{"id":244,"date":"2024-03-23T09:24:03","date_gmt":"2024-03-23T09:24:03","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/?post_type=chapter&#038;p=244"},"modified":"2024-11-30T15:02:04","modified_gmt":"2024-11-30T15:02:04","slug":"3-1-digestion-and-absorption","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/chapter\/3-1-digestion-and-absorption\/","title":{"raw":"3.3 Digestion and absorption","rendered":"3.3 Digestion and absorption"},"content":{"raw":"<h1>Digestion<\/h1>\r\n<span>Digestion is the mechanical and chemical break down of food into small organic fragments. During the process of digestion large complex\u00a0\u00a0<\/span><span>proteins, polysaccharides, and lipids molecules are reduced to simple molecules\u00a0 such as simple sugar, acids acids and fatty acids\u00a0 before they can be absorbed by the intestinal epithelial cells.\u00a0<\/span>\r\n<h3>Main Organs of the Digestive System<\/h3>\r\n<img src=\"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/a\/a7\/Digestive-system-for-kids.png\/398px-Digestive-system-for-kids.png?20140510192231\" alt=\"File:Digestive-system-for-kids.png\" class=\"aligncenter\" \/>\r\n<p style=\"text-align: center\"><a href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Digestive-system-for-kids.png\" target=\"_blank\" rel=\"noopener\">\"Digestive-system\"<\/a><span>\u00a0by\u00a0<\/span><a>Leysi24 via Wikimedia commons<\/a><a><\/a><a><\/a><span>\u00a0is licensed under\u00a0<\/span><a href=\"http:\/\/creativecommons.org\/licenses\/by\/3.0\" target=\"_blank\" rel=\"noopener\">CC BY 3.0<\/a><\/p>\r\n\r\n<ol>\r\n \t<li><strong>Mouth<\/strong>: Digestion of food\u00a0 begins in the mouth. The food is chewed and mixed with saliva in the mouth so as to break it down into a form that can be easily swallowed and digested.<\/li>\r\n \t<li><strong>Esophagus<\/strong>: It is the muscular tube that connects the mouth to the stomach. The food\u00a0 moves from the mouth through\u00a0 esophagus by a wave-like muscle contraction process called\u00a0[pb_glossary id=\"910\"] peristalsis[\/pb_glossary]\u00a0 .<\/li>\r\n \t<li><strong>Stomach<\/strong>: The food is further broken down in the stomach\u00a0 using stomach acids and enzymes.\u00a0 The food is now turned into a semi-liquid form called[pb_glossary id=\"912\"] chyme[\/pb_glossary].T<span>he stomach links the esophagus to the duodenum. The empty stomach is only about the size of\u00a0 fist, but can stretch to hold as much as 4 liters of food and fluid,\u00a0 and then return to its resting size when empty. There are four main regions in the\u00a0stomach: the <strong>cardia, fundus, body, and pylorus.<\/strong><\/span>\r\n<ul>\r\n \t<li><span>The\u00a0<\/span><span data-type=\"term\">cardia<\/span><span>\u00a0(or cardiac region) : This is the point where the esophagus connects to the stomach and through which food passes into the stomach. <\/span><\/li>\r\n \t<li><span>Fundus : is located inferior to the diaphragm, above and to the left of the cardia. It\u00a0 is the dome-shaped <\/span><span>. <\/span><\/li>\r\n \t<li><span>Body : This is <\/span><span>\u00a0the main part of the stomach and is located below the fundus. <\/span><\/li>\r\n \t<li><span>Pylorus : This is\u00a0 funnel-shaped. The\u00a0 <\/span><span data-type=\"term\">pylorus<\/span><span> connects the stomach to the duodenum. The wider end of the funnel is called\u00a0 the <\/span><strong>pyloric antrum<\/strong><span><strong>,<\/strong> This\u00a0 connects to the body of the stomach. The narrower end is called the <\/span><strong>pyloric canal<\/strong><span><strong>,<\/strong> which connects to the duodenum. The <\/span><span data-type=\"term\">pyloric sphincter<\/span><span> is located at the bottom of the stomach, between the stomach and the duodenum. It controls stomach emptying. In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a <\/span><span data-type=\"term\">ruga<\/span><span>.