What is the function of the rectum?

Waste materials move into the rectum, which is the final part of the large intestine, and are expelled from the body as a solid mass called stool. Inside the rectum, faeces remain in a semi-solid form until they are discharged through the anal canal during defecation.

Structure of the Rectum

• The rectum is the distal portion of the large intestine, functioning as a temporary storage site for faeces.
• It is continuous with the sigmoid colon at its upper end and terminates in the anal canal.
• It begins at the level of the S3 vertebra and is distinct from the colon as it lacks taenia coli, haustra, and omental appendages.
• The ampulla, its terminal section, relaxes to collect and hold faeces until elimination.

Nerve and Blood Supply

• Superior rectal artery: terminal branch of the inferior mesenteric artery.
• Middle rectal artery: branch of the internal iliac artery.
• Inferior rectal artery: branch of the internal pudendal artery.

Note

• The digestive process begins in the mouth and ends in the small intestine.
• The large intestine primarily absorbs remaining water from undigested food and allows bacterial fermentation of materials that cannot be digested further.
• The alimentary canal (gastrointestinal tract) is a continuous tube running from the mouth to the anus, where food is gradually digested as it passes through different compartments.