How Is Each Type Of Nutrient Is Absorbed By The Small Intestine.

Absorption from Small Intestine [Author Name(s), First M. Last, Omit Titles and Degrees] [Institutional Affiliation(s)]

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Absorption from the Small Intestine

All the dietary intakes of a human body are absorbed in the small intestine, be it simple lipids, carbs, proteins or minerals like vitamins A, Vitamin K, etc. ADDIN ZOTERO_ITEM CSL_CITATION {"citationID":"Ka6haDiN","properties":{"formattedCitation":"(Smith & Morton, 2011)","plainCitation":"(Smith & Morton, 2011)","noteIndex":0},"citationItems":[{"id":"gH5f1quO/6pPt0pws","uris":["http://zotero.org/users/local/9FPdQOCJ/items/YU2LBHJP"],"uri":["http://zotero.org/users/local/9FPdQOCJ/items/YU2LBHJP"],"itemData":{"id":59,"type":"book","title":"The Digestive System: Systems of the Body Series","publisher":"Elsevier Health Sciences","number-of-pages":"226","source":"Google Books","abstract":"This is an integrated textbook on the digestive system, covering the anatomy, physiology and biochemistry of the system, all presented in a clinically relevant context appropriate for the first two years of the medical student course.One of the seven volumes in the Systems of the Body series.Concise text covers the core anatomy, physiology and biochemistry in an integrated manner as required by system- and problem-based medical courses.The basic science is presented in the clinical context in a way appropriate for the early part of the medical course.","ISBN":"978-0-7020-4841-8","note":"Google-Books-ID: bbzHAAAAQBAJ","title-short":"The Digestive System","language":"en","author":[{"family":"Smith","given":"Margaret E."},{"family":"Morton","given":"Dion G."}],"issued":{"date-parts":[["2011",11,18]]}}}],"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"} (Smith & Morton, 2011). Everything gets absorbed into the blood plasma. Unsurprisingly, the walls of the intestine are highly specialized. They are made up of specialized epithelial cells that have tiny root hair-like structures called microvilli ADDIN ZOTERO_ITEM CSL_CITATION {"citationID":"zP4noPV1","properties":{"formattedCitation":"(Pappenheimer & Michel, 2003)","plainCitation":"(Pappenheimer & Michel, 2003)","noteIndex":0},"citationItems":[{"id":"gH5f1quO/6w4nSzzu","uris":["http://zotero.org/users/local/9FPdQOCJ/items/2YLRGT69"],"uri":["http://zotero.org/users/local/9FPdQOCJ/items/2YLRGT69"],"itemData":{"id":114,"type":"article-journal","title":"Role of villus microcirculation in intestinal absorption of glucose: coupling of epithelial with endothelial transport","container-title":"The Journal of Physiology","page":"561-574","volume":"553","issue":"Pt 2","source":"PubMed Central","abstract":"Capillaries in jejunal villi can absorb nutrients at rates several hundred times greater (per gram tissue) than capillaries in other tissues, including contracting skeletal muscle and brain. We here present an integrative hypothesis to account for these exceptionally large trans-endothelial fluxes and their relation to epithelial transport. Equations are developed for estimating concentration gradients of glucose across villus capillary walls, along paracellular channels and across subjunctional lateral membranes of absorptive cells. High concentrations of glucose discharged across lateral membranes to subjunctional intercellular spaces are delivered to abluminal surfaces of villus capillaries by convection-diffusion in intercellular channels without significant loss of concentration. Post-junctional paracellular transport thus provides the series link between epithelial and endothelial transport and makes possible the large trans-endothelial concentration gradients required for absorption to blood. Our analysis demonstrates that increases of villus capillary blood flow and permeability-surface area product (PS) are essential components of absorptive mechanisms: epithelial transport of normal digestive loads could not be sustained without concomitant increases in capillary blood flow and PS. The low rates of intestinal absorption found in anaesthetised animals may be attributed to inhibition of normal villus microvascular responses to epithelial transport.","DOI":"10.1113/jphysiol.2003.043257","ISSN":"0022-3751","note":"PMID: 12937296\nPMCID: PMC2343570","title-short":"Role of villus microcirculation in intestinal absorption of glucose","journalAbbreviation":"J Physiol","author":[{"family":"Pappenheimer","given":"J R"},{"family":"Michel","given":"C C"}],"issued":{"date-parts":[["2003",12,1]]}}}],"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"} (Pappenheimer & Michel, 2003). These hair-like projections tend to increase the surface area of the cells and the small intestine to facilitate the absorption of a large number of nutrients.