<\/span><\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Small Intestine<\/strong>: The small intestine includes the the duodenum, jejunum, and ileum. Most of the digestion and absorption of nutrients occurs in the small intestine. It is t<span>he longest part of the alimentary canal, the small intestine is about 3.05 meters (10 feet) long in a living person. The diameter of the small intestine is about 2.54 cm (1 in).The folds and projections of the lining of the small intestine gives\u00a0 an enormous surface area of about\u00a0 200 m<sup>2\u00a0<\/sup><\/span><\/li>\r\n \t<li><strong>Large Intestine<\/strong>: The large intestine <span> runs from the appendix to the anus and <\/span>includes the cecum, colon, and rectum. The water and salts from the material that has not been digested are absorbed in the large intestine. The large intestine\u00a0 is responsible for forming and expelling feces. The large intestine frames the small intestine on three sides and has a\u00a0 diameter more than twice of the small intestine, about 3 inches. <span>The ileocecal valve, located at the opening between the ileum and the large intestine. It controls the flow of chyme from the small intestine to the large intestine. The cecum is a sac-like structure that is suspended inferior to the ileocecal valve. It is about 6 cm (2.4 in) long. It\u00a0 receives the contents of the ileum, and continues the absorption of water and salts. Attached to the cecum is the appendix (or vermiform appendix) which is a winding tube . The 7.6-cm (3-in) long appendix contains lymphoid tissue, suggesting an immunologic function. The cecum blends seamlessly with the colon. On the right side of the abdomen, the food residue initially passes through the ascending colon. The colon becomes the transverse colon at the inferior surface of the liver, where it bends to form the right colic flexure (hepatic flexure).The final third of the transverse colon marks the start of the area known as the hindgut. After passing through the transverse colon, food waste reaches the left side of the abdomen, where it reaches the left colic flexure (splenic flexure), where the colon angles abruptly just inferior to the spleen. From there, food residue goes through the descending colon, which runs down the left side of the posterior abdominal wall. It becomes the s-shaped sigmoid colon after entering the pelvis .Food residue leaving the sigmoid colon enters the\u00a0rectum\u00a0in the pelvis, near the third sacral vertebra. The final 20.3 cm (8 in) of the alimentary canal, the rectum extends anterior to the sacrum and coccyx.\u00a0<\/span><\/li>\r\n \t<li><strong>Anus<\/strong>: This is the\u00a0 final part of the digestive tract. Anus expels feces\u00a0 from the body. T<span>he anal canal is located in the perineum and is\u00a0 completely outside of the abdominopelvic cavity. This 3.8\u20135 cm (1.5\u20132 in) long structure opens to the exterior of the body at the anus. The anal canal has two sphincters namely\u00a0 the internal anal sphincter\u00a0 and the external sphincter .The internal 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.\u00a0 Both the sphincters usually remain closed except when defecating.<\/span><\/li>\r\n<\/ol>\r\n<h3>Accessory Organs of the digestive system<\/h3>\r\n<ol>\r\n \t<li><strong>Liver<\/strong>: The bile is produced in the liver\u00a0 which helps digest fats.<\/li>\r\n \t<li><strong>Gallbladder<\/strong>: The bile produced in the liver is stored and concentrated in the Gall bladder from where it is released\u00a0 into the small intestine.<\/li>\r\n \t<li><strong>Pancreas<\/strong>: Produces digestive enzymes and bicarbonate, which are released into the small intestine to aid in digestion.<\/li>\r\n<\/ol>\r\n<h3>Phases of Digestion<\/h3>\r\n<ol>\r\n \t<li><strong>Cephalic Phase<\/strong>: Triggered by the sight, smell, or thought of food, stimulating saliva and digestive juices.<\/li>\r\n \t<li><strong>Gastric Phase<\/strong>: Begins when food enters the stomach, stimulating the release of gas<\/li>\r\n \t<li><strong>Intestinal Phase:<\/strong> Starts when chyme enters the small intestine, triggering the release of digestive enzyme and bile<\/li>\r\n<\/ol>\r\n<div class=\"scroller-positioner\">\r\n<div class=\"content\">\r\n<div class=\"main\" id=\"cib-chat-main\" role=\"feed\">\r\n<div class=\"message\">\r\n<div class=\"content user-select-text\" aria-label=\"Sent by Copilot: The digestion of carbohydrates, proteins, and fats involves specific enzymes and processes that break down these macronutrients into their absorbable forms. Here's a detailed look at each: ### Carbohydrate Digestion 1. **Mouth**: Digestion begins with salivary amylase in the saliva, which breaks down starches into maltose and dextrins. 