The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before being removed by defecation. The colon is the longest portion of the large intestine, and the terms are often used interchangeably but most sources define the large intestine as the combination of the cecum, colon, rectum, and anal canal. Some other sources exclude the anal canal.
Colonic crypts (intestinal glands) within four tissue sections. The cells have been stained to show a brown-orange color if the cells produce the mitochondrial protein cytochrome c oxidase subunit I (CCOI), and the nuclei of the cells (located at the outer edges of the cells lining the walls of the crypts) are stained blue-gray with haematoxylin. Panels A, B were cut across the long axes of the crypts and panels C, D were cut parallel to the long axes of the crypts. In panel A the bar shows 100 µm and allows an estimate of the frequency of crypts in the colonic epithelium. Panel B includes three crypts in cross-section, each with one segment deficient for CCOI expression and at least one crypt, on the right side, undergoing fission into two crypts. Panel C shows, on the left side, a crypt fissioning into two crypts. Panel D shows typical small clusters of two and three CCOI deficient crypts (the bar shows 50 µm). The images were made from original photomicrographs, but panels A, B and D were also included in an article
Micrograph of normal large instestinal crypts.
Anatomy of normal large intestinal crypts
Histological section.
Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions. In chemical digestion, enzymes break down food into the small compounds that the body can use.
Venus Flytrap (Dionaea muscipula) leaf
Trophozoites of Entamoeba histolytica with ingested erythrocytes
A Catalina Macaw's seed-shearing beak
Squid beak with ruler for size comparison
