1. Formation of the human digestive system, depicted at about (A) 16 days, (B) 18 days, (C) 22 days, and (D) 28 days. Digestive System Alimentary Canal develops from endoderm and splanchnic mesoderm

2. 15.24 Formation of the human digestive system (Part 1)

3. 15.24 Formation of the human digestive system (Part 2)

4. Epi Ecto invaginates to meet endo to form Stomodeum & Proctodeum A septum separates the cloaca into anus (dorsal) and urogenital (ventral

5. Branchial Apparatus: the pharynx forms cavity within arches. Arch (mesoderm), Groove (epi ecto), Pouch (endo)

6. 15.25 Formation of glandular primordia from the pharyngeal pouches (Part 1) Branchial Apparatus Arch (mesoderm), Groove (epi ecto), Pouch (endo) The fate of the pharyngeal pouches: 1st forms the external auditory passages

7. 15.24 Formation of the human digestive system (Part 3)

8. Digestive System Alimentary Canal develops from endoderm and splanchnic mesoderm four layers of the digestive tract - the mucosa (1), the submucosa (2), the muscularis (3), the serosa (4). Peritoneum - visceral vs parietal Mesentery )

9. Alimentary Canal and Association Organs Differentiation of associated organs at the level of the forming stomach occurs both dorsally (spleen) and ventrally (liver).

10. 15.26 Regional specification of the gut endoderm and splanchnic mesoderm through reciprocal interactions (Part 1)

11. 15.27 Pancreatic development in humans (Part 1)

13. 15.30 Partitioning of the foregut into the esophagus and respiratory diverticulum during the third and fourth weeks of human gestation

14. 15.31 Ability of presumptive lung epithelium to differentiate with respect to the source of the inducing mesenchyme

15. respiratory system not gas exchange source until after birth late in fetal development ventilation with amniotic fluid - role in lung maturation. Fetal Respiratory Distress Syndrome - insufficient surfactant (end month alveolar cells secrete surfactant). respiratory tract and aveolar epithelium are endoderm in origin with mesoderm contributing surrounding tissue

16. 15.32 The immune system relays a signal from the embryonic lung