2. **Stomach**: Carbohydrate digestion pauses in the acidic environment of the stomach. 3. **Small Intestine**: Pancreatic amylase continues the breakdown of starches into maltose. Enzymes like maltase, sucrase, and lactase on the intestinal brush border convert disaccharides into monosaccharides (glucose, fructose, and galactose). 4. **Absorption**: Monosaccharides are absorbed into the bloodstream through the intestinal lining[^1^][^2^]. ### Protein Digestion 1. **Stomach**: Proteins are denatured by stomach acid (HCl) and broken down into smaller peptides by the enzyme pepsin. 2. **Small Intestine**: Pancreatic enzymes (trypsin, chymotrypsin, and carboxypeptidase) further break down peptides into smaller peptides and amino acids. Brush border enzymes (peptidases) complete the digestion into amino acids. 3. **Absorption**: Amino acids are absorbed into the bloodstream through the intestinal lining[^1^][^2^]. ### Fat Digestion 1. **Mouth**: Minor digestion of fats begins with lingual lipase. 2. **Stomach**: Gastric lipase continues the digestion of fats into smaller droplets. 3. **Small Intestine**: Bile from the liver emulsifies fats, increasing the surface area for pancreatic lipase to act. Pancreatic lipase breaks down triglycerides into monoglycerides and free fatty acids. 4. **Absorption**: Monoglycerides and fatty acids form micelles, which are absorbed into the intestinal cells. Inside the cells, they are reassembled into triglycerides and packaged into chylomicrons, which enter the lymphatic system and then the bloodstream[^1^][^2^][^3^]. Would you like more information on any specific part of these processes or how they are regulated?\">\r\n<div class=\"ac-container ac-adaptiveCard\">\r\n<div class=\"ac-textBlock\">\r\n<h3>Carbohydrate Digestion<\/h3>\r\n<ol>\r\n \t<li><strong>Mouth<\/strong>: Digestion begins with salivary amylase in the saliva, which breaks down starches into maltose and dextrins.<\/li>\r\n \t<li><strong>Stomach<\/strong>: Carbohydrate digestion pauses in the acidic environment of the stomach.<\/li>\r\n \t<li><strong>Small Intestine<\/strong>: Pancreatic amylase continues the breakdown of starches into maltose. Enzymes like maltase, sucrase, and lactase on the intestinal brush border convert disaccharides into monosaccharides (glucose, fructose, and galactose).<\/li>\r\n \t<li><strong>Absorption:<\/strong> Monosaccharides are absorbed into the bloodstream through the intestinal lining<\/li>\r\n<\/ol>\r\n<h3>Protein Digestion<\/h3>\r\n<ol>\r\n \t<li><strong>Stomach<\/strong>: Proteins are denatured by stomach acid (HCl) and broken down into smaller peptides by the enzyme pepsin.<\/li>\r\n \t<li><strong>Small Intestine<\/strong>: Pancreatic enzymes (trypsin, chymotrypsin, and carboxypeptidase) further break down peptides into smaller peptides and amino acids. Brush border enzymes (peptidases) complete the digestion into amino acids.<\/li>\r\n \t<li><strong>Absorption:<\/strong> Aminoacids are absorbed into the bloodstream through the intestinal lining<\/li>\r\n<\/ol>\r\n<h3>Fat Digestion<\/h3>\r\n<ol>\r\n \t<li><strong>Mouth<\/strong>: Minor digestion of fats begins with lingual lipase.<\/li>\r\n \t<li><strong>Stomach<\/strong>: Gastric lipase continues the digestion of fats into smaller droplets.<\/li>\r\n \t<li><strong>Small Intestine<\/strong>: Bile from the liver emulsifies fats, increasing the surface area for pancreatic lipase to act. Pancreatic lipase breaks down triglycerides into monoglycerides and free fatty acids.<\/li>\r\n \t<li><strong>Absorption<\/strong>: Monoglycerides and fatty acids form micelles, which are absorbed into the intestinal cells, where they are reassembled in to triglycerides and are packaged into chylomicrons which then enter the lymphatic system and then the blood stream.