How is digestion different in the small and the large intestine

Special cells help absorbed nutrients cross the intestinal lining into your bloodstream. Your blood carries simple sugars, amino acids, glycerol, and some vitamins and salts to the liver. Your liver stores, processes, and delivers nutrients to the rest of your body when needed. The lymph system , a network of vessels that carry white blood cells and a fluid called lymph throughout your body to fight infection, absorbs fatty acids and vitamins. Your body uses sugars, amino acids, fatty acids, and glycerol to build substances you need for energy, growth, and cell repair.

Your hormones and nerves work together to help control the digestive process. Signals flow within your GI tract and back and forth from your GI tract to your brain. Cells lining your stomach and small intestine make and release hormones that control how your digestive system works.

These hormones tell your body when to make digestive juices and send signals to your brain that you are hungry or full. Your pancreas also makes hormones that are important to digestion. You have nerves that connect your central nervous system—your brain and spinal cord—to your digestive system and control some digestive functions.

For example, when you see or smell food, your brain sends a signal that causes your salivary glands to "make your mouth water" to prepare you to eat. When food stretches the walls of your GI tract, the nerves of your ENS release many different substances that speed up or delay the movement of food and the production of digestive juices.

The nerves send signals to control the actions of your gut muscles to contract and relax to push food through your intestines. Griffin P. Rodgers explaining the importance of participating in clinical trials. Clinical trials that are currently open and are recruiting can be viewed at www. The NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public.

Why is digestion important? How does my digestive system work? How does food move through my GI tract? How does my digestive system break food into small parts my body can use? What happens to the digested food? How does my body control the digestive process? Clinical Trials What is the digestive system? Summary Read the full fact sheet. On this page. The mouth and oesophagus The stomach The small intestine Pancreas Liver The large intestine Common problems in the digestive system Where to get help Things to remember.

The mouth and oesophagus Digestion begins in the mouth. The stomach The food passes through a sphincter, or small muscle ring, into the stomach. The small intestine Once in the duodenum, the food is mixed with more digestive enzymes from the pancreas and bile from the liver.

Pancreas The pancreas is one of the largest glands in the human body. Liver The liver has a number of different roles in the body, including: breaking down fats, using bile stored in the gall bladder processing proteins and carbohydrates filtering and processing impurities, drugs and toxins generation of glucose for short-term energy needs from other compounds like lactate and amino acids. The large intestine Once all the nutrients have been absorbed, the waste is moved into the large intestine, or bowel.

Common problems in the digestive system Some common problems include: colitis — inflammation of the bowel diverticulitis — inflammation of pouches lining the small intestine gastroenteritis — an infection that causes vomiting and diarrhoea heartburn — when the contents of the stomach back up into the oesophagus ulcer — a hole in the mucous membrane lining the stomach or duodenum.

Where to get help Your doctor Things to remember Food is broken down by the digestive system to give energy to every cell in the body. The digestive tract starts at the mouth and ends at the anus. Give feedback about this page. Was this page helpful? Yes No. The waste parts of food that the body can't use are what leave the body as feces. How Does Digestion Work? The small intestine is made up of three parts: the duodenum due-uh-DEE-num , the C-shaped first part the jejunum jih-JU-num , the coiled midsection the ileum IH-lee-um , the final section that leads into the large intestine The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi VIH-lie.

The large intestine has three parts: The cecum SEE-kum is the beginning of the large intestine. The appendix , a small, hollow, finger-like pouch, hangs at the end of the cecum. Doctors believe the appendix is left over from a previous time in human evolution. It no longer appears to be useful to the digestive process. The colon extends from the cecum up the right side of the abdomen, across the upper abdomen, and then down the left side of the abdomen, finally connecting to the rectum.

The colon has three parts: the ascending colon and the transverse colon, which absorb fluids and salts; and the descending colon, which holds the resulting waste. Bacteria in the colon help to digest the remaining food products. The rectum is where feces are stored until they leave the digestive system through the anus as a bowel movement.

It takes hours for our bodies to fully digest food. Print Send to a Friend. All rights reserved. Screening for fecal occult blood tests and colonoscopy is recommended for those over 50 years of age.

Food residue leaving the sigmoid colon enters the rectum in the pelvis, near the third sacral vertebra. The final These valves help separate the feces from gas to prevent the simultaneous passage of feces and gas. Finally, food residue reaches the last part of the large intestine, the anal canal , which is located in the perineum, completely outside of the abdominopelvic cavity.

This 3. The anal canal includes two sphincters. The internal anal sphincter is made of smooth muscle, and its contractions are involuntary. The external anal sphincter is made of skeletal muscle, which is under voluntary control. Except when defecating, both usually remain closed. There are several notable differences between the walls of the large and small intestines. For example, few enzyme-secreting cells are found in the wall of the large intestine, and there are no circular folds or villi.

