Fetal and Newborn Pulmonary Physiology

Question 1

what are the 5 stages of lung development

Answer 1

embryonic (0-8)–> pseudoglandular (8-17)–>canalicular (16-26)–>saccular (24-38)–>alveolar (after birth)

Question 2

what type of tissue are the lungs developing from

Answer 2

endoderm

Question 3

when does alveolar formation begin in humans

Answer 3

28 wks

Question 4

when does is the most major increase in the number of alveoli

Answer 4

after birth

Question 5

how is lung growth regulated in the fetus

Answer 5

lung fluid stimulates growth/external compression inhibits growth

Question 6

what is developing/occurring during the embryonic phase?

Answer 6

• paradoxical breathing movement
• main bronchus and the 5 lobes
• aortic arches, lung buds, and pulmonary plexus

Question 7

what is developing during the pseudoglandular phase

Answer 7

• lungs resemble a gland
• type II pneumos are making amniotic fluid
• capillaries are developing

Question 8

what is developing during the canalicular phase

Answer 8

• type I pneumo out of type II cells
• alteration of the epithelium
• maturity of the lungs can be measured near the end

Question 9

what is developing during the saccular phase

Answer 9

• clusters of sacs from on the terminal bronchioli
• basically everything but the alveoli are completely developed now
• 2 networks of capillaries are developing around the sacs

Question 10

what is surfactant stored in?

Answer 10

Lamellar bodies

Question 11

list 4 reasons why the fetal lungs are not very good at respiration at birth

Answer 11

1. filled with fluid
2. pulmonary vascular resistance is high
3. compliance of the lung is low
4. chest wall compliance is too high

Question 12

what 4 changes then need to occur at birth for efficient gas exchange?

Answer 12

1. breathing and ventilation must start
2. FRC must be established
3. pulmonary vasculature must dilate
4. fetal pulmonary fluid must be absorbed

Question 13

What are the surfactant specifc proteins?

Answer 13

A/D: immuno function

B/C: critical for pulmonary surface activity

Question 14

Lecithin/sphingomyelin normal ratio?

Answer 14

1.8-2.0

Question 15

What L/S ratio would indicate a high risk for infantile respiratory distress syndrome?

Question 16

name some stimulators of surfactant synthesis

Answer 16

• glucocorticoids
• thyroid hormones
• cAMP
• epidermal growth factor
• beta-adrenergic agonists
• purinoceptor agonists

Question 17

what is a major inhibitor of surfactant synthesis

Answer 17

maternal diabetes

Question 18

at what developmental stage can you start to measure L/S for lung maturity?

Answer 18

cannalicular

Question 19

what is developing during the alveolar phase

Answer 19

• 1/3 of the alveoli have developed
• then they increase in size and number
• thinning of the alveolar lining
• thinning of the CT septa between alveoli

Question 20

what hormones promotes absorption of fetal lung fluid?

Answer 20

1. epinephrine –> transepithelial Na transport
2. thyroid and steroid hormones
3. pressure gradient from airspaces to capillaries

Question 21

describe the respiratory mechanics (lung compliance)

Answer 21

• low lung compliance
• highly compliant cw/poor chest recoil
• loss of energy/intrinsic mechanical properties of respiratory muscle

Question 22

how does pulmonary circulation change after birth

Answer 22

• ratio of small pulmonary arteries to alveoli decreases 2-fold
• vascular walls gradually thin
• pulmonary vascular resistance continues to fall

Question 23

describe respiratory responses to stimuli

Answer 23

1. response to CO2 is increased

2. response to hypoxia is biphasic - initial hyperventilation followed by respiratory attenuation of even apnea