<\/li>\r\n<\/ol>\r\n<div class=\"textbox shaded\"><a href=\"https:\/\/youtu.be\/2uL4b1yMhm8?si=_foOGHX_-xid-S2v\">Watch the video <span style=\"text-align: initial;font-size: 1em\">Human Digestive System| Middle School Science | Khan Academy<\/span><\/a><\/div>\r\n&nbsp;\r\n<div id=\"player\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"player-container-outer\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"player-container-inner\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"player-container\" role=\"complementary\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"container\" class=\"style-scope ytd-player\">\r\n<div class=\"html5-video-player ytp-transparent ytp-exp-bottom-control-flexbox ytp-modern-caption ytp-exp-ppp-update ytp-cairo-refresh ytp-livebadge-color-control ytp-cairo-refresh-signature-moments ytp-bigboards ytp-large-width-mode ytp-fine-scrubbing-exp ytp-fit-cover-video ytp-hide-info-bar ytp-heat-map-v2 ytp-heat-map ytp-ce-shown ytp-iv-drawer-enabled ytp-autonav-endscreen-cancelled-state playing-mode ytp-branding-shown ytp-autohide\" id=\"movie_player\" data-version=\"\/s\/player\/b46bb280\/player_ias.vflset\/en_US\/base.js\" aria-label=\"YouTube Video Player\">\r\n<div class=\"ytp-chrome-bottom\" data-layer=\"9\">\r\n<div class=\"ytp-chrome-controls\">\r\n<div class=\"ytp-left-controls\">\r\n<div class=\"textbox shaded\">\r\n<div id=\"player\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"player-container-outer\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"player-container-inner\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"player-container\" role=\"complementary\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"container\" class=\"style-scope ytd-player\">\r\n<div class=\"html5-video-player ytp-transparent ytp-exp-bottom-control-flexbox ytp-modern-caption ytp-exp-ppp-update ytp-cairo-refresh ytp-livebadge-color-control ytp-cairo-refresh-signature-moments ytp-bigboards ytp-large-width-mode ytp-fine-scrubbing-exp ytp-fit-cover-video ytp-hide-info-bar ytp-heat-map-v2 ytp-heat-map ytp-ce-shown ytp-iv-drawer-enabled ytp-autonav-endscreen-cancelled-state playing-mode ytp-branding-shown ytp-autohide\" id=\"movie_player\" data-version=\"\/s\/player\/b46bb280\/player_ias.vflset\/en_US\/base.js\" aria-label=\"YouTube Video Player\">\r\n<div class=\"ytp-chrome-bottom\" data-layer=\"9\">\r\n<div class=\"ytp-chrome-controls\">\r\n<div class=\"ytp-left-controls\"><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"below\" class=\"style-scope ytd-watch-flexy\">\r\n<div id=\"limited-state\" class=\"attached-message style-scope ytd-watch-flexy\"><span style=\"text-align: initial;font-size: 1em\">Watch the Interactive video on the process of digestion and absorption<\/span><\/div>\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<span>[h5p id=\"63\"]<\/span>\r\n\r\nExplore the image hotspot to know about the digestive system\r\n\r\n<span>[h5p id=\"64\"]<\/span>\r\n\r\nDrag and Drop thereby label the parts of the Digestive system\r\n\r\n<span>[h5p id=\"65\"]<\/span>\r\n\r\nTest your knowledge about the digestive system\r\n\r\n<span>[h5p id=\"66\"]<\/span>","rendered":"<h1>Digestion<\/h1>\n<p><span>Digestion is the mechanical and chemical break down of food into small organic fragments. During the process of digestion large complex\u00a0\u00a0<\/span><span>proteins, polysaccharides, and lipids molecules are reduced to simple molecules\u00a0 such as simple sugar, acids acids and fatty acids\u00a0 before they can be absorbed by the intestinal epithelial cells.\u00a0<\/span><\/p>\n<h3>Main Organs of the Digestive System<\/h3>\n<p><img decoding=\"async\" src=\"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/a\/a7\/Digestive-system-for-kids.png\/398px-Digestive-system-for-kids.png?20140510192231\" alt=\"File:Digestive-system-for-kids.png\" class=\"aligncenter\" \/><\/p>\n<p style=\"text-align: center\"><a href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Digestive-system-for-kids.png\" target=\"_blank\" rel=\"noopener\">&#8220;Digestive-system&#8221;<\/a><span>\u00a0by\u00a0<\/span><a>Leysi24 via Wikimedia commons<\/a><a><\/a><a><\/a><span>\u00a0is licensed under\u00a0<\/span><a href=\"http:\/\/creativecommons.org\/licenses\/by\/3.0\" target=\"_blank\" rel=\"noopener\">CC BY 3.0<\/a><\/p>\n<ol>\n<li><strong>Mouth<\/strong>: Digestion of food\u00a0 begins in the mouth. The food is chewed and mixed with saliva in the mouth so as to break it down into a form that can be easily swallowed and digested.