[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Digestive system](https://durgical.com/en/histology/#a-digestive) › Large intestine, appendix and anal canal [Histology](https://durgical.com/en/histology/) · [Digestive system](https://durgical.com/en/histology/#a-digestive) # Large intestine, appendix and anal canal - Organ The large intestine has no villi; its lining is straight glands full of mucus cells that absorb water and make stool slide. Updated 2026-11-01 **See it in 3D:** [Cecum](https://durgical.com/en/anatomy/cecum/) · [Appendix](https://durgical.com/en/anatomy/vermiform-appendix/) · [Ascending colon](https://durgical.com/en/anatomy/ascending-colon/) · [Transverse colon](https://durgical.com/en/anatomy/transverse-colon/) · [Sigmoid colon](https://durgical.com/en/anatomy/sigmoid-colon/) · [Rectum](https://durgical.com/en/anatomy/rectum/) · [Anal canal](https://durgical.com/en/anatomy/anal-canal/) ## Key points - Colon: no villi, straight crypts, abundant goblet cells, teniae coli. - Appendix: lymphoid follicles throughout the mucosa and submucosa. - Pectinate line: columnar above, squamous below; different nerves, vessels and cancers. - Ulcerative colitis: continuous, mucosal, crypt abscesses; Crohn: transmural, skip lesions, granulomas. - Appendicitis is confirmed by neutrophils in the muscularis propria. ## What it is The colon and rectum have a flat surface with straight, tightly packed crypts rich in goblet cells, designed to absorb water and lubricate stool. The outer longitudinal muscle gathers into three teniae coli. The appendix is a narrow tube packed with lymphoid follicles. The anal canal changes from columnar to squamous epithelium at the pectinate line, a landmark for hemorrhoids and anal cancers. ## Structure - Colon mucosa: no villi, straight tubular crypts, many goblet cells, absorptive colonocytes. - Muscularis externa: inner circular layer and three teniae coli; haustra are the pouches between them. - Appendix: crypts that are irregular, lymphoid follicles with germinal centres that may form a ring in the mucosa and submucosa, and a complete longitudinal layer. - Rectum: deeper crypts, many goblet cells, a continuous longitudinal muscle layer (the teniae spread out). - Anal canal: simple columnar epithelium above, a transitional zone, non-keratinized stratified squamous below the pectinate line, then keratinized skin with hairs at the anal verge. ## Above vs below the pectinate line | Feature | Above the pectinate line | Below the pectinate line | | --- | --- | --- | | Epithelium | Columnar (rectal type) | Stratified squamous | | Origin | Endoderm (hindgut) | Ectoderm (proctodeum) | | Pain sensation | Visceral, largely painless | Somatic, painful | | [Hemorrhoids](https://durgical.com/en/conditions/haemorrhoids/) | Internal, usually painless bleeding | External, painful when thrombosed | | Typical cancer | Adenocarcinoma | Squamous cell carcinoma (often HPV related) | ## Clinical notes - Ulcerative colitis: continuous inflammation from the rectum upward, limited to mucosa and submucosa, with crypt abscesses and distorted crypts. - Colorectal cancer usually develops from adenomatous polyps through dysplasia (the adenoma-carcinoma sequence). - Acute appendicitis: obstruction of the lumen, then neutrophils infiltrating the muscularis propria, the key histological criterion. - Diverticula are herniations of mucosa and submucosa through weak points where vessels cross the muscle wall. - Entamoeba histolytica causes flask-shaped ulcers of the colon, still seen in the region. ## Memory aid Above the line it is gut and silent, below it is skin and it hurts. ## Test yourself Think of the answer, then tap the question to see it. ## What features distinguish colonic mucosa from small-intestinal mucosa? The colon has no villi and no circular folds; it shows straight crypts packed with goblet cells. ## What histological finding confirms acute appendicitis? Neutrophils infiltrating the muscularis propria of the appendiceal wall. ## Which epithelium lines the anal canal below the pectinate line? Non-keratinized stratified squamous epithelium, which becomes keratinized skin at the anal verge. ## Which layers of the wall does ulcerative colitis usually affect? The mucosa and submucosa; transmural inflammation suggests Crohn disease instead. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/large-intestine-appendix-and-anal-canal/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Cecum](https://durgical.com/en/anatomy/cecum/) - [Appendix](https://durgical.com/en/anatomy/vermiform-appendix/) - [Ascending colon](https://durgical.com/en/anatomy/ascending-colon/) - [Transverse colon](https://durgical.com/en/anatomy/transverse-colon/) - [Sigmoid colon](https://durgical.com/en/anatomy/sigmoid-colon/) - [Rectum](https://durgical.com/en/anatomy/rectum/) - [Anal canal](https://durgical.com/en/anatomy/anal-canal/) ## Related - [Small intestine: villi, crypts, enterocytes, Paneth cells; duodenum vs jejunum vs ileum](https://durgical.com/en/histology/small-intestine-villi-crypts-enterocytes-paneth-cells-duodenum-vs-jejunum-vs-ile/) - [The GI tract wall: mucosa, submucosa, muscularis, serosa; enteric plexuses](https://durgical.com/en/histology/the-gi-tract-wall-mucosa-submucosa-muscularis-serosa-enteric-plexuses/) - [Enteroendocrine cells and GALT](https://durgical.com/en/histology/enteroendocrine-cells-and-galt/) ## Related conditions - [Ulcerative colitis](https://durgical.com/en/conditions/ulcerative-colitis/) - [Colorectal cancer](https://durgical.com/en/conditions/colorectal-cancer/) - [Acute appendicitis](https://durgical.com/en/conditions/acute-appendicitis/) - [Diverticular disease and diverticulitis](https://durgical.com/en/conditions/diverticular-disease-and-diverticulitis/) - [Haemorrhoids](https://durgical.com/en/conditions/haemorrhoids/) - [Crohn disease](https://durgical.com/en/conditions/crohn-disease/) ## Microorganisms - [Entamoeba histolytica](https://durgical.com/en/microbiology/entamoeba-histolytica/) - [Clostridioides difficile](https://durgical.com/en/microbiology/clostridioides-difficile/) - [Shigella](https://durgical.com/en/microbiology/shigella/) [← All of histology](https://durgical.com/en/histology/) Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice. Sources: [23.5 The Small and Large Intestines - Anatomy and Physiology 2e | OpenStax](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-5-the-small-and-large-intestines) (OpenStax (Rice University), 2022); [Small & Large Intestine | SEER Training](https://training.seer.cancer.gov/anatomy/digestive/regions/intestine.html) (National Cancer Institute (SEER Training), 2026); [23.1 Overview of the Digestive System - Anatomy and Physiology 2e | OpenStax](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-1-overview-of-the-digestive-system) (OpenStax (Rice University), 2022). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/histology/large-intestine-appendix-and-anal-canal/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/large-intestine-appendix-and-anal-canal/