Each villus has a network of small capillaries and lymphatic vessels known as the lacteals, present in its vicinity ADDIN ZOTERO_ITEM CSL_CITATION {"citationID":"zP4noPV1","properties":{"formattedCitation":"(Pappenheimer & Michel, 2003)","plainCitation":"(Pappenheimer & Michel, 2003)","noteIndex":0},"citationItems":[{"id":"gH5f1quO/6w4nSzzu","uris":["http://zotero.org/users/local/9FPdQOCJ/items/2YLRGT69"],"uri":["http://zotero.org/users/local/9FPdQOCJ/items/2YLRGT69"],"itemData":{"id":114,"type":"article-journal","title":"Role of villus microcirculation in intestinal absorption of glucose: coupling of epithelial with endothelial transport","container-title":"The Journal of Physiology","page":"561-574","volume":"553","issue":"Pt 2","source":"PubMed Central","abstract":"Capillaries in jejunal villi can absorb nutrients at rates several hundred times greater (per gram tissue) than capillaries in other tissues, including contracting skeletal muscle and brain. We here present an integrative hypothesis to account for these exceptionally large trans-endothelial fluxes and their relation to epithelial transport. Equations are developed for estimating concentration gradients of glucose across villus capillary walls, along paracellular channels and across subjunctional lateral membranes of absorptive cells. High concentrations of glucose discharged across lateral membranes to subjunctional intercellular spaces are delivered to abluminal surfaces of villus capillaries by convection-diffusion in intercellular channels without significant loss of concentration. Post-junctional paracellular transport thus provides the series link between epithelial and endothelial transport and makes possible the large trans-endothelial concentration gradients required for absorption to blood. Our analysis demonstrates that increases of villus capillary blood flow and permeability-surface area product (PS) are essential components of absorptive mechanisms: epithelial transport of normal digestive loads could not be sustained without concomitant increases in capillary blood flow and PS. The low rates of intestinal absorption found in anaesthetised animals may be attributed to inhibition of normal villus microvascular responses to epithelial transport.","DOI":"10.1113/jphysiol.2003.043257","ISSN":"0022-3751","note":"PMID: 12937296\nPMCID: PMC2343570","title-short":"Role of villus microcirculation in intestinal absorption of glucose","journalAbbreviation":"J Physiol","author":[{"family":"Pappenheimer","given":"J R"},{"family":"Michel","given":"C C"}],"issued":{"date-parts":[["2003",12,1]]}}}],"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"} (Pappenheimer & Michel, 2003). The material and the nutrients come from the food into the small intestine where villi absorb all the essential and required nutrients into the capillaries from the lumen of a small intestine. The amino acids and carbohydrates are absorbed into the blood via the capillaries, while the lacteals take up the lipids. From there, the food is transported and provided to different organs of the body to perform their functions. For example, the absorbed glucose is used to provide energy to perform different metabolic functions of the body and absorbed protein is used to form building blocks of the body. The food that is undigested and unabsorbed is transferred to the large intestine.

It is interesting to note that the essential materials like glucose, amino acids, vitamins, and simple fats that are broken by the enzymes are absorbed into the small intestine by the action of the hormones and certain electrolytes. The jejunum is the part where almost all the major absorption takes place. Nutrients like iron is absorbed in the ilium while the terminal part of the ileum is associated with the absorption of vitamin B12 and Bile salts. Passive diffusion also occurs there, and water and salts are absorbed through this process. Facilitated diffusion also occurs and fructose is absorbed via the same process. Co-transport of amino acid and glucose also occurs. Sodium bicarbonate is absorbed in the intestines with the aid of the active transport mechanism.

References

ADDIN ZOTERO_BIBL {