Physiology of the Neonate
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The bronchial tree of the fetal lungs is fully developed by 16 weeks of gestation. By 28 weeks, the pre-acinar pattern of airways, arteries and veins is formed with capillaries in the alveolar walls. Type II pneumocytes of the alveolar epithelium are seen by 24 weeks of gestation, and surfactant can be detected in lung extracts from 23 weeks onwards and in fetal tracheal fluid by 28 weeks. Surfactant production in the fetal lung is increased by the administration of cortisol and thyroxine to the mother. Surfactant production is associated with an increase in lecithin in the amniotic fluid. The concentration of sphingomyelin is constant throughout pregnancy, and a lecithin/sphingomyelin ratio greater than 2 is normally present by 36 weeks of gestation.
Maternal and neonatal physiology
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2015
The bronchial tree of the foetal lungs is fully developed by 16 weeks of gestation. By 28 weeks, the pre-acinar pattern of airways, arteries and veins is formed with capillaries in the alveolar walls. Type II pneumocytes of the alveolar epithelium are seen by 24 weeks of gestation, and surfactant can be detected in lung extracts from 23 weeks onwards and in foetal tracheal fluid by 28 weeks. Surfactant production in the foetal lung is increased by the administration of cortisol and thyroxine to the mother. Surfactant production is associated with an increase in lecithin in the amniotic fluid. The concentration of sphingomyelin is constant throughout pregnancy, and a lecithin/sphingomyelin ratio greater than 2 is normally present by 36 weeks of gestation.
Developmental Aspects of the Alveolar Epithelium and the Pulmonary Surfactant System
Jacques R. Bourbon in Pulmonary Surfactant: Biochemical, Functional, Regulatory, and Clinical Concepts, 2019
A physiologic role of endogenous corticosteroid hormones is supported by a number of observations. In the sheep fetus, a temporal association has been evidenced between lung maturation and a rise of circulating corticosteroids in fetal circulation.308,309 In humans, Cortisol rises fivefold in amniotic fluid at about 35 weeks310 and corticosterone increases slightly at 36 weeks and sharply near term in fetal cord serum,311 which may be related to the elevated rate of surfactant accumulation. A similar correlation was established in other species, for instance, rat and mouse. Anencephaly in the human fetus, although it little affected lung growth and alveolization,312 tremendously reduced the lecithin/sphingomyelin ratio in amniotic fluid at the same gestational age.313In utero or in ovo decapitation or hypophysectomy have been shown to delay lung maturation, to reduce lung PC content and synthetic rate, and to alter pulmonary physical properties.195,196,271,314–319 Although this may have been due to hormone deficiencies other than adrenal hormones, the compensatory effects of exogenously administered glucocorticoids demonstrated that they were primarily involved. Metopirone, an inhibitor of Cortisol synthesis through competitive inhibition of the enzyme 11 β-hydroxylase, has been reported to delay lung maturation, surfactant biosynthesis, and onset of antioxidant activities,320,321 although few effects were observed in other instances.322,323
Echogenic particles in the amniotic fluid of term low-risk pregnant women: does it have a clinical significance?
Published in Journal of Obstetrics and Gynaecology, 2021
Gul Nihal Buyuk, Z. Asli Oskovi-Kaplan, Serkan Kahyaoglu, Yaprak Engin-Ustun
Older studies on free-floating particles in amniotic fluid proposed that these images would represent foetal lung maturity in the last trimester and was associated with vernix and lecithin/sphingomyelin ratio (Gross et al. 1985). Higher maternal serum alpha-fetoprotein levels were also reported in early second trimester pregnant women (Hallak et al. 1993). Several hypotheses on the cause of these particles have been proposed including foetal skin fragments, blood, vernix caseosa, and meconium (Hallak et al. 1993). The acrania-anencephaly sequence in the first trimester, harlequin ichthyosis, and epidermolysis bullosa are other rare causes of echogenic amniotic fluid appearance (Cafici and Sepulveda 2003; Dural et al. 2014).
Related Knowledge Centers
- Amniotic Fluid
- Fetus
- Infant Respiratory Distress Syndrome
- Lecithin
- Sphingomyelin
- Surfactant
- Glycoprotein
- Preterm Birth
- Biophysical Profile
- Pulmonary Alveolus