<\/li>\n<li><strong>Esophagus<\/strong>: It is the muscular tube that connects the mouth to the stomach. The food\u00a0 moves from the mouth through\u00a0 esophagus by a wave-like muscle contraction process called\u00a0<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_244_910\"> peristalsis<\/a>\u00a0 .<\/li>\n<li><strong>Stomach<\/strong>: The food is further broken down in the stomach\u00a0 using stomach acids and enzymes.\u00a0 The food is now turned into a semi-liquid form called<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_244_912\"> chyme<\/a>.T<span>he stomach links the esophagus to the duodenum. The empty stomach is only about the size of\u00a0 fist, but can stretch to hold as much as 4 liters of food and fluid,\u00a0 and then return to its resting size when empty. There are four main regions in the\u00a0stomach: the <strong>cardia, fundus, body, and pylorus.<\/strong><\/span>\n<ul>\n<li><span>The\u00a0<\/span><span data-type=\"term\">cardia<\/span><span>\u00a0(or cardiac region) : This is the point where the esophagus connects to the stomach and through which food passes into the stomach. <\/span><\/li>\n<li><span>Fundus : is located inferior to the diaphragm, above and to the left of the cardia. It\u00a0 is the dome-shaped <\/span><span>. <\/span><\/li>\n<li><span>Body : This is <\/span><span>\u00a0the main part of the stomach and is located below the fundus. <\/span><\/li>\n<li><span>Pylorus : This is\u00a0 funnel-shaped. The\u00a0 <\/span><span data-type=\"term\">pylorus<\/span><span> connects the stomach to the duodenum. The wider end of the funnel is called\u00a0 the <\/span><strong>pyloric antrum<\/strong><span><strong>,<\/strong> This\u00a0 connects to the body of the stomach. The narrower end is called the <\/span><strong>pyloric canal<\/strong><span><strong>,<\/strong> which connects to the duodenum. The <\/span><span data-type=\"term\">pyloric sphincter<\/span><span> is located at the bottom of the stomach, between the stomach and the duodenum. It controls stomach emptying. In the absence of food, the stomach deflates inward, and its mucosa and submucosa fall into a large fold called a <\/span><span data-type=\"term\">ruga<\/span><span>.<\/span><\/li>\n<\/ul>\n<\/li>\n<li><strong>Small Intestine<\/strong>: The small intestine includes the the duodenum, jejunum, and ileum. Most of the digestion and absorption of nutrients occurs in the small intestine. It is t<span>he longest part of the alimentary canal, the small intestine is about 3.05 meters (10 feet) long in a living person. The diameter of the small intestine is about 2.54 cm (1 in).The folds and projections of the lining of the small intestine gives\u00a0 an enormous surface area of about\u00a0 200 m<sup>2\u00a0<\/sup><\/span><\/li>\n<li><strong>Large Intestine<\/strong>: The large intestine <span> runs from the appendix to the anus and <\/span>includes the cecum, colon, and rectum. The water and salts from the material that has not been digested are absorbed in the large intestine. The large intestine\u00a0 is responsible for forming and expelling feces. The large intestine frames the small intestine on three sides and has a\u00a0 diameter more than twice of the small intestine, about 3 inches. <span>The ileocecal valve, located at the opening between the ileum and the large intestine. It controls the flow of chyme from the small intestine to the large intestine. The cecum is a sac-like structure that is suspended inferior to the ileocecal valve. It is about 6 cm (2.4 in) long. It\u00a0 receives the contents of the ileum, and continues the absorption of water and salts. Attached to the cecum is the appendix (or vermiform appendix) which is a winding tube . The 7.6-cm (3-in) long appendix contains lymphoid tissue, suggesting an immunologic function. The cecum blends seamlessly