The midgut is the portion of the human embryo from which almost all of the

small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

and approximately half of the

large intestine The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the Digestion, digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces befor ...

develop. After it bends around the superior mesenteric artery, it is called the "midgut loop". It comprises the portion of the alimentary canal from the end of the foregut at the opening of the bile duct to the hindgut, about two-thirds of the way through the transverse colon. In addition to representing an important distinction in embryologic development, the tissues derived from the midgut additionally have distinct vascular supply and innervation patterns in the adult gastrointestinal system.

In the embryo

During standard human embryonic development, the midgut undergoes a process known as physiological herniation around week 6, when rapid growth forces the midgut to temporarily exit the abdominal cavity and reside in the extra-abdominal umbilical cord. At this stage, the midgut begins its initial counterclockwise rotation around the axis of the superior mesenteric artery (SMA). This rotation positions the cranial limb (destined to form parts of the small intestine) to the right and the caudal limb (which will give rise to parts of the colon) to the left. Between weeks 10 and 12, the midgut retracts back into the abdominal cavity (leaving the umbilicus), undergoing an additional counterclockwise rotation, culminating in a total rotation of 270 degrees. This repositioning aligns the intestinal segments in their proper anatomical locations—for instance, placing the duodenojejunal junction in the left upper quadrant and the

cecum The cecum ( caecum, ; plural ceca or caeca, ) is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix (a ...

in the right lower quadrant. Concurrently, the mesentery that supports the intestines becomes fixed to the posterior abdominal wall, ensuring proper stability and vascular supply; any disruptions in this intricate rotation and fixation process can lead to malrotation or other congenital anomalies.

In the adult

Organs in the adult midgut

* Duodenum ( distal half of 2nd part, 3rd and 4th parts) *

Jejunum The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been pr ...

Ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may ...

Cecum The cecum ( caecum, ; plural ceca or caeca, ) is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix (a ...

* Appendix * Ascending colon * Hepatic flexure of colon * Transverse colon ( proximal two-thirds)

Vascular, lymphatics and innervation

Arterial supply to the midgut is from the superior mesenteric artery, an unpaired branch of the

aorta The aorta ( ; : aortas or aortae) is the main and largest artery in the human body, originating from the Ventricle (heart), left ventricle of the heart, branching upwards immediately after, and extending down to the abdomen, where it splits at ...

. Venous drainage is to the portal venous system. Lymph from the midgut drains to prevertebral superior mesenteric nodes located at the origin of the superior mesenteric artery from the aorta. Portal drainage carries all non-lipid nutrients from digestion to the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

for processing and detoxification, while lymphatic drainage carries fatty chyle to the cisterna chyli. Parasympathetic innervation of the midgut is from the superior mesenteric plexus, while sympathetic innervation is from the lesser splanchnic nerve.

Clinical significance

* Malrotation of the midgut during development can lead to volvulus. * Pain in the midgut is referred to the region around the belly button As stated, in development a loop of midgut herniates outside of the abdominal cavity into the umbilical cord. If this persists after birth it is called an omphalocele. In omphalocele, there is a defect in the development of the anterior abdominal wall.

References

External links

* * – "Midgut Volvulus" *
Umich.edu – development
{{Authority control Embryology of digestive system