Respiratory-Embryo

Question 1

What are the five stages of lung development?

Answer 1

• Embryonic
• Psuedoglandular
• Canalicular
• Saccular
• Alveolar

Question 2

Describe the embryonic stage of lung development?

Answer 2

This occurs from weeks 4-7 in utero an consists of the formation of the midline trachea down to the teriary bronchi from an initial ‘lung bud’

Error during this stage can result in a TE fistula

Question 3

Describe the pseudoglandular stage of lung development?

Answer 3

This occurs from weeks 5-16 and consists of the formaiton of endodermal tubules down to terminal bronchioles

Respiration is still not possible if born during this phase

Question 4

Describe the canalicular stage of lung development?

Answer 4

This occurs during weeks 18-26 and consists of the formation of terminal bronchioles, respiratory bronchioles, and alveolar ducts

Question 5

Respiration is possible in a newborn if born when?

Answer 5

25+ weeks

Question 6

Describe the saccular stage of lung development?

Answer 6

This occurs from week 26- birth and consists of formation of the alveolar ducts and teminal sacs AND

**formation of pneumocytes**

Question 7

Describe the alveolar stage of lung development?

Answer 7

This occurs from birth to about 8 yrs of life and consists of formation of adult alveoli (i.e. alveoli are still being made after birth)

Question 8

How does breathing occur in utero?

Answer 8

via aspiration and expulsion of amniotic fluid (note that vascular resistance increases throughout gestation and that, at birth when fluid gets replaced by air, pulmonary vascular resistance drops and the lungs expand)

Question 9

When is surfactant produced in utero?

Answer 9

beginning at week 26, but mature levels are not achieved until around week 35

Question 10

Pulmonary hypoplasia, or poorly developed bronchial trees, is classically seen in what syndrome?

Answer 10

Potter sequence due to oligohydramnios

Question 11

Describe type I pneumocytes

Answer 11

These represent 97% of alveolar surfaces and are squamous (flat) in shape for optimal gas exchange

Question 12

Describe type II pneumocytes

Answer 12

These are cuboidal in shape and secrete pulmonary surfactant to decrease alveolar surface tension and prevent alveolar collapse, decrease lung recoil, and increae compliance

These also serve as stem cells for both type I and II pneumocytes

Question 13

What is the eqn for collaping pressure (P) of the lung?

Answer 13

P= 2(surface tension)/radius

Alveoli have an increased tendency to collpase on expiration as the radius decreases

Question 14

What is the composition of surfactant?

Answer 14

lecithins, the most important of which is DPPC

Question 15

What are club cells?

Answer 15

These are found in alveoli and secrete components of surfactant, as well as degrading toxins and acting as reserve cells

Question 16

Describe neonatal respiratory distress syndrome

Answer 16

This results from surfactant deficiency, typically in premature newborns, that is characterized by increased alveoli surface tension causing the lungs to collapse

Question 17

What are the risk factors for NRDS?

Answer 17

prematurity, maternal DN (due to increased fetal insulin), and C-section delivery due to decreased release of fetal glucocorticoids

Question 18

What are some screening tests of NRDS?

Answer 18

1) lecithin-sphingomyelin (L/S) ratio in amniotic fluid (2+ is healthy and less than 1.5 predicts NRDS)
- foam stability index test
- surfactant:albumin ratio

Question 19

What are some potential complications of NRDS?

Answer 19

metabolic acidosis, PDA, necrotizing enterocolitis

Question 20

Therapeautic supplementa O2 in a NRDS baby can result in what?

Answer 20

Retinopathy of prematurity

Intraventricular hemorrhage

Bronchopulmonary dysplasia

RIB

Question 21

How might NRDS appear on a high resolution CT scan of the lungs?

Answer 21

ground glass appearance