Maturation of the Lungs
Maturation of lungs
The lungs have to undergo 4 stages in other to mature. The stages are:
a) Pseudoglandular period (6-16 weeks)
b) Canalicular period (16-26 weeks)
c) Terminal sac stage (26 weeks to birth)
d) Alveolar period (32 weeks to 8 years)
The lungs have to undergo 4 stages in other to mature. The stages are:
a) Pseudoglandular period (6-16 weeks)
b) Canalicular period (16-26 weeks)
c) Terminal sac stage (26 weeks to birth)
d) Alveolar period (32 weeks to 8 years)
Available at http://www.cincinnatichildrens.org/research/divisions/p/pulmonary-bio/lung-morphogenesis/
Pseudoglandular period
In the beginning of this period, the lungs only contain exocrine gland and when the fetus reached 16 weeks, most of the important elements of the lung have been created except the part which involves gas exchange. Any fetus born during this period will not survives because no respiration able to take place.
In the beginning of this period, the lungs only contain exocrine gland and when the fetus reached 16 weeks, most of the important elements of the lung have been created except the part which involves gas exchange. Any fetus born during this period will not survives because no respiration able to take place.
Available at http://basenat.u707.jussieu.fr/site_respirare/index.php?option=com_content&view=article&id=59&Itemid=30&lang=en&limit
Canalicular period
Canalicular means passage and this period refer to the lungs tree. The distal part of the lungs mature later than the proximal part and because of this the canalicular period will overlapped with the pseudoglandular period. During this period, the lung tissue will be highly vascularized and the lumen of the bronchi and terminal bronchioles will enlarge. Towards the end of the canalicular period, approximately between 24-26 weeks of gestation, it is possible for the respiration to occur after the passages have completed up to the primordial alveolar sacs and the lung tissues is well vascularized. If the fetus is born during this period, he/she may survives with excellent neonatal intensive care unit. The pre-mature neonate is lacks of surfactant which prevents the lungs from collapsing. It is a fluid that reach with phospholipids and proteins. |
Terminal sac stage
Many more terminal sacs is forms during this period and the wall of the alveolar sac becoming thin and more vascularized. The blood-air barrier is established between the alveolar sac epithelial layer and the capillaries and very important for the gas exchange to occur. Type I pneumocytes is a squamous epithelial cells that lined the terminal sacs and this is the place where the gas exchange take place. Type II pneumocytes is a secretory epithelial cells that secrete surfactant and distributed among the type I pneumocytes.
Many more terminal sacs is forms during this period and the wall of the alveolar sac becoming thin and more vascularized. The blood-air barrier is established between the alveolar sac epithelial layer and the capillaries and very important for the gas exchange to occur. Type I pneumocytes is a squamous epithelial cells that lined the terminal sacs and this is the place where the gas exchange take place. Type II pneumocytes is a secretory epithelial cells that secrete surfactant and distributed among the type I pneumocytes.
Available at http://basenat.u707.jussieu.fr/site_respirare/index.php?option=com_content&view=article&id=59&Itemid=30&lang=en&limit
Alveolar period
(32 weeks to 8 years)
In the uterus, the gas exchange performed by the placenta and as the baby is delivered, he/she has to use the lungs to breath. In order to do that, the lungs have to be prepared by getting sufficient number of mature alveoli that produce surfactant. The lung development is stimulated by the fetal breathing movements which cause aspiration of amniotic fluid. At birth when the baby use the lungs to breath, the lung fluid is reabsorbed by the capillaries and the lymphatic vessels. Some of it is expelled by the trachea and the bronchi during delivery. After the baby is born, the lung alveoli will expand and increase in sizes and this process is completed after the baby reach 3 years old. New alveoli may created until the age of 10 years old.
(32 weeks to 8 years)
In the uterus, the gas exchange performed by the placenta and as the baby is delivered, he/she has to use the lungs to breath. In order to do that, the lungs have to be prepared by getting sufficient number of mature alveoli that produce surfactant. The lung development is stimulated by the fetal breathing movements which cause aspiration of amniotic fluid. At birth when the baby use the lungs to breath, the lung fluid is reabsorbed by the capillaries and the lymphatic vessels. Some of it is expelled by the trachea and the bronchi during delivery. After the baby is born, the lung alveoli will expand and increase in sizes and this process is completed after the baby reach 3 years old. New alveoli may created until the age of 10 years old.
Available at http://basenat.u707.jussieu.fr/site_respirare/index.php?option=com_content&view=article&id=59&Itemid=30&lang=en&limit