How does the intestine work? - Informed Health Online - NCBI Bookshelf
The small intestine is a tubular structure within the abdominal cavity that carries the food in continuation with the stomach up to the colon from where the large. The small intestine or small bowel is the part of the gastrointestinal tract between the stomach The length of the small intestine can vary greatly, from as short as m ( ft) to as long as m ( ft). The typical length in The ileum joins to the cecum of the large intestine at the ileocecal junction. The jejunum and . In the right lower abdomen, the small intestine leads into the large intestine, which is roughly 1 to meters long. The large.
The digestive system The small intestine In the small intestine, enzymes substances produced by the body break down nutrients such as carbohydrates, proteins or fats into their building blocks. These enzymes are produced in the salivary glands in the mouth, in the pancreas and in the intestinal cells. The intestinal cells absorb the building blocks for example sugar, amino acids or fatty acids together with vitamins, salts and water.
From there, most of the nutrients enter the bloodstream to be carried to the rest of the body. The small intestinal cells also produce various intestinal hormones. These hormones influence things like the production of bile or pancreatic juice.
They also cause more water to be released into the intestine and make you feel full. The large intestine In the right lower abdomen, the small intestine leads into the large intestine, which is roughly 1 to 1. The large intestine is made up of the cecum, the appendix, the colon and the rectum, which ends at the anus in the anal canal. In the large intestine, strong, wave-like movements help to push the contents of the intestine towards the anus. The urge to go to the toilet and empty your bowels is triggered when stool enters the rectum.
If we suppress this urge, the rectum temporarily stores the stool.
How often bowel movements occur varies greatly from person to person: It is completely normal to empty your bowel anywhere between three times a day to three times a week. The frequency mostly depends on how much fiber you get in your diet. Another important task performed by the large intestine is the absorption of water and salts. There are also millions of bacteria in the large intestine.
These bacteria break down proteins in the food to produce protein building blocks amino acids. And they make the vital vitamins B and K. The stomach is made up of five layers. The next layer, the submucosa, is covered by muscularis which moves and helps in the mixing of the food. Then comes the two layers of covering called subserosa and serosa the outermost layer. The folded lining of the stomach allows it to expand when filled with food. Enzymes and stomach juices begin the digestion of fats and proteins by separating them into their basic parts of amino acids and fatty acids.
Only a small amount of carbohydrate digestion happens in the stomach because the stomach acids are so strong. However, substances like water and alcohol are absorbed directly from the stomach.
The stomach takes up to five hours to mix and digest solid food. Once in the small intestine, carbohydrate digestion starts again and your body starts to absorb the nutrients from the food. A thick, ring-like smooth muscle, the pyloric sphincter, separates the stomach from the duodenum of the small intestine.
This muscle is usually closed, but relaxes and opens to let the acid chyme into the small intestine, then closes to keep the chyme from going back into the stomach. Small Intestine Small Intestine Inside Large Intestine The small intestine is divided into three parts—the duodenum, jejunum and ileum.
The small intestine is about 20 feet long and 1 inch wide.Structure Of The Small Intestine - Functions Of The Small Intestine - What Are Villi
By putting your flattened palm on your belly button, you are covering most of the small space where the small intestine is coiled up. The small intestine is lined with protective mucus to prevent it from digesting itself.
The lining has thousands of tiny folds and projections called villi. There are tinier projects on each villus called microvilli.
Human Intestines | Interactive Anatomy Guide
These folds make a huge area for absorbing food. Amino acids, sugars, vitamin C, the B vitamins, iron, calcium and magnesium are carried through the blood stream to your liver where they are processed and sent to the rest of the body. Fatty acid, cholesterol, and vitamins A, D, E, and K go into the lymph system and then into the blood.
These also go to the liver, get processed and sent out to other cells in the body. Duodenum It is a inch long C-shaped tube found around the head of the pancreas which forms the first part of the small intestine right after the stomach. The food, now chyme, enters from the stomach into the duodenum where it is mixed together with the bile and other digestive juices produced by the accessory digestive organs and drained into the duodenum.
