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  <head>
    <title>086-02 Gastrointestinal, urogenital, diaphragmatic, and musculoskeletal organogenesis</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Gut, urogenital, diaphragm, and musculoskeletal organogenesis">
      <outline text="Principles and gut germ layers">
        <outline text="Epithelial-mesenchymal interaction, ducts, rotations"/>
        <outline text="Identify tube, fusion plane, route, remodelling step"/>
        <outline text="Folding forms foregut, midgut, hindgut"/>
        <outline text="Endoderm: epithelium and glandular parenchyma"/>
        <outline text="Splanchnic mesoderm: muscle, stroma, vessels"/>
        <outline text="Neural crest: enteric ganglia"/>
      </outline>
      <outline text="Foregut: oesophagus, stomach, duodenum">
        <outline text="Oesophagus lengthens as heart and lungs descend">
          <outline text="Partition error: fistula or atresia"/>
          <outline text="Failed recanalisation: stenosis"/>
        </outline>
        <outline text="Faster dorsal wall forms greater curvature"/>
        <outline text="Longitudinal rotation: left side anterior">
          <outline text="Explains vagal trunk positions"/>
        </outline>
        <outline text="Pylorus moves up and to the right"/>
        <outline text="Dorsal mesogastrium: greater omentum, spleen"/>
        <outline text="Duodenum C-shaped, secondarily retroperitoneal">
          <outline text="Failed recanalisation: stenosis or atresia"/>
          <outline text="Bile-duct level changes vomiting"/>
        </outline>
      </outline>
      <outline text="Liver, biliary tree, and pancreas">
        <outline text="Liver bud grows into septum transversum">
          <outline text="Endoderm: hepatocytes, biliary epithelium"/>
          <outline text="Mesoderm: stroma, sinusoids, haematopoiesis"/>
        </outline>
        <outline text="Duct remodelling errors: atresia, cystic dilation"/>
        <outline text="Dorsal and ventral pancreatic buds">
          <outline text="Duodenal rotation brings ventral bud to fuse"/>
          <outline text="Ventral bud: uncinate process, part of head"/>
        </outline>
        <outline text="Fusion failure: pancreas divisum"/>
        <outline text="Bifid ventral tissue: annular pancreas"/>
      </outline>
      <outline text="Midgut rotation and body wall">
        <outline text="Vitelline duct links midgut to yolk sac"/>
        <outline text="Physiological herniation into umbilical cord"/>
        <outline text="About 270 degrees around superior mesenteric artery">
          <outline text="Ninety while herniated, 180 on return"/>
        </outline>
        <outline text="Caudal limb: distal ileum to transverse colon"/>
        <outline text="Caecum descends from subhepatic position"/>
        <outline text="Malrotation: abnormal mesenteric base">
          <outline text="Volvulus or obstructing bands"/>
        </outline>
        <outline text="Vitelline remnants: ileal diverticulum, fistula">
          <outline text="Ectopic gastric tissue may bleed"/>
        </outline>
        <outline text="Omphalocele: failed return, membrane-covered"/>
        <outline text="Gastroschisis: paraumbilical, uncovered bowel"/>
      </outline>
      <outline text="Hindgut, cloaca, and anal canal">
        <outline text="Urorectal septum divides cloaca">
          <outline text="Anorectal canal and urogenital sinus"/>
          <outline text="Partition errors: malformations and fistulas"/>
        </outline>
        <outline text="Pectinate line: endoderm above, ectoderm below">
          <outline text="Inferior mesenteric versus internal iliac supply"/>
        </outline>
        <outline text="Failed crest migration: distal aganglionic bowel">
          <outline text="Functional obstruction, proximal dilation"/>
        </outline>
      </outline>
      <outline text="Diaphragm">
        <outline text="Septum transversum and pleuroperitoneal membranes"/>
        <outline text="Oesophageal mesentery and body-wall muscle"/>
        <outline text="Phrenic supply follows cervical myoblasts"/>
        <outline text="Posterolateral defect: viscera enter thorax">
          <outline text="Impairs lung development"/>
        </outline>
      </outline>
      <outline text="Kidney and bladder">
        <outline text="Pronephros, mesonephros, metanephros"/>
        <outline text="Ureteric bud invades metanephric mesenchyme">
          <outline text="Bud: ureter, pelvis, calyces, collecting ducts"/>
          <outline text="Mesenchyme: nephrons to distal tubule"/>
          <outline text="Failed induction: renal agenesis"/>
        </outline>
        <outline text="Apparent ascent and medial hilar rotation">
          <outline text="Successive arterial branches from aorta"/>
          <outline text="Horseshoe kidney arrested beneath IMA"/>
        </outline>
        <outline text="Trigone incorporates mesonephric-duct tissue"/>
        <outline text="Urachal remnants: fistula, sinus, cyst"/>
      </outline>
      <outline text="Genital development">
        <outline text="Indifferent gonad and primordial germ cells"/>
        <outline text="Sertoli anti-Müllerian hormone regresses ducts"/>
        <outline text="Leydig testosterone, local dihydrotestosterone"/>
        <outline text="No testis signal: paramesonephric ducts persist">
          <outline text="Uterine tubes, uterus, upper vagina"/>
          <outline text="Fusion errors: bicornuate or septate uterus"/>
        </outline>
        <outline text="Incomplete urethral-fold fusion: hypospadias"/>
      </outline>
      <outline text="Axial skeleton and limbs">
        <outline text="Sclerotomes resegment into vertebrae"/>
        <outline text="Myotomes split into epaxial and hypaxial"/>
        <outline text="Apical ectodermal ridge: proximodistal growth"/>
        <outline text="Zone of polarising activity: digit axis"/>
        <outline text="Upper limb rotates laterally, lower medially"/>
        <outline text="Programmed cell death separates digits"/>
      </outline>
    </outline>
  </body>
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