Midgut
From IKE
The midgut is the middle part of the alimentary canal, from the stomach (or entrance of the bile duct) to, or including, the large intestine (1)
Development
- The midgut undergoes rapid elongation during the 5th week of development
- This results in a primary midgut loop, with the vitelline duct at its apex
- The vitelline duct acts as a landmark, dividing the loop into a proximal (cranial) and a distal (caudal) limb
- the midgut loop "herniates" into the body stalk (umbilical cord) due to its rapid growth
- At this stage, growth of the proximal limb outpaces that of the distal limb
- During herniation, the midgut loop rotates 90° counter-clockwise (viewed from the ventral [anterior] aspect)
- The future caecum appears as a sacculation in the distal limb
- At about the 10th week, the midgut begins to return to the peritoneal cavity
- By this time, the vitelline duct has usually disappeared, so that the apex of the loop is no longer connected to the body stalk
- The proximal limb, consisting of coils of jejunum and ileum, is the first to return, followed by the distal limb, with the caecum entering last
- As it re-enters, the midgut rotates another 180° counter-clockwise (270° in total)
- With further growth, the cecum migrates inferiorly to its final destination in the lower right quadrant of the peritoneal cavity, while the ascending colon occupies the right side of the cavity
- At this stage, the appendix has developed as a small blind-ending diverticulum of the caecum.
