![]() ![]() These structures of the small intestine are destined to assist and enhance the absorption of water and nutrients by providing increased surface area. The wall of the small intestine known as mucosa made up of simple columnar epithelium covered by folds is a permanent feature with finger-like projections known as villi or microvilli. The food reaches the blood vessels present in the small intestine's wall to get all nutrients to be absorbed here. Active transport is the method of absorption of the nutrients in the small intestine with the help of an energy carrier along the concentration gradient. The small intestine is the region where digested food reaches for absorption through the process known as active transport or diffusion mechanism. The small intestine has three parts which are known as the duodenum present as the first section, jejunum as the middle section, and ileum as the final section. ![]() It does not store any personal data.The small intestine is a part of the digestive system with variable size depending upon the individual height, taller the height longer the small intestine, and the shorter the height smaller the small intestine. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. Fig 2 - The sodium-amino acid transporter, which is nearly identical to the sodium-glucose transporter. In this article, we will look at the digestion and absorption of carbohydrates, protein and lipids. Absorption refers to the movement of nutrients, water and electrolytes from the lumen of the small intestine into the cell, then into the blood. ![]() The chylomicrons are too large to enter circulation, so they enter lymphatic system via lacteals.ĭigestion is the chemical breakdown of the ingested food into absorbable molecules. The lipids are then packaged inside apoproteins to form a chylomicron. Inside the cell, the products are re-esterified to form the original lipids, triglycerides, cholesterol and phospholipids. The products from digestion are released at the apical membrane and diffuse into the enterocyte. Pancreatic lipase, phospholipase A2 and cholesterol ester hydrolase (3 major enzymes involved in lipid digestion) hydrolyse the micelles, breaking them down into fatty acids, monoglycerides, cholesterol and lysolecithin. Here, bile aids digestion by emulsifying the fat goblets into smaller chunks, called micelles, which have a much larger surface area. The remainder of the lipids are digested in the small intestine. Their digestion is started by lingual and gastric lipases, but this only digests 10% of ingested lipids. Lipids are hydrophobic, and thus are poorly soluble in the aqueous environment of the digestive tract. Fructose enters the cell by facilitated diffusion via GLUT5 and is transported into the blood via GLUT2 receptors. ![]() Both glucose and galactose exit the cell via GLUT2 receptors across the basolateral membrane into the blood. Glucose and galactose are absorbed across the apical membrane by secondary active transport (along with Na +) through the Sodium-Glucose cotransporter ( SGLT1). Brush border enzymes (lactase, sucrase, trehalase) hydrolyse these compounds into molecules of glucose, galactose and fructose. The disaccharides produced (maltose, maltotriose, and α-dextrins) are all converted to glucose by brush border enzymes.ĭisaccharides occurring naturally in food do not require amylase to break them down. The main enzyme is pancreatic amylase, which yields disaccharides from starch by digesting the alpha 1-4 glycosidic bonds. The majority of carbohydrate digestion occurs in the small intestine. There are three carbohydrate products which are absorbed by the small intestine glucose, galactose and fructose.ĭigestion of starch is initiated in the mouth, facilitated by salivary amylase. ![]()
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