = abnormal passage btw trachea and esophagus

Question 31

What are the arytenoid swellings made of?

What do they turn into?

Answer 31

neural crest covered in endoderm

turn into cartilage

Question 32

What neonatal condition can be a risk factor for TE fistula?

Answer 32

polyhydramnios (too much amniotic fluid)

Question 33

What general part of the lung forms first?

Answer 33

superior part

Question 34

When/what happens in terminal sac lung development?

Answer 34

24 weeks - birth
type I and II pneumocytes differentiate 
surfactant now produced
lymphatic capillaries developed
will survive

Question 35

How is intra-alveolar fluid cleared at birth?

Answer 35

by pressure on thorax during vaginal delivery –> out mouth and nose
into pulmonary capillaries, arteries, and veins
into lymphatics

Question 36

What are congenital lung cysts filled with?

Why do we think they form?

Answer 36

air or fluid - looks like honeycomb on x ray

thought to be bc of disturbance in bronchial dev during late fetal life

Question 37

What causes a TE fistula?

When would it occur?

Answer 37

problem w/ tracheal esophageal folds

week 5

Question 38

What are the 4 stages of lung development?

Answer 38

1. pseudoglandular (5-17 weeks)
2. canalicular (16-25 weeks)
3. terminal sac (24 weeks - birth)
4. alveolar (32 weeks - 8 years)