title: The growth pattern of the human intestine and its mesentery.
abstract: BACKGROUND
  It remains unclear to what extent midgut rotation determines human intestinal topography and pathology. We reinvestigated the midgut during its looping and herniation phases of development, using novel 3D visualization techniques.
  
  
  RESULTS
  We distinguished 3 generations of midgut loops. The topography of primary and secondary loops was constant, but that of tertiary loops not. The orientation of the primary loop changed from sagittal to transverse due to the descent of ventral structures in a body with a still helical body axis. The 1st secondary loop (duodenum, proximal jejunum) developed intraabdominally towards a left-sided position. The 2nd secondary loop (distal jejunum) assumed a left-sided position inside the hernia before returning, while the 3rd and 4th secondary loops retained near-midline positions. Intestinal return into the abdomen resembled a backward sliding movement. Only after return, the 4th secondary loop (distal ileum, cecum) rapidly "slid" into the right lower abdomen. The seemingly random position of the tertiary small-intestinal loops may have a biomechanical origin.
  
  
  CONCLUSIONS
  The interpretation of "intestinal rotation" as a mechanistic rather than a descriptive concept underlies much of the confusion accompanying the physiological herniation. We argue, instead, that the concept of "en-bloc rotation" of the developing midgut is a fallacy of schematic drawings. Primary, secondary and tertiary loops arise in a hierarchical fashion. The predictable position and growth of secondary loops is pre-patterned and determines adult intestinal topography. We hypothesize based on published accounts that malrotations result from stunted development of secondary loops.
authors: Department of Anatomy & Embryology, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. Jelly.soffers@maastrichtuniversity.nl.
authors: Jelly H M
authors: JH
authors: Soffers
authors: Department of Anatomy & Embryology, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. Jill.hikspoors@maastrichtuniversity.nl.
authors: Jill P J M
authors: JP
authors: Hikspoors
authors: Department of Anatomy & Embryology, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. Hayelom.mekonen@maastrichtuniversity.nl.
authors: Hayelom K
authors: HK
authors: Mekonen
authors: Department of Anatomy & Embryology, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. Leo.koehler@maastrichtuniveristy.nl.
authors: S Eleonore
authors: SE
authors: Koehler
authors: Department of Anatomy & Embryology, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. WH.Lamers@maastrichtuniversity.nl.|Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. WH.Lamers@maastrichtuniversity.nl.
authors: Wouter H
authors: WH
authors: Lamers
mesh_terms: D004622:Embryo, Mammalian / Q000033:anatomy & histology; D005333:Fetus / Q000033:anatomy & histology; D046449:Hernia, Abdominal / Q000473:pathology; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007422:Intestines / Q000033:anatomy & histology / Q000196:embryology*; D008643:Mesentery / Q000196:embryology*; D038081:Organogenesis