Editing Lung (section)

=== After birth ===
At [[Childbirth|birth]], the baby's lungs are filled with fluid secreted by the lungs and are not inflated. [[Adaptation to extrauterine life#Breathing and circulation|After birth]] the infant's [[central nervous system]] reacts to the sudden change in temperature and environment. This triggers the first breath, within about ten seconds after delivery.<ref name="Medline2015">{{cite web |title=Changes in the newborn at birth |url=https://medlineplus.gov/ency/article/002395.htm |website=MedlinePlus Medical Encyclopedia }}</ref> Before birth, the lungs are filled with fetal lung fluid.<ref>{{cite journal|title=Fetal lung liquid secretion|journal=American Journal of Respiratory Cell and Molecular Biology|volume=25|issue=1|pages=8–10|doi=10.1165/ajrcmb.25.1.f211|pmid=11472968|year=2001|last1=O'Brodovich|first1=Hugh}}</ref>      After the first breath, the fluid is quickly absorbed into the body or exhaled. The [[vascular resistance|resistance]] in the lung's blood vessels decreases giving an increased surface area for gas exchange, and the lungs begin to breathe spontaneously. This accompanies [[Adaptation to extrauterine life|other changes]] which result in an increased amount of blood entering the lung tissues.<ref name= Medline2015 />

At birth, the lungs are very undeveloped with only around one sixth of the alveoli of the adult lung present.<ref name="Sadler"/> The alveoli continue to form into early adulthood, and their ability to form when necessary is seen in the regeneration of the lung.<ref name="Schittny">{{cite journal|last1=Schittny|first1=JC|last2=Mund|first2=SI|last3=Stampanoni|first3=M|title=Evidence and structural mechanism for late lung alveolarization|journal=American Journal of Physiology. Lung Cellular and Molecular Physiology|date=February 2008|volume=294|issue=2|pages=L246–254|doi=10.1152/ajplung.00296.2007|pmid=18032698|citeseerx=10.1.1.420.7315}}</ref><ref name="SchittnyJC">{{cite journal|last1=Schittny|first1=JC|title=Development of the lung|journal=Cell and Tissue Research|date=March 2017|volume=367|issue=3|pages=427–444|doi=10.1007/s00441-016-2545-0|pmid=28144783|pmc=5320013}}</ref> Alveolar septa have a double [[Capillary#Structure|capillary network]] instead of the single network of the developed lung. Only after the maturation of the capillary network can the lung enter a normal phase of growth. Following the early growth in numbers of alveoli there is another stage of the alveoli being enlarged.<ref>{{cite journal|last1=Burri|first1=PH|title=Fetal and postnatal development of the lung|journal=Annual Review of Physiology|date=1984|volume=46|pages=617–628|pmid=6370120|doi=10.1146/annurev.ph.46.030184.003153}}</ref>