The structure of the alimentary canal

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The alimentary canal is made up of mucosa demarcated by the muscularis mucosae from the submucosa, the muscle coat and the serosa — the last being absent where the gut is extraperitoneal.

Middle colic artery Superior mesenteric artery

Right colic artery

Ileocolic artery Superior

Jejunal and ileal branches rectal artery

Middle colic artery Superior mesenteric artery

Right colic artery

Ileocolic artery Superior

Jejunal and ileal branches rectal artery

Ileocolic Artery

_ Inferior mesenteric

Terminal colic node artery

Left colic artery Sigmoid branches

Fig. 68 Lymph nodes of the large intestine.

_Paracolic node

_ Inferior mesenteric

Terminal colic node artery

Left colic artery Sigmoid branches

Fig. 68 Lymph nodes of the large intestine.

The oesophageal mucosa and that of the lower anal canal is stratified squamous; elsewhere it is columnar. At the cardio-oesophageal junction this transition is quite sharp, although occasionally columnar epithelium may line the lower oesophagus.

The gastric mucosa bears simple crypt-like glands projecting down to the muscularis mucosae. The pyloric antrum secretes an alkaline juice containing mucus and the hormone gastrin. The body of the stomach secretes pepsin and also HCl, the latter from the oxyntic cells lying sandwiched deeply between the surface cells. The stomach mucosa also produces intrinsic factor.

The mucosa of the duodenum and small intestine, as well as bearing crypt-like glands, projects into the bowel lumen in villous processes which greatly increase its surface area. The duodenum is distinguished by its crypts extending deep through the muscularis mucosae and opening into an extensive system of acini in the submucosa termed Brunner's glands.

The mucosa of the large intestine is lined almost entirely by mucus-secreting goblet cells; there are no villi.

The muscle coat of the alimentary tract is made up of an inner circular layer and an outer longitudinal layer. In the upper two-thirds of the oesophagus and at the anal margin this muscle is voluntary; elsewhere it is involuntary. The stomach wall is reinforced by an innermost oblique coat of muscle and the colon is characterized by the condensation of its longitudinal layer into three taeniae coli.

The autonomic nerve plexuses of Meissner and Auerbach lie respectively in the submucosal layer and between the circular and longitudinal muscle coats.

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Responses

  • eric
    Which of the layer of the temiae coli reinforces the body of the Stomach?
    4 years ago

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