Gastrointestinal system
From IKE
The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which ingests, digests, and egests food, and in the process, extracts energy and nutrients. (1)
Contents |
Development
Folding
Due to folding, endoderm lining the yolk sac is incorporated into the embryo as the primitive gut tube. Initially, the midgut maintains a connection with the yolk sac via the yolk stalk (vitelline duct), but later, both the yolk sac and the vitelline duct usually disappear. The mesentery helps keep everything in place.
Derivatives and blood supply
The table below is a summary of the derivatives (and arterial supply) of the caudal foregut, midgut and hindgut.
| Gut | Derivatives | Artery | |
| Foregut | proximal | oral cavity, pharynx, upper esophagus, respiratory tract | Various |
| distal | lower esophagus, stomach, small intestine (prox. 1/2 duodenum) liver, gall bladder, pancreas | coeliac | |
| Midgut | small intestine (distal 1/2 duodenum, jejunum, ileum), large intestine (caecum, appendix, ascending colon, prox. 2/3 transverse colon) | superior mesenteric | |
| Hindgut | large intestine (distal a transverse colon, descending colon, sigmoid colon, rectum, anal canal) | inferior mesenteric | |
Histology
Layers
The gastrointestinal tract has several main layers, which are common to the various parts:
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa/Adventitia
For more in-depth histology, see:
Resources
- Development of the GI system lecture (notes, diagrams)
- Slides for Histology of the Esophagus, stomach, liver, pancreas and intestine (PPT)
- Dissection instructions for GI and GU labs (PDF)
