Respiratory and Digestive

Respiratory and Digestive

1. body folding

   • creates gut tube
     • suspended by dorsal mesentery
       • from posterior body wall
       • forms greater omentum
         • protects from infections
     • organ buds
       • will be covered by visceral dorsal mesentery
     • around connecting stalk
     • four gut regions
       • differentiated by different genes
         • pharyngeal
         • foregut
           • proliferates
             • respiratory diverticulum
               • grows two lungs
                 • branching in lung buds
                   • cartilage
                     • keeps branches from collapse
                   • type 1 alveolar cells
                     • gas exchange
                     • big surface area, thin membrane
                       • more oxgenation
                   • 16-26 weeks
                   • type 2 alveolar cells
                     • secrete soapy surfactant
                       • decrease surface tension
                         • prevent collapse of alveoli
               • have to close from esophagus
                 • tracheoesophageal ridge
                   • forms septum to separate trachea and esophagus
                     • visceral mesoderm makes cartilage
                 • abnormalities
                   • tracheoesophageal fistula and atresias
             • liver bud
               • growth causes thinning of septum transversum
                 • forms
                   • falciform ligament
                   • lesser omentum
                 • 5 weeks
             • gall bladder
             • pancreas
               • fusion
                 • dorsal bud
                 • ventral bud
                 • 7 weeks
         • midgut
           • primary intestinal loop
             • 6 weeks
             • physiological umbilical herniation
               • because there is not enough room
                 • omphalocele
                   • failure of gut to return to peritoneal cavity
               • 8 weeks
         • hindgut
           • urorectal septum
             • separates hindgut from cloaca
               • 5 weeks
               • abnormalities
                 • when septum doesn't grow down far enough
                   • urorectal fistula
                   • rectovaginal fistula
                   • imperforate anus
     • ventral mesentery
       • forms from septum transversum
       • only covers esophagus to liver bud
       • lesser omentum
       • falciform ligament

2. yolk sac

   • initial region
     • making blood cells
     • holding germ cells
   • attached to midgut
     • by vitelline duct
       • defects
         • Meckel's diverticulum
         • vitelline cyst
         • vitelline fistula