Anatomy · Organs & viscera

Caecum

First part of the large intestine

Abdomen · right iliac fossa

The caecum is the blind-ended pouch that forms the first part of the large intestine, sitting low in the right iliac fossa below the point where the ileum enters. The ileocaecal valve guards the entry from the small bowel, and the appendix hangs from its lower end. It is the widest part of the large bowel and the most distensible.

How to spot them

▸A wide pouch in the right iliac fossa, below the level of the ileocaecal junction, continuous above with the ascending colon
▸The ileum enters its medial side through the ileocaecal valve
▸The worm-like appendix arises from its posteromedial wall, a couple of centimetres below that valve
▸The three taeniae coli begin at the base of the appendix and run up the colon

What to know

A blind-ended pouch about 6 cm long in the right iliac fossa, hanging below the entry of the small bowel

Caecum — from the Latin caecus, 'blind'.

A two-lipped valve where the last part of the small bowel opens into the large, preventing backflow

The ileocaecal valve, opening into the caecum on its medial side.

The part of the large bowel that gives origin to a narrow worm-like tube from its posteromedial wall

The caecum, bearing the vermiform appendix.

The widest and thinnest-walled part of the large bowel, first to perforate when the bowel downstream is blocked

Caecum — the Law of Laplace makes it burst first in large-bowel obstruction.

Fed by an artery branch of the ileocolic artery, and often lacking any fixed attachment to the back wall, so it may twist

A mobile caecum can twist in a caecal volvulus.

Sits on iliacus and psoas major and is covered by peritoneum, with a retrocaecal recess behind it

The caecum, in the right iliac fossa.

Key ideas

In herbivores such as rabbits and horses the caecum is huge and acts as a fermentation chamber for cellulose. In humans it is small and the appendix is its vestige.
The caecum and ascending colon mix and absorb fluid from the liquid chyme that squirts through the ileocaecal valve.

Quick-fire facts

•The word caecum is Latin for 'blind', because the pouch ends blindly below the entry of the ileum.
•The caecum is roughly 6 cm long and about as wide, the widest part of the large intestine.
•The ileocaecal valve, sometimes called Bauhin's valve, opens on its posteromedial wall.
•The appendix arises about 2 cm below the ileocaecal valve where the three taeniae coli meet.
•The caecum is usually completely covered in peritoneum, but has little or no mesentery in most people, so it is fairly mobile.
•Blood comes from the ileocolic artery, a branch of the superior mesenteric artery, via anterior and posterior caecal branches.
•Its position in the right iliac fossa makes it a landmark in surgery and in the classic right iliac fossa pain of appendicitis.
•In American spelling it is the cecum; British English keeps the ae.

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Sources

OpenStax — The Small and Large Intestines (Anatomy and Physiology 2e, section 23.5)
TeachMeAnatomy — The Appendix