with the colon. On the right side of the abdomen, the food residue initially passes through the ascending colon. The colon becomes the transverse colon at the inferior surface of the liver, where it bends to form the right colic flexure (hepatic flexure).The final third of the transverse colon marks the start of the area known as the hindgut. After passing through the transverse colon, food waste reaches the left side of the abdomen, where it reaches the left colic flexure (splenic flexure), where the colon angles abruptly just inferior to the spleen. From there, food residue goes through the descending colon, which runs down the left side of the posterior abdominal wall. It becomes the s-shaped sigmoid colon after entering the pelvis .Food residue leaving the sigmoid colon enters the\u00a0rectum\u00a0in the pelvis, near the third sacral vertebra. The final 20.3 cm (8 in) of the alimentary canal, the rectum extends anterior to the sacrum and coccyx.\u00a0<\/span><\/li>\n<li><strong>Anus<\/strong>: This is the\u00a0 final part of the digestive tract. Anus expels feces\u00a0 from the body. T<span>he anal canal is located in the perineum and is\u00a0 completely outside of the abdominopelvic cavity. This 3.8\u20135 cm (1.5\u20132 in) long structure opens to the exterior of the body at the anus. The anal canal has two sphincters namely\u00a0 the internal anal sphincter\u00a0 and the external sphincter .The internal 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.\u00a0 Both the sphincters usually remain closed except when defecating.<\/span><\/li>\n<\/ol>\n<h3>Accessory Organs of the digestive system<\/h3>\n<ol>\n<li><strong>Liver<\/strong>: The bile is produced in the liver\u00a0 which helps digest fats.<\/li>\n<li><strong>Gallbladder<\/strong>: The bile produced in the liver is stored and concentrated in the Gall bladder from where it is released\u00a0 into the small intestine.<\/li>\n<li><strong>Pancreas<\/strong>: Produces digestive enzymes and bicarbonate, which are released into the small intestine to aid in digestion.<\/li>\n<\/ol>\n<h3>Phases of Digestion<\/h3>\n<ol>\n<li><strong>Cephalic Phase<\/strong>: Triggered by the sight, smell, or thought of food, stimulating saliva and digestive juices.<\/li>\n<li><strong>Gastric Phase<\/strong>: Begins when food enters the stomach, stimulating the release of gas<\/li>\n<li><strong>Intestinal Phase:<\/strong> Starts when chyme enters the small intestine, triggering the release of digestive enzyme and bile<\/li>\n<\/ol>\n<div class=\"scroller-positioner\">\n<div class=\"content\">\n<div class=\"main\" id=\"cib-chat-main\" role=\"feed\">\n<div class=\"message\">\n<div class=\"content user-select-text\" aria-label=\"Sent by Copilot: The digestion of carbohydrates, proteins, and fats involves specific enzymes and processes that break down these macronutrients into their absorbable forms. Here's a detailed look at each: ### Carbohydrate Digestion 1. **Mouth**: Digestion begins with salivary amylase in the saliva, which breaks down starches into maltose and dextrins. 2. **Stomach**: Carbohydrate digestion pauses in the acidic environment of the stomach. 3. **Small Intestine**: Pancreatic amylase continues the breakdown of starches into maltose. Enzymes like maltase, sucrase, and lactase on the intestinal brush border convert disaccharides into monosaccharides (glucose, fructose, and galactose). 4. **Absorption**: Monosaccharides are absorbed into the bloodstream through the intestinal lining[^1^][^2^]. ### Protein Digestion 1. **Stomach**: Proteins are denatured by stomach acid (HCl) and broken down into smaller peptides by the enzyme pepsin. 2. **Small Intestine**: Pancreatic enzymes (trypsin, chymotrypsin, and carboxypeptidase) further break down peptides into smaller peptides and amino acids. Brush border enzymes (peptidases) complete the digestion into amino acids. 3. **Absorption**: Amino acids are absorbed into the bloodstream through the intestinal lining[^1^][^2^]. ### Fat Digestion 1. **Mouth**: Minor digestion of fats begins with lingual lipase. 2. **Stomach**: Gastric lipase continues the digestion of fats into smaller droplets. 