Fetal and newborn pulmonary physiology Flashcards
when does alveolar formation begin?
28th week gestation
what are the milestone phases of lung development?
embryonic psueoglandular canalicular saccular alveolar
during what week does surfactant start being produced? during which phase of lung development is this?
25th week
saccular
what events occur during the embryonic phase of lung development?
first segments appear in the 5 lobes
pulmonary vessels have formed
during which phase of lung development can precursors of pneumocytes be discerned in the respiratory sections as cubic epithelium?
pseudoglandular
during which phase do type I pneumocytes differentiate from type II pneumocytes?
canalicular
during which phase is amniotic fluid produced by lung epithelium?
canalicular
at what point can lung maturity be based upon the activity of type II pneumocytes?
from canalicular phase onward
what is the main feature of the saccular phase of lung development?
whole clusters of sacs form on the terminal bronchioli
phase: primary septa contain two networks of capillaries coming from neighboring sacculi
saccular phase
phase: fibroblasts begin to produce extracellular material in the interductal and intersaccular space
saccular phase
by the end of which phase have all generations of conducting and respiratory branches been generated?
saccular
the onset of functional maturation of the lung is marked by the appearance of what structures? where are they located?
lamellar bodies
alveolar type II cells
the ratio of what compounds in amniotic fluid is a measure of fetal lung maturity?
lecithin / sphingomyelin
what happens to the lecithin / sphingomyelin ratio at week 32?
lecithin production increases rapidly
sphingomyelin production decreases
a lecithin / sphingomyelin ratio below what value indicates poor lung maturity?
1.8
what are the functions of surfactant specific proteins?
immune defense
surface activity
which surfactant specific proteins are critical for surface activity?
SP-B
SP-C
what are stimulators of surfactant synthesis in the saccular phase of lung development?
glucocorticoids thyroid hormones cAMP epidermal growth factor beta adrenergic agonists purinoceptor agonists
what is an inhibitor of surfactant synthesis in the saccular phase of lung development?
maternal diabetes
what events occur in late fetal life during the alveolar maturation phase of lung development?
increase number and size of alveoli
thinning of CT septa between alveoli
flatter alveolar epithelium
what is the role of the perinatal EPI surge?
activates transepithelial sodium transport to absorb all the fluid in the lungs
perinatal absorption of lung fluid is enhanced by what factors?
thyroid and steroid hormones
alveolar capillary pressure gradient
what is the status of neonatal lung compliance?
low static and dynamic compliance:
low lung compliance
high chest wall compliance
viscous properties of newborn lung tissues
distortion of pliable newborn chest
