Development of digestive system and respiratory system

1. Primitive gut

2. Development of primary pharynx

3. Development of esophagus and stomach

4. Intestinal development

5. Development of liver, gall bladder and pancreas

6. 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

HindgutAllantois

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

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

12

3

4

5

External acoustic meatus

thymus

superior parathyroid

gland

inferior parathyroid

gland

thyroid

Palatine tonsil

tympanic membrane

pharyngotympanic tube

tympanic cavity

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

②simple → stratified

①prolong

③reconstitution of lumen

　 Development of stomach

a dilation at the end of foregut

Dorsal convex left

Ventral concave right

Dorsal mesogastrium

RightVentral

mesogastrium Left

Liver

End

Head

Duodenum

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

Anorectal canal

Urogenital sinusUrogenital membrane Anal membrane

Development of liver, gall bladder and pancreas

Time 4th week

End of foregut Hepatic diverticulum

Head

Tail

Hepatic cord

Gall bladder

Mesenchyme Stroma,

Capsule

Process

1. Development of liver, 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

End of foregutEnd of foregut

4th week

Dorsal parentic bud

Ventral parentic bud

Left

Right

Fusion

Rotation

Pancreas

Above of hepatic diverticulum

Under hepatic diverticulum

Dorsal

pancreas

Ventral pancreas

但怪但

Head of hepatic diverticulum

End of hepatic diverticulum

Dorsal pancreatic

bud

Ventral pancreatic bud

碱

Dorsal pancreas

Ventral pancreas

Liver

Gall bladder

Dorsal pancreas

Ventral pancreas

Ventral pancreas

Dorsal pancreas

Main pancreatic

duct

Accessory

pancreatic ductDuodenum

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

Development of larynx, trachea and lung

Primitive pharynx

4th week

Longitudinal

depression

Laryngotracheal groove

Laryngotracheal divertuculum Right lung

bud

Left lung bud

Tracheoesophageal septum

Laryngotracheal groove

End of 4th week: lung buds

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

Pulmonary alveoli

StromaMesenchyme

Lung bud

LengthenBronchia and

their branches

Abnormality of respiratory system

• Tracheoesophageal fistula