The Development of the Mesenteric Model of Abdominal Anatomy

Abstract

Recent advances in mesenteric anatomy have clarified the shape of the mesentery in adulthood. A key finding is the recognition of mesenteric continuity, which extends from the oesophagogastric junction to the mesorectal level. All abdominal digestive organs develop within, or on, the mesentery and in adulthood remain directly connected to the mesentery. Identification of mesenteric continuity has enabled division of the abdomen into two separate compartments. These are the mesenteric domain (upon which the abdominal digestive system is centered) and the non-mesenteric domain, which comprises the urogenital system, musculoskeletal frame, and great vessels. Given this anatomical endpoint differs significantly from conventional descriptions, a reappraisal of mesenteric developmental anatomy was recently performed. The following narrative review summarizes recent advances in abdominal embryology and mesenteric morphogenesis. It also examines the developmental basis for compartmentalizing the abdomen into two separate domains along mesenteric lines.

Keywords: abdomen; anatomy; embryology; mesentery; peritoneum.

Fig. 1

Three-dimensional reconstructions of developing human embryos depicting mesenteric anatomy. (A) Left lateral view of the mesentery developing at CS13. Indentation indicated in upper region. Foregut in red , midgut in green , and hindgut in blue . (B) Anterolateral view of the mesentery at CS16. Intramesenteric vasculature in red . Presence of mesenteric fold seen at SMA (superior mesenteric artery). (C) Development of the upper region of mesentery at CS16. Panel of images showing subtraction of various regions of the upper region to expose the neck of the bursa.

Fig. 2

Three-dimensional reconstructions demonstrating the abdominal digestive system developing on the mesentery. (A–D) Development of endoderm at CS13, CS16, CS23, and 10 weeks postconception. Mesentery in yellow , foregut in red , midgut in green , hindgut in blue , and vasculature in dark red . (E–H) Development of the pancreatic endoderm ( blue ) within the mesentery at CS 13 to 10 weeks postfertilization. (I–K) Development of the spleen ( pink ) at the lateral margin of the upper region of mesentery from CS16 to 10 weeks postfertilization.

Fig. 3

Three-dimensional reconstructions demonstrating relationship between the mesentery and intestine and the development of the intestine–mesenteric interface. (A, B) Anterior and posterior views of reconstruction of the mesentery at CS16. (C, D) Anterior and posterior views of reconstruction of the mesentery at CS23. (E, F) Anterior and posterior views of reconstruction of the mesentery at 12 weeks postfertilization. Intestine present at the periphery of the mesentery. (G) Panel of histological images shows the development of the interface between the intestine and mesentery. Endoderm in green , mesodermal mesentery in green , and mesodermal component of the intestine in blue .