Extend and derivative of foregut hindgut and midgut
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Derivatives of Foregut, Midgut, and Hindgut
The primordial gut forms during the 4th week from the endoderm-lined cavity enclosed by the embryonic folding process. It extends from the oropharyngeal membrane to the cloacal membrane and is divided into three regions based on blood supply and developmental origin.
FOREGUT
Artery of supply: Celiac trunk (celiac artery)
Derivatives:
| Structure | Details |
|---|---|
| Primordial pharynx | Gives rise to the oral cavity, pharynx, tongue, tonsils, salivary glands, and thyroid/parathyroid glands |
| Lower respiratory system | Larynx, trachea, bronchi, and lungs (from respiratory diverticulum/lung bud at ~4 weeks) |
| Esophagus | Develops immediately caudal to the pharynx; partitioned from trachea by the tracheoesophageal septum |
| Stomach | Rotates 90° clockwise during development |
| Duodenum (proximal part) | Up to and including the opening of the bile duct (hepatopancreatic ampulla) |
| Liver | From the hepatic diverticulum (ventral bud of foregut endoderm) |
| Biliary apparatus | Hepatic ducts, gallbladder, and bile duct |
| Pancreas | From dorsal and ventral pancreatic buds of the foregut; ventral bud rotates to fuse with dorsal bud |
Note: The pharynx, lower respiratory tract, and most of the esophagus are supplied by branches of the aorta (not celiac trunk directly), but are still foregut derivatives. The abdominal foregut derivatives (stomach through pancreas) are supplied by the celiac trunk.
- The Developing Human, Clinically Oriented Embryology, p. 604
MIDGUT
Artery of supply: Superior mesenteric artery (SMA)
Derivatives:
| Structure | Details |
|---|---|
| Duodenum (distal part) | Distal to the opening of the bile duct |
| Jejunum | - |
| Ileum | - |
| Cecum | - |
| Appendix | - |
| Ascending colon | - |
| Transverse colon (right 1/2 to 2/3) | The right to middle portion; exact junction varies |
Key developmental event - Physiologic umbilical herniation:
- At ~6 weeks, the rapidly elongating midgut herniates into the umbilical cord as a U-shaped loop (midgut loop)
- The loop undergoes 270° counterclockwise rotation around the SMA axis (in three 90° stages)
- Returns to the abdomen at ~10 weeks
- Failure of return = omphalocele; failure of rotation = malrotation
- The Developing Human, Clinically Oriented Embryology, p. 632
HINDGUT
Artery of supply: Inferior mesenteric artery (IMA)
Derivatives:
| Structure | Details |
|---|---|
| Transverse colon (left 1/3 to 1/2) | Distal portion, where SMA supply ends and IMA begins |
| Descending colon | Becomes retroperitoneal as its mesentery fuses with parietal peritoneum |
| Sigmoid colon | Retains its mesentery |
| Rectum | - |
| Superior 2/3 of anal canal | Endoderm-derived; above the pectinate line |
| Epithelium of urinary bladder | From subdivision of the cloaca |
| Most of the urethra | From the urogenital sinus (ventral division of cloaca) |
The Cloaca and its partitioning:
- The terminal hindgut expands into the cloaca, which receives the allantois ventrally
- A wedge of mesenchyme called the urorectal septum grows between the allantois and hindgut
- This divides the cloaca into:
- Dorsal part: rectum and upper anal canal
- Ventral part: urogenital sinus (gives rise to bladder and urethra)
- The inferior 1/3 of the anal canal is derived from the anal pit (proctodeum) - ectoderm-lined, supplied by inferior rectal branches of the internal pudendal artery
- The pectinate line marks the junction between endodermal hindgut epithelium (above) and ectodermal anal pit epithelium (below)
- The Developing Human, Clinically Oriented Embryology, p. 653-655
SUMMARY TABLE
| Region | Artery | Derivatives |
|---|---|---|
| Foregut | Celiac trunk | Pharynx, lower respiratory tract, esophagus, stomach, proximal duodenum (to bile duct opening), liver, gallbladder, bile ducts, pancreas |
| Midgut | Superior mesenteric artery | Distal duodenum, jejunum, ileum, cecum, appendix, ascending colon, right 1/2-2/3 of transverse colon |
| Hindgut | Inferior mesenteric artery | Left 1/3-1/2 of transverse colon, descending colon, sigmoid colon, rectum, upper 2/3 anal canal, bladder epithelium, most of urethra |
NERVE SUPPLY (Autonomic)
- Foregut: Vagus nerve (CN X) - parasympathetic; celiac plexus - sympathetic
- Midgut: Vagus nerve (CN X) - parasympathetic (up to approximately the left colic flexure); superior mesenteric plexus - sympathetic
- Hindgut: Pelvic splanchnic nerves (S2-S4) - parasympathetic; inferior mesenteric plexus - sympathetic
The referred pain from foregut structures (stomach, duodenum, liver, pancreas) is felt in the epigastric region; midgut pain is felt periumbilically; hindgut pain is felt in the hypogastric/suprapubic region - a clinically useful pattern reflecting the embryonic innervation.
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