Other than in the anal canal, the mucosa of the colon is simple columnar epithelium made mostly of enterocytes absorptive cells and goblet cells. In addition, the wall of the large intestine has far more intestinal glands, which contain a vast population of enterocytes and goblet cells.

These goblet cells secrete mucus that eases the movement of feces and protects the intestine from the effects of the acids and gases produced by enteric bacteria. The enterocytes absorb water and salts as well as vitamins produced by your intestinal bacteria. Figure 5. LM x Three features are unique to the large intestine: teniae coli, haustra, and epiploic appendages Figure 6.

The teniae coli are three bands of smooth muscle that make up the longitudinal muscle layer of the muscularis of the large intestine, except at its terminal end. Attached to the teniae coli are small, fat-filled sacs of visceral peritoneum called epiploic appendages.

The purpose of these is unknown. Although the rectum and anal canal have neither teniae coli nor haustra, they do have well-developed layers of muscularis that create the strong contractions needed for defecation. The stratified squamous epithelial mucosa of the anal canal connects to the skin on the outside of the anus.

This mucosa varies considerably from that of the rest of the colon to accommodate the high level of abrasion as feces pass through. Two superficial venous plexuses are found in the anal canal: one within the anal columns and one at the anus. Depressions between the anal columns, each called an anal sinus , secrete mucus that facilitates defecation.

The pectinate line or dentate line is a horizontal, jagged band that runs circumferentially just below the level of the anal sinuses, and represents the junction between the hindgut and external skin. The mucosa above this line is fairly insensitive, whereas the area below is very sensitive. The resulting difference in pain threshold is due to the fact that the upper region is innervated by visceral sensory fibers, and the lower region is innervated by somatic sensory fibers.

Most bacteria that enter the alimentary canal are killed by lysozyme, defensins, HCl, or protein-digesting enzymes. However, trillions of bacteria live within the large intestine and are referred to as the bacterial flora. Most of the more than species of these bacteria are nonpathogenic commensal organisms that cause no harm as long as they stay in the gut lumen.

In fact, many facilitate chemical digestion and absorption, and some synthesize certain vitamins, mainly biotin, pantothenic acid, and vitamin K. Some are linked to increased immune response. A refined system prevents these bacteria from crossing the mucosal barrier. Dendritic cells open the tight junctions between epithelial cells and extend probes into the lumen to evaluate the microbial antigens. The dendritic cells with antigens then travel to neighboring lymphoid follicles in the mucosa where T cells inspect for antigens.

This process triggers an IgA-mediated response, if warranted, in the lumen that blocks the commensal organisms from infiltrating the mucosa and setting off a far greater, widespread systematic reaction. The residue of chyme that enters the large intestine contains few nutrients except water, which is reabsorbed as the residue lingers in the large intestine, typically for 12 to 24 hours. Thus, it may not surprise you that the large intestine can be completely removed without significantly affecting digestive functioning.

For example, in severe cases of inflammatory bowel disease, the large intestine can be removed by a procedure known as a colectomy. Often, a new fecal pouch can be crafted from the small intestine and sutured to the anus, but if not, an ileostomy can be created by bringing the distal ileum through the abdominal wall, allowing the watery chyme to be collected in a bag-like adhesive appliance. In the large intestine, mechanical digestion begins when chyme moves from the ileum into the cecum, an activity regulated by the ileocecal sphincter.

Right after you eat, peristalsis in the ileum forces chyme into the cecum. When the cecum is distended with chyme, contractions of the ileocecal sphincter strengthen. Once chyme enters the cecum, colon movements begin. Mechanical digestion in the large intestine includes a combination of three types of movements. The presence of food residues in the colon stimulates a slow-moving haustral contraction.

This type of movement involves sluggish segmentation, primarily in the transverse and descending colons. When a haustrum is distended with chyme, its muscle contracts, pushing the residue into the next haustrum. These contractions occur about every 30 minutes, and each last about 1 minute. These movements also mix the food residue, which helps the large intestine absorb water.

The second type of movement is peristalsis, which, in the large intestine, is slower than in the more proximal portions of the alimentary canal. The third type is a mass movement. These strong waves start midway through the transverse colon and quickly force the contents toward the rectum. Mass movements usually occur three or four times per day, either while you eat or immediately afterward. Distension in the stomach and the breakdown products of digestion in the small intestine provoke the gastrocolic reflex , which increases motility, including mass movements, in the colon.

Fiber in the diet both softens the stool and increases the power of colonic contractions, optimizing the activities of the colon. Although the glands of the large intestine secrete mucus, they do not secrete digestive enzymes. Therefore, chemical digestion in the large intestine occurs exclusively because of bacteria in the lumen of the colon. Through the process of saccharolytic fermentation , bacteria break down some of the remaining carbohydrates. This results in the discharge of hydrogen, carbon dioxide, and methane gases that create flatus gas in the colon; flatulence is excessive flatus.