Midgut
Encyclopedia
The midgut is the portion of the embryo
from which most of the intestines 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.
, an unpaired branch of the aorta
. 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 for processing and detoxification, while lymphatic drainage carries fatty chyle to the cisterna chyli
. Autonomic innervation of the midgut is from the superior mesenteric plexus
.
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
from which most of the intestines develop. After it bends around the superior mesenteric artery
Superior mesenteric artery
In human anatomy, the superior mesenteric artery arises from the anterior surface of the abdominal aorta, just inferior to the origin of the celiac trunk, and supplies the intestine from the lower part of the duodenum through two-thirds of the transverse colon, as well as the pancreas.-Location...
, it is called the "midgut loop". It comprises the portion of the alimentary canal from the end of the foregut
Foregut
The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. At this point it is continuous with the midgut...
at the opening of the bile duct
Bile duct
A bile duct is any of a number of long tube-like structures that carry bile.Bile, required for the digestion of food, is excreted by the liver into passages that carry bile toward the hepatic duct, which joins with the cystic duct to form the common bile duct, which opens into the intestine.The...
to the hindgut
Hindgut
The hindgut is the posterior part of the alimentary canal. In mammals, it includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and rectum.-Blood flow:...
, about two-thirds of the way through the transverse colon.
Structures in the adult midgut
- DuodenumDuodenumThe duodenum is the first 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 anterior intestine or proximal intestine may be used instead of duodenum...
(distal half of 2nd part, 3rd and 4th parts) - JejunumJejunumThe jejunum is the middle 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 middle intestine or mid-gut may be used instead of jejunum.The jejunum lies between the duodenum...
- IleumIleumThe 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 be used instead of ileum.The ileum follows the duodenum...
- CecumCecumThe cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
- AppendixVermiform appendixThe appendix is a blind-ended tube connected to the cecum , from which it develops embryologically. The cecum is a pouchlike structure of the colon...
- Ascending colonAscending colonThe ascending colon is smaller in caliber than the cecum.It passes upward, from its commencement at the cecum, opposite the colic valve, to the under surface of the right lobe of the liver, on the right of the gall-bladder, where it is lodged in a shallow depression, the colic impression; here it...
- Hepatic flexureHepatic flexureHepatic flexure is the sharp bend between the ascending and the transverse colon. The right colic flexure is adjacent to the liver, and is therefore also known as the hepatic flexure. Thus, the left colic flexure is also known as the splenic flexure...
of colon. - Transverse colonTransverse colonThe transverse colon, the longest and most movable part of the colon, passes with a downward convexity from the right hypochondrium region across the abdomen, opposite the confines of the epigastric and umbilical zones, into the left hypochondrium region, where it curves sharply on itself beneath...
(proximal two-thirds)
Vascular, lymphatics and innervation
Arterial supply to the midgut is from the superior mesenteric arterySuperior mesenteric artery
In human anatomy, the superior mesenteric artery arises from the anterior surface of the abdominal aorta, just inferior to the origin of the celiac trunk, and supplies the intestine from the lower part of the duodenum through two-thirds of the transverse colon, as well as the pancreas.-Location...
, an unpaired branch of the aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
. Venous drainage is to the portal venous system
Portal venous system
In human anatomy, the hepatic portal system is the system of veins comprising the hepatic portal vein and its tributaries. It is also called the portal venous system, although it is not the only example of a portal venous system, and splanchnic veins, which is not synonymous with hepatic portal...
. 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 for processing and detoxification, while lymphatic drainage carries fatty chyle to the cisterna chyli
Cisterna chyli
The cisterna chyli is a dilated sac at the lower end of the thoracic duct into which lymph from the intestinal trunk and two lumbar lymphatic trunks flow.-Flow of lymph:...
. Autonomic innervation of the midgut is from the superior mesenteric plexus
Superior mesenteric plexus
The superior mesenteric plexus is a continuation of the lower part of the celiac plexus, receiving a branch from the junction of the right vagus nerve with the plexus....
.
Clinical notes
- Malrotation of the midgut during development can lead to volvulusVolvulusA volvulus is a bowel obstruction with a loop of bowel whose nose has abnormally twisted on itself.-Types:* Volvulus Neonatorum.* Volvulus Small Intestine.* Volvulus Caecum.* Volvulus Sigmoid Colon .* Gastric volvulus....
. - Pain in the midgut is referred to the umbilical region (around the umbilicus (belly button)).