Absorption of food also begins here with the absorption of vitamins, minerals and other nutrients. In particular, before the food passes into the next part of the small intestine iron, calcium and magnesium are absorbed here. The rest of the food is passed into the jejunum. Jejunum Function The second middle section of the small intestine is a coiled tube which is thicker and more vascular than the ileum. It lies in the belly button area of the abdomen. There are small fingerlike projections in the wall of the jejunum called villi.
These villi are covered with smaller projections called microvilli. The villi increase the surface area of the jejunum and allows much more absorption of nutrients in this part of the small intestine—most of the food absorption is done in this part of the digestive tract. Simple sugars, water soluble vitamins except vitamin C and some Bs and amino acids made from the food is passed from the villi into the blood stream while the fat is passed into the lymph capillaries. The rest of the food passes into the ileum.
Ileum The last part of the small intestine is mainly the pelvic region.
The Small Intestine
It looks very similar to the jejunum. However, the nature of the small intestine gradually changes. It is thinner and has fewer blood vessels as compared to the jejunum. The last absorption of nutrients from the food takes place here—amino acids the end products of protein digestionfat-soluble vitamins A, D, E, and Kfatty acids the end products of fat digestioncholesterol, sodium, potassium alcohol, and B The terminal ileum is an important part as this is where vitamin B12 is absorbed into the blood capillaries.
The unabsorbed and undigested food then passes from the ileum into the cecum, the beginning of the large intestine. This food residue is full of bacteria. Large Intestine Large Intestine — Click for larger image The large intestine forms the last part of the digestive tract, which is about 5 feet long and wider than the small intestine.
The surface area on the inside of the large intestine is smaller than the small intestine. The large intestine can be divided into the cecum, colon and rectum. The undigestible food waste passes from the small intestine into the cecum which then passes into the colon further divided into ascending colon, transverse colon, descending colon and sigmoid colon where the fluids and salts are absorbed.
Anatomy and Function of the Digestive System
The undigested food moves up the ascending colon, across the transverse colon, down the descending colon and into the rectum. The colon soaks up to 50 fluid ounces of water every day. After absorption, the remaining undigested matter is squeezed into a bundle called feces.
Feces is made of fiber, undigested food, cells that slough off the lining of the intestines and bacteria. They make vitamin K and B12 which is absorbed by the colon wall, break down amino acids and make nitrogen, live off of fiber which makes gas. When the bacteria finish with the feces, it is passed into the rectum, where it is stored until it is passed out through the anus as a bowel movement.
The anus has voluntary and involuntary sphincter muscles which can tell the difference between gas and solid contents. A vestigial organ an organ that had a purpose in the past but is now useless or close to itthe appendix, is attached to the large intestine at the cecum. Though this organ is potentially of no use, it can cause pains and complications once it gets inflamed, a disorder called appendicitis. Accessory Digestive Organs and Glands Though not directly part of the digestive tract, the accessory digestive organs play a major role in digestion.
The accessory digestive organs include the salivary glands, pancreas, liver and gallbladder. Glands are organs that secrete hormones. Salivary Glands There are three pairs of salivary glands: It also helps break down starches in the food. Pancreas A carrot-shaped gland located behind and under the stomach, the pancreas acts both as an endocrine gland and an exocrine gland.
From the exocrine part it secretes pancreatic enzymes amylase and lipase which pass through the pancreatic duct into the small intestine the duodenum.
The pancreatic duct joins the bile duct. These enzymes aid in the further breakdown of food, mainly the carbohydrate, protein and lipid part of the food. From the endocrine part it secretes insulin and glucagon. Insulin enables you to digest and metabolize carbohydrates. The pancreas also secretes an antacid to help settle an upset stomach. It is the largest organ of the human body and is below the diaphragm in the upper epigastric region of the abdomen. It has many functions including production of chemicals necessary for digestion, synthesis of protein and detoxification.
The major function of the liver is to produce bile yellowish-green fluid which aids in the digestion and absorption of fats. It also stores glucose, iron and vitamins A, B12, D etc.
The liver also sends out the nutrients and substances digested from the food to the cells of the body. Gallbladder The gallbladder is a small organ located just below the liver. It is about 3 inches long and shaped like a hollow balloon. Its main function is to store bile produced by the liver and release it into the duodenum when food that contains fat needs to be broken down and absorbed. The bile in the gallbladder becomes more concentrated and more effective in breaking down the fat.
Gallstones are a common disorder of the gallbladder.