The duodenum also uses bile from your gallbladder, liver, and pancreas to help digest food. Jejunum: The middle section of the small intestine carries food through rapidly, with wave-like muscle contractions, towards the ileum. Ileum: This last section is the longest part of your small intestine. The ileum is where most of the nutrients from your food are absorbed before emptying into the large intestine.
How can the small intestine digest so much? The small intestine has three features which allow it to have such a huge absorptive surface area packed into a relatively small space: Mucosal folds: The inner surface of the small intestine is not flat, but thrown into circular folds. This not only increases the surface area, but helps regulate the flow of digested food through your intestine.
Villi: The folds form numerous tiny projections which stick out into the open space inside your small intestine or lumen , and are covered with cells that help absorb nutrients from the food that passes through. Microvilli: The cells on the villi are packed full of tiny hairlike structures called microvilli. This helps increase the surface of each individual cell, meaning that each cell can absorb more nutrients.
What Is the Large Intestine? The large intestine is made up of the following parts: Cecum: This first section of your large intestine looks like a pouch, about two inches long.
It takes in digested liquid from the ileum and passes it on to the colon. Colon: This is the major section of the large intestine; you may have heard people talk about the colon on its own. The colon is also the principal place for water reabsorption, and absorbs salts when needed.
The colon consists of four parts: Ascending colon: Using muscle contractions, this part of the colon pushes any undigested debris up from the cecum to a location just under the right lower end of the liver. Transverse colon: Food moves through this second portion of the colon, across your front or anterior abdominal wall, traveling from left to right just under your stomach.
Descending colon: The third portion of colon pushes its contents from just near the spleen , down to the lower left side of your abdomen. The duodenum accomplishes a good deal of chemical digestion, as well as a small amount of nutrient absorption see part 3 ; the main function of the jejunum and ileum is to finish chemical digestion enzymatic cleavage of nutrients and absorb these nutrients along with water and vitamins.
The brush border of the small intestine contains enzymes that complete the process of chemical digestion. Table 1 lists these enzymes and their roles. The rings of smooth muscle in the wall of the small intestine repeatedly contract and relax in a process called segmentation.
This moves intestinal contents back and forth. Segmentation distends the small intestine but does not drive chyme through the tract; instead, it mixes it with digestive juices and then pushes it against the mucosa to allow nutrient absorption. The transport of nutrients across the membranes of the intestinal epithelial cells into the villi, and subsequently into blood capillaries and lacteals, occurs either passively or actively.
Passive transport requires no energy and involves the diffusion of simple molecules along a concentration gradient — movement from an area where they are in high concentration to one where they are in lower concentration — in this case, the blood. Water and some vitamins can cross the gut wall passively. Active transport requires energy to pull molecules out of the intestinal lumen against a concentration gradient.
Digested carbohydrates enter the blood capillaries irrigating each villus. Glucose is actively absorbed via a co-transport mechanism using sodium ions as carriers. Other absorbable monosaccharides include galactose from milk and fructose from fruit.
Most products of protein digestion amino acids are also absorbed through an active co-transport mechanism with sodium ions and enter the blood capillary system of each villus. They then travel to the liver via the hepatic portal vein. Digested fats mingle with bile salts, which ferry them to the mucosa where they are coated with lipoproteins and aggregated into small molecules called chylomicrons, which are taken into the central lacteals of the villi.
They travel with lymph to the thoracic duct, where they enter the blood supply. If there is malabsorption of fats, these pass into the large intestine, where they form pale, oily, foul-smelling stools steatorrhoea — see part 3.
When that happens, certain fat-soluble vitamins A, D, E and K may also not be absorbed, potentially leading to deficiencies. The vitamin B complex encompasses eight water-soluble vitamins that are essential for key functions of the body, including red blood cell formation, maintenance of healthy hair and nails, and healthy functioning of the brain and heart.
Vitamin B1. Essential for metabolism, vitamin B1 also plays a role in healthy nerve conduction and muscle contraction.
It is found in fortified foods such as bread and cereals, but also in eggs, fish, nuts, legumes and certain meats Wiley and Gupta, Vitamin B1 deficiency is common in people who have a poor diet for example, homeless people and can cause a range of disorders including beriberi. Vitamin B This vitamin is essential for red blood cell development, normal functioning of the nervous system, cell metabolism and DNA synthesis. The richest natural sources of vitamin B12 are liver and kidney, but it is also present in meat, fish, dairy products, eggs and shellfish.
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