3. **Small Intestine**: Bile from the liver emulsifies fats, increasing the surface area for pancreatic lipase to act. Pancreatic lipase breaks down triglycerides into monoglycerides and free fatty acids. 4. **Absorption**: Monoglycerides and fatty acids form micelles, which are absorbed into the intestinal cells. Inside the cells, they are reassembled into triglycerides and packaged into chylomicrons, which enter the lymphatic system and then the bloodstream[^1^][^2^][^3^]. Would you like more information on any specific part of these processes or how they are regulated?\">\n<div class=\"ac-container ac-adaptiveCard\">\n<div class=\"ac-textBlock\">\n<h3>Carbohydrate Digestion<\/h3>\n<ol>\n<li><strong>Mouth<\/strong>: Digestion begins with salivary amylase in the saliva, which breaks down starches into maltose and dextrins.<\/li>\n<li><strong>Stomach<\/strong>: Carbohydrate digestion pauses in the acidic environment of the stomach.<\/li>\n<li><strong>Small Intestine<\/strong>: Pancreatic amylase continues the breakdown of starches into maltose. Enzymes like maltase, sucrase, and lactase on the intestinal brush border convert disaccharides into monosaccharides (glucose, fructose, and galactose).<\/li>\n<li><strong>Absorption:<\/strong> Monosaccharides are absorbed into the bloodstream through the intestinal lining<\/li>\n<\/ol>\n<h3>Protein Digestion<\/h3>\n<ol>\n<li><strong>Stomach<\/strong>: Proteins are denatured by stomach acid (HCl) and broken down into smaller peptides by the enzyme pepsin.<\/li>\n<li><strong>Small Intestine<\/strong>: Pancreatic enzymes (trypsin, chymotrypsin, and carboxypeptidase) further break down peptides into smaller peptides and amino acids. Brush border enzymes (peptidases) complete the digestion into amino acids.<\/li>\n<li><strong>Absorption:<\/strong> Aminoacids are absorbed into the bloodstream through the intestinal lining<\/li>\n<\/ol>\n<h3>Fat Digestion<\/h3>\n<ol>\n<li><strong>Mouth<\/strong>: Minor digestion of fats begins with lingual lipase.<\/li>\n<li><strong>Stomach<\/strong>: Gastric lipase continues the digestion of fats into smaller droplets.<\/li>\n<li><strong>Small Intestine<\/strong>: Bile from the liver emulsifies fats, increasing the surface area for pancreatic lipase to act. Pancreatic lipase breaks down triglycerides into monoglycerides and free fatty acids.<\/li>\n<li><strong>Absorption<\/strong>: Monoglycerides and fatty acids form micelles, which are absorbed into the intestinal cells, where they are reassembled in to triglycerides and are packaged into chylomicrons which then enter the lymphatic system and then the blood stream.<\/li>\n<\/ol>\n<div class=\"textbox shaded\"><a href=\"https:\/\/youtu.be\/2uL4b1yMhm8?si=_foOGHX_-xid-S2v\">Watch the video <span style=\"text-align: initial;font-size: 1em\">Human Digestive System| Middle School Science | Khan Academy<\/span><\/a><\/div>\n<p>&nbsp;<\/p>\n<div id=\"player\" class=\"style-scope ytd-watch-flexy\">\n<div id=\"player-container-outer\" class=\"style-scope ytd-watch-flexy\">\n<div id=\"player-container-inner\" class=\"style-scope ytd-watch-flexy\">\n<div id=\"player-container\" role=\"complementary\" class=\"style-scope ytd-watch-flexy\">\n<div id=\"container\" class=\"style-scope ytd-player\">\n<div class=\"html5-video-player ytp-transparent ytp-exp-bottom-control-flexbox ytp-modern-caption ytp-exp-ppp-update ytp-cairo-refresh ytp-livebadge-color-control ytp-cairo-refresh-signature-moments ytp-bigboards ytp-large-width-mode ytp-fine-scrubbing-exp ytp-fit-cover-video ytp-hide-info-bar ytp-heat-map-v2 ytp-heat-map ytp-ce-shown ytp-iv-drawer-enabled ytp-autonav-endscreen-cancelled-state playing-mode ytp-branding-shown ytp-autohide\" id=\"movie_player\" data-version=\"\/s\/player\/b46bb280\/player_ias.vflset\/en_US\/base.js\" aria-label=\"YouTube Video Player\">\n<div class=\"ytp-chrome-bottom\" data-layer=\"9\">\n<div class=\"ytp-chrome-controls\">\n<div class=\"ytp-left-controls\">\n<div class=\"textbox shaded\">\n<div class=\"style-scope ytd-watch-flexy\">\n<div class=\"style-scope ytd-watch-flexy\">\n<div class=\"style-scope ytd-watch-flexy\">\n<div role=\"complementary\" class=\"style-scope