• The distal orifice of the digestive tract located between the rectum and the external surface of the body, comprising glandular, transitional, and squamous epithelium.
  CDISC Terminology
  Clinical Data Interchange Standards Consortium (CDISC), 2021
• The external opening at the end of digestive tract where feces are expelled.
  Harvard Dictionary of Health Terms
  Harvard Medical Publishing, 2011
• The external outlet of the GASTROINTESTINAL TRACT.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2025
• The lower opening of the digestive tract, lying in the cleft between the buttocks, through which fecal matter is extruded.
  NCI
  U.S. National Cancer Institute, 2021
• The opening of the rectum to the outside of the body.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• The anus is the opening at the end of the digestive tract where stool leaves the body. The rectum is the section of the digestive tract above the anus where stool is held before it passes out of the body through the anus.
  Merck Manuals
  Merck & Co., Inc., 2025
• Anus, terminal opening of the anal canal, the portion of the digestive tract through which fecal material is excreted.
  Encyclopedia Britannica
  Encyclopedia Britannica, Inc., 2025