29. Large intestine. Embryonic development. Parts. Caecum and colon. Vermiform appendix Macro-scopic, microscopic, ultramicroscopic and functional characteristics. Blood and nerve supply.

65 LARGE INTESTINE

• The last part of the digestive System.
• Extends from the distal end of the ileum to the anus
• Length ~ 1.5 m
• Function:

Innervation:

1. Sup. Mesenteric plexus → cecum, appendix, ascen. colon & transverse colon
2. Inf. Mesenteric plexus → from left colic flexure to the rectum.

Blood supply:

1. Superior mesenteric art. (SMA)
2. Inferior mesenteric art. (IMA)

Parts.

1. Caecum
2. 1.1 Vermiform appendix (appendix vermiformis)
3. Colon
4. 2.1 Ascending colon (colon ascendens)
5. 2.2 Transverse colon (colon transversum)
6. 2.3 Descending colon (colon descendens)
7. 2.4 Sigmoid colon (colon sigmoideum)
8. Rectum
9. 3.1 Anus

Histology:

Mucosa (and submucosa)

• contains a single layer of columnar epithelium, there are no villi

Muscular layer – has a circular and a longitudinal layer of smooth muscle

• there are several regions along the course of the large intestine with highly developed circular muscle that form functional sphincters

Superficial layer – is covered by the visceral peritoneum except on the posterior wall of the ascending and descending colon and the aboral part of the rectum, which are connected to the surrounding tissue by adventitia