Производные энтодермы

латеральный вид и фронтальный срез

Каждая жаберная дуга состоит из эктодермального зпидермиса (зеленый) и внутренней энтодермальной выстилки (синий). Врастания энтодермы, направленные в жаберные щели сторону эпидермиса (стрелки) формируют тимус, щитовидные и паращитовидние железы.
Между эктодермой и энтодермой расположены структуры, происходящие из клеток нервного гребня (красный), которые формируют потом лицевой скелет и соединительную ткань. Мезодермальные клетки (желтый) формируют мускулатуру глотки и участвуют в формировании артерий этой области

Week 5 - left and right lung buds push into the pericardioperitoneal canals (primordia of pleural cavity)
Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes.
Week 7 - enlargement of liver stops descent of heart and lungs.
Month 3-6 - lungs appear glandular, end month 6 alveolar cells type 2 appear and begin to secrete surfactant.
Month 7 - respiratory bronchioles proliferate and end in alveolar ducts and sacs.

4 периода формирования легких:
5-17 нед. - псевдогранулярный
16-25 нед. – канальцевый (canalicular)
24-40 нед. - terminal sac
Поздний фетальный и до 8 лет - альвеолярный

developing lung

Reciprocal FGF signaling between epithelium and mesenchyme
during
lung (top) and
limb (bottom) embryogenesis.

Signaling during proximal airway branching in the early pseudoglandular period

Signaling during airway branching in the late pseudoglandular period.

Signaling during development of distal airspaces. Mesenchyme surrounding epithelial buds is sharply reduced; focally high Fgf10 expression in the adjacent mesenchyme is lost; and epithelial differentiation begins with the narrowing of the epithelium.

pancreas

The visceral organs of the thorax and abdomen develop asymmetrically on the left and right hand sides of the body cavity. 
For example, the liver develops predominantly on the right hand side while the spleen, stomach and heart develop to the left.  All organs originate along the midline of the embryo and are subsequently signalled as to which side to develop. 
Abnormalities in the normal development of laterality lead to discordant left-right placement of the internal organs giving rise to a number of classes of birth defects.  The most severe are congenital cardiac defects, but commonly organ isomerisms occur.  These include polysplenia, asplenia, and defects in gut looping. 
? Bapx1, which has localised affects on the 3-dimensional placement of the stomach, spleen and pancreas.  Bapx1 regulates the signalling from a novel embryonic organiser we have dubbed the SMP (splanchnic mesodermal plate) (Fig.5).  In collaboration with David Fitzpatrick we are analysing a gene responsible for the Matthew Wood Syndrome which effects heart asymmetry, lung hypoplasia and rudimentary spleen.  This gene is a membrane bound retinoic acid (RA) receptor.

www.hgu.mrc.ac.uk/Research/Hill/asymmetry.html