Development of digestive system and respiratory system Primitive gut Development of primary pharynx Development of esophagus and stomach Intestinal development Development of liver, gall bladder and pancreas Development of larynx, trachea and lung

Primitive gut Primitive gut ：3rd～4th week Endoderm→ primitive gut buccopharyngeal membrane (breach at 4th week) → cloacal membrane (breach at 8th week) foregut, midgut and hindgut Vitelline stalk (atresia at 6th week)

Vitelline stalk Foregut Midgut Hindgut Allantois

Foregut Hindgut

Development of primary pharynx Primary pharynx：flattened funnel Pharyngeal pouch：5 pairs First： branchial membrane →tympanic membrane outer portion →tympanic cavity inner portion →pharyngotympanic tube

Second：outer portion → degeneration Third：ventral portion →thymus inner portion →tonsil Third：ventral portion →thymus dorsal portion → inferior parathyroid gland Fourth：ventral portion →degeneration dorsal portion → superior parathyroid gland Fifth：ultimobranchial body →parafollicular cell

1 2 3 4 5

External acoustic meatus pharyngotympanic tube tympanic cavity tympanic membrane External acoustic meatus thyroid Palatine tonsil superior parathyroid gland inferior parathyroid gland thymus

Development of esophagus and stomach 1. Esophagus：primitive gut between laryngotracheal diverticulum and stomach 2. Stomatch：a dilation at the end of foregut

Development of esophagus ①prolong ②simple → stratified ③reconstitution of lumen

Development of stomach a dilation at the end of foregut

Dorsal convex left Ventral concave right

Dorsal mesogastrium Ventral mesogastrium Left Right

Head Liver Duodenum End

Intestinal development 1. Evolvement of midgut ① Midgut loop： 5th week ② Physiological umblical herniation: 6th week ③ Counter-clockwise 90°rotation, caecal swelling 6th to 8th week ④ Counter-clockwise 180°rotation 10th week

A B C D

2. Evolvement of hindgut Compartmentation of cloaca: urorectal septum (6-7th week) Anorectal canal (dorsal) Cloaca Urogenital sinus (ventral) Anal membrane (dorsal) Cloacal membrane Urogenital membrane (ventral)

Urorectal septum Urogenital sinus Urogenital membrane Anal membrane Anorectal canal

Development of liver, gall bladder and pancreas Time 4th week Process Head Hepatic cord Stroma, Capsule Hepatic diverticulum End of foregut Mesenchyme Tail Gall bladder

Hepatic cord → Hepatic plate Vitelline vein and umbilical vein →Hepatic sinusoid Bile canaliculus: 6th week Hematopoietic stem cell: 6th week Hepatic lobule : 9-10th week

2. Development of pancreas Above of hepatic diverticulum 4th week Fusion Dorsal parentic bud Dorsal pancreas Left Pancreas End of foregut Rotation Ventral parentic bud Ventral pancreas Right Under hepatic diverticulum

但怪但 Head of hepatic diverticulum Dorsal pancreatic bud End of hepatic diverticulum 但怪但 Ventral pancreatic bud

碱 Liver Dorsal pancreas Gall bladder Ventral pancreas

Dorsal pancreas Ventral pancreas

Pancreas islet: function from 5th month Main pancreatic duct Ventral pancreas Dorsal pancreas Accessory pancreatic duct Duodenum Pancreas islet: function from 5th month

Abnormality of digestive system 1.Meckel’s diverticulum 2. Umbilical fistula　

３.Congenital umbilical hernia

4. Imperforate anus Rectum Anal pit Atresia

5.Congenital megacolon

Laryngotracheal groove Development of larynx, trachea and lung 4th week Laryngotracheal groove Primitive pharynx Longitudinal depression

Tracheoesophageal septum Left lung bud Laryngotracheal groove Laryngotracheal divertuculum Right lung bud

7th month: surfactant End of 4th week: lung buds 5th week: Left lung bud→ 2 branches 5th week: Right lung bud→ 3 branches Left lung bud→ 8-9 branches End of 2nd month: Right lung bud→ 10 branches End of 6th month: bronchia branch to alveoli 7th month: surfactant

Bronchia and their branches Lengthen Bronchia and their branches Pulmonary alveoli Lung bud Mesenchyme Stroma

Abnormality of respiratory system Tracheoesophageal fistula