ytd-watch-flexy\">\n<div class=\"style-scope ytd-player\">\n<div class=\"html5-video-player ytp-transparent ytp-exp-bottom-control-flexbox ytp-modern-caption ytp-exp-ppp-update ytp-cairo-refresh ytp-livebadge-color-control ytp-cairo-refresh-signature-moments ytp-bigboards ytp-large-width-mode ytp-fine-scrubbing-exp ytp-fit-cover-video ytp-hide-info-bar ytp-heat-map-v2 ytp-heat-map ytp-ce-shown ytp-iv-drawer-enabled ytp-autonav-endscreen-cancelled-state playing-mode ytp-branding-shown ytp-autohide\" data-version=\"\/s\/player\/b46bb280\/player_ias.vflset\/en_US\/base.js\" aria-label=\"YouTube Video Player\">\n<div class=\"ytp-chrome-bottom\" data-layer=\"9\">\n<div class=\"ytp-chrome-controls\">\n<div class=\"ytp-left-controls\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"below\" class=\"style-scope ytd-watch-flexy\">\n<div id=\"limited-state\" class=\"attached-message style-scope ytd-watch-flexy\"><span style=\"text-align: initial;font-size: 1em\">Watch the Interactive video on the process of digestion and absorption<\/span><\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p><span><\/p>\n<div id=\"h5p-63\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-63\" class=\"h5p-iframe\" data-content-id=\"63\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"The digestive tract-interactive video\"><\/iframe><\/div>\n<\/div>\n<p><\/span><\/p>\n<p>Explore the image hotspot to know about the digestive system<\/p>\n<p><span><\/p>\n<div id=\"h5p-64\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-64\" class=\"h5p-iframe\" data-content-id=\"64\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"DIGESTIVE SYSTEM\"><\/iframe><\/div>\n<\/div>\n<p><\/span><\/p>\n<p>Drag and Drop thereby label the parts of the Digestive system<\/p>\n<p><span><\/p>\n<div id=\"h5p-65\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-65\" class=\"h5p-iframe\" data-content-id=\"65\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"DIGESTIVE SYSTEM - DRAG AND DROP\"><\/iframe><\/div>\n<\/div>\n<p><\/span><\/p>\n<p>Test your knowledge about the digestive system<\/p>\n<p><span><\/p>\n<div id=\"h5p-66\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-66\" class=\"h5p-iframe\" data-content-id=\"66\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Digestive System 11.3C\"><\/iframe><\/div>\n<\/div>\n<p><\/span><\/p>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_244_910\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_244_910\"><div tabindex=\"-1\"><p>Wave like muscle contraction by which the food moves through the esophagus.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_244_912\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_244_912\"><div tabindex=\"-1\"><p>The semi liquid form of the  food after digestion by stomach acids and enzymes   <\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":1,"menu_order":3,"template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"pb_show_title":"on","pb_short_title":"Digestion","pb_subtitle":"Digestion","pb_authors":["malathi"],"pb_section_license":"cc-by-sa"},"chapter-type":[],"contributor":[62],"license":[54],"class_list":["post-244","chapter","type-chapter","status-publish","hentry","contributor-malathi","license-cc-by-sa"],"aioseo_notices":[],"part":34,"_links":{"self":[{"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/chapters\/244","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":33,"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/chapters\/244\/revisions"}],"predecessor-version":[{"id":2108,"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/chapters\/244\/revisions\/2108"}],"part":[{"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/parts\/34"}],"metadata":[{"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/chapters\/244\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/wp\/v2\/media?parent=244"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/pressbooks\/v2\/chapter-type?post=244"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/wp\/v2\/contributor?post=244"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/wp-json\/wp\/v2\/license?post=244"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}