Fetal Development and Lung Development Flashcards
What are the three stages of development in utero?
Conception (first two weeks), Embryonic (weeks 3-12), and Fetal (weeks 12-40)
What measurement do we use to track growth in the first trimester?
Crown to rump
At what week gestation are babies viable?
Usually 24 weeks, sometimes as low as 22
What are the three germ layers?
Ectoderm, mesoderm, endoderm
What germ layer do the skin, CNS and PNS, and eyes form from?
Ectoderm
What germ layer do the CVS, bones, and kidneys form from?
Mesoderm
What germ layer do the lungs and GI system form from?
Endoderm
When will miscarriage most often occur and why?
The first 12 weeks because there is so much development so if something goes wrong it usually happens here
What are the 5 stages of lung development?
Embryonic, psuedoglandular, canaliccular, and saccular
When is the embryonic period of lung development and what happens during it?
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!!!
When is the embryonic period and what occurs during it?
- 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
What factor contributes most greatly to the development of a fetus’s lungs?
The stretching of the lungs as the diaphragm works to bring amniotic fluid in and out of the lungs
How can we tell how developed a fetus’s lungs are?
Measuring components of surfactant present in the amniotic fluid using amniocentesis. Called an L/S ratio that measures lecithen and sphygomyelin levels
When is the pseudoglandular phase and what occurs?
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
What is choanal atresia?
When the membrane between the nasal cavity and oral cavity does not disappear during the pseudoglandular phase.
When is the canalicular period and what happens during it?
17-26 weeks
- Capillary networks form
- Branching of airways completes
- Fetal lung fluid is produced
- Type I and II cells differentiate
When is the saccular period and what happens during it?
27-36 weeks
- True alveoli form at 30 weeks
- More mature surfactant appears
What is the alveolar period and what happens during it?
Alveoli proliferate and lungs are as mature as they can get
Why is surfactant important?
Lowers surface tension of the lungs and allows the alveoli to stay open
What are the indications for doing an L/S ratio and what level indicates mature lungs?
Premature labor, PROM, whenever early delivery is possible. >2.0 means lungs are mature
What is a fluorescent polarization test?
Measures surfactant to albumin ratio to determine lung maturity. Kit is no longer made
What is a lamellar body count?
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
What is the phosphatidylglycerol test?
Measure of phosphatidylglycerol where >2 tells us lungs are mature
