Corpus: Cecum

The caecum or appendix is the most proximal section of the large intestine. The ileum (part of the small intestine) opens into the caecum via the Bauhin valve, as does the vermiform appendix (appendix vermiformis) via the Gerlach valve.

Colloquially, the vermiform appendix is incorrectly referred to as the "appendix".

The caecum is located in the lower right part of the abdominal cavity. It is the sac-shaped protuberant initial part of the ascending colon, which forms a side bay of the actual intestinal canal and ends blindly. With a diameter of around 7 cm, the caecum is the widest section of the entire large intestine. Its caudal end lies approximately at the level of McBurney's point.

The lower end of the ileum protrudes into the cecum, forming the Bauhin valve (ileocecal valve). It forms a barrier against the ascension of bacteria into the largely germ-free small intestine.

The caecum contains abundant lymphoid tissue of the GALT in its wall and therefore plays an important role in mediating immunity processes against antigens that are absorbed via the digestive tract.

Peritoneal conditions[Bearbeiten]

As a rule, the caecum is located intraperitoneally, although the peritoneal ratios are variable. A distinction is made between:

• Caecum fixum: The caecum is located secondarily retroperitoneally
• Caecum mobile: The caecum has a weakly developed mesentery (mesocaecum), which is accompanied by a strong mobility with a tendency to constipation.
• Caecum liberum: A mesocaecum is fully developed, the caecum is intraperitoneal.

Arterial supply[Bearbeiten]

The caecum is supplied with arterial blood via the anterior caecal artery and the posterior caecal artery from the ileocolic artery.

The caecum - like the neighbouring colon - shows the typical stratification of the digestive tract in

• Mucosa,
• submucosa,
• tunica muscularis and
• serosa (in the intraperitoneal position) or adventitia (in the retroperitoneal position)

The circular muscle layer (stratum circulare) is continuous, the longitudinal muscle layer (stratum longitudinale) is interrupted and concentrated in the form of ligamentous tenae. The mucosa has crypts but, unlike the small intestine, no villi. It has numerous goblet cells. Lymph follicles are found in the tela submucosa.

In herbivores, the caecum is longer than in carnivores. It may be completely absent in pure carnivores. The caecum therefore appears to play a role in the digestion of fibre-rich food components. It also serves as a reservoir for bacterial colonisation of the large intestine. Its lymphatic tissue makes it an important part of the gastrointestinal immune system.

• Image source for podcast: © Amelia Speight / Unsplash