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Some food material is passed from the small intestine to the large intestine. In the large intestine, bacteria break down any proteins and starches in chyme that were not digested fully in the small intestine. When all of the nutrients have been absorbed from chyme, the remaining waste material changes into semisolids that are called feces.
Here, the food is further broken down by mixing with gastric acid until it passes into the duodenum, the first part of the small intestine. The third stage, the intestinal phase, begins in the duodenum. Here, the partially digested food is mixed with a number of enzymes produced by the pancreas.
Digested food is now able to pass into the blood vessels in the wall of the intestine through either diffusion or active transport. The small intestine is the site where most of the nutrients from ingested food are absorbed. The inner wall, or mucosa, of the small intestine, is lined with intestinal epithelium, a simple columnar epithelium.
They blend into the surrounding tissue and are fixed in position (for example, the retroperitoneal section of the duodenum usually passes through the transpyloric plane). The retroperitoneal regions include the oral cavity , esophagus , pylorus of the stomach, distal duodenum , ascending colon , descending colon and anal canal .
It is separated from the ileum by the ileocecal valve (ICV), also called Bauhin's valve. It is also separated from the colon by the cecocolic junction. While the cecum is usually intraperitoneal, the ascending colon is retroperitoneal. [2] In herbivores, the cecum stores food material where bacteria are able to break down the cellulose.
The ileum follows the duodenum and jejunum and is separated from the cecum by the ileocecal valve (ICV). In humans, the ileum is about 2–4 m long, and the pH is usually between 7 and 8 (neutral or slightly basic). Ileum is derived from the Greek word εἰλεός (eileós), referring to a medical condition known as ileus. [citation needed]
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus.The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines.
In most vertebrates, digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing. Digestion is separated into four steps: Ingestion: placing food into the mouth (entry of food in the digestive system),