Fetal Development and Lung Development

Question 1

What are the three stages of development in utero?

Answer 1

Conception (first two weeks), Embryonic (weeks 3-12), and Fetal (weeks 12-40)

Question 2

What measurement do we use to track growth in the first trimester?

Answer 2

Crown to rump

Question 3

At what week gestation are babies viable?

Answer 3

Usually 24 weeks, sometimes as low as 22

Question 4

What are the three germ layers?

Answer 4

Ectoderm, mesoderm, endoderm

Question 5

What germ layer do the skin, CNS and PNS, and eyes form from?

Answer 5

Ectoderm

Question 6

What germ layer do the CVS, bones, and kidneys form from?

Answer 6

Mesoderm

Question 7

What germ layer do the lungs and GI system form from?

Answer 7

Endoderm

Question 8

When will miscarriage most often occur and why?

Answer 8

The first 12 weeks because there is so much development so if something goes wrong it usually happens here

Question 9

What are the 5 stages of lung development?

Answer 9

Embryonic, psuedoglandular, canaliccular, and saccular

Question 10

When is the embryonic period of lung development and what happens during it?

Answer 10

0-6 weeks. At 26 days the lung buds begin to emerge from the endoderm that forms the primordial pharyngeal tissue.
- Mainstem bronchi formed, tracheobronchial tree emerges, tracheoesophageal septum formed.
- Mesenchyme develops into pulmonary interstitium, smooth muscle, blood vessels, and cartilage.
- Right and left pulmonary veins emerge
- Diaphragm is formed!!!

Question 11

When is the embryonic period and what occurs during it?

Answer 11

• 0-6 weeks
• Mainstem bronchi, tracheobronchial tree, and tracheoesophageal septum formed
• Airway divides and lung tissue develops
• Mesenchyme develops into interstitium, smooth muscle, blood vessels, and cartilage
• Right and left pulmonary veins emerge
• DIAPHRAGM IS FORMED

Question 12

What factor contributes most greatly to the development of a fetus’s lungs?

Answer 12

The stretching of the lungs as the diaphragm works to bring amniotic fluid in and out of the lungs

Question 13

How can we tell how developed a fetus’s lungs are?

Answer 13

Measuring components of surfactant present in the amniotic fluid using amniocentesis. Called an L/S ratio that measures lecithen and sphygomyelin levels

Question 14

When is the pseudoglandular phase and what occurs?

Answer 14

7-16 weeks
- Airway cells differentiate into goblet cells and ciliated pseudostratified columnar cells
- Conducting airways complete
- Nasal and oral cavities lose membrane between them
- Larynx develops

Question 15

What is choanal atresia?

Answer 15

When the membrane between the nasal cavity and oral cavity does not disappear during the pseudoglandular phase.

Question 16

When is the canalicular period and what happens during it?

Answer 16

17-26 weeks
- Capillary networks form
- Branching of airways completes
- Fetal lung fluid is produced
- Type I and II cells differentiate

Question 17

When is the saccular period and what happens during it?

Answer 17

27-36 weeks
- True alveoli form at 30 weeks
- More mature surfactant appears

Question 18

What is the alveolar period and what happens during it?

Answer 18

Alveoli proliferate and lungs are as mature as they can get

Question 19

Why is surfactant important?

Answer 19

Lowers surface tension of the lungs and allows the alveoli to stay open

Question 20

What are the indications for doing an L/S ratio and what level indicates mature lungs?

Answer 20

Premature labor, PROM, whenever early delivery is possible. >2.0 means lungs are mature

Question 21

What is a fluorescent polarization test?

Answer 21

Measures surfactant to albumin ratio to determine lung maturity. Kit is no longer made

Question 22

What is a lamellar body count?

Answer 22

Lamellar bodies store and secrete surfactant in type II alveolar cells and are shed from the lung into the amniotic fluid. >50,000 tells us the lungs are mature

Question 23

What is the phosphatidylglycerol test?

Answer 23

Measure of phosphatidylglycerol where >2 tells us lungs are mature