Resp_L03_Flashcards
What are the five phases of prenatal lung development?
Embryonic, pseudoglandular, canalicular, saccular, and alveolar.
In which phase of prenatal lung development do alveolar ducts and surfactant form? At what embryonic age does this occur?
Saccular phase (~26 - 36 weeks)
What does it mean when one says breathing movements in a fetus are paradoxical?
When the diaphragm contracts, the thorax moves invward (chest collapses) and vice versa (normal is other way around).
What cell types exist in the parenchyma of the lung in the pseudoglandular phase (weeks 8 - 17)?
Type II pneumocytes only
In what phase of prenatal lung development do type I pneumocytes differentiate?
Canalicular phase (weeks 16 - 26)
The onset of functional maturation of the lung is marked by appearance of what features in the alveolar type II cells of the fetus?
Lamellar bodies (indicate production of surfactant)
What ratio is used to measure fetal lung maturity? What is the “target” ratio? At what ratio does a neonate have a greater tendency to develop IRDS?
Lecithin/sphingomyelin ratio; >1.8 or 2 = goal,
What are the four types of surfactant-specific proteins found in surfactant?
SP-A, SP-B, SP-C, and SP-D
Which surfactant-specific proteins function as innate immune defenses? Are these present in comercially-produced surfactant?
SP-A and SP-D; SP-A is not present in comercially-produced surfactant.
Which surfactant-specific proteins are critical for surface activity (such as surface tension)? Are these present in comercially-produced surfactant?
SP-B and SP-C; yes
What is a common inhibitor of surfactant production in the fetus?
Maternal diabetes
What are three characteristics of alveolar maturation in late fetal life?
Increased number & size of alveoli, thinning of ceonnective tissue septa between alveoli, and flattening of alveolar epithelium.
What are two types of stimuli that encourage the first breath in a neonate? Give examples of each.
Chemical stimuli (increased PCO2, decreased PO2) and environmental stimuli (cooling, light, sound, J receptors stimulated by pressure)
What is the main/most important function of the first breath?
Establishes functional residual capacity
What is the main factor that leads to absorption of fetal lung fluid in the neonate? What brings this about in the birthing process?
Perinatal epinephrine surge, brought on by the forceful nature of a delivery.
What are two factors that enhance absorption of fetal lung fluid?
Thyroid & steroid hormones, alveolar-capillary pressure gradient.
How efficient is the breathing apparatus in the newborn? What does this mean in terms of energy expenditure?
Not very efficient due to chest shape and poor respiratory muscle development; leads to loss of energy with every breath.
How does the ventilation-perfusion relationship of the neonate evolve? What two factors result in this change?
Initially low, normalizes over several months. Two factors: # of pulmonary arteries decrease overtime to match # of alveoli; and there is a decrease in vascular resistance in the lungs as baby starts to breath allowing more blood flow to the lungs.
How does the breathing pattern of the neonate change from when it is in the uterus to post-partum?
Episodic inside the uterus, continues post-partum.
Respiratory pauses such as periodic breathing or central apnea can still occur in a neonate. Wha tis the most important thing that can be done when this happens?
Arousal; wake the baby up!
How does the neonate’s body react to hypoxia compared to a more aged/mature baby? Is this good or bad?
Neonate: hypoxia leads to decreased ventilation (should normally lead to increased ventilation). Can be bad.
