233. Neonatal Physiology Flashcards
What are the five stages of lung development?
- Embryonic stage (4–6 weeks)
- Glandular stage (7–16 weeks)
- Canalicular phase (17–28 weeks)
- Terminal sac period (29–36 weeks)
- Alveolar phase (begins at 36 weeks)
At what gestational age does surfactant synthesis begin?
Around 25 weeks of gestation
What is the significance of surfactant in neonates?
Stabilizes the lung during expiration
What are the main reasons for less efficient respiration in neonates?
- Smaller diameter of airways
- Lower lung volumes
- Highly compliant chest walls
- Higher oxygen consumption
- Immature respiratory muscles
True or False: The narrowest portion of the infant larynx is the cricoid.
True
What can hyperoxia lead to in neonates?
- Surplus of free radicals
- Inhibition of surfactant synthesis
- Increased pulmonary reactivity
What are the hallmarks of fetal circulation?
- Increased pulmonary vascular resistance (PVR)
- Decreased pulmonary blood flow
- Decreased systemic vascular resistance (SVR)
- Right-to-left shunting through ductus arteriosus and foramen ovale
What causes the closure of the ductus venosus after birth?
Removal of the placenta from circulation
How does pulmonary blood flow change after birth?
Increases as pulmonary vascular resistance decreases
What conditions can cause persistent fetal circulation in newborns?
- Arterial hypoxemia
- Acidosis
- Exposure to cold
What is retinopathy of prematurity primarily caused by?
- Oxygen toxicity
- Prematurity
Fill in the blank: Renal function is diminished in neonates due to _______.
[low perfusion pressure and immature glomerular and tubular function]
What is the main compensatory mechanism for cold stress in newborns?
Nonshivering thermogenesis
At birth, what percentage of fetal hemoglobin does a neonate have?
70%–80%
What characterizes central apnea of infancy?
Cessation of breathing for 15 seconds or longer or a shorter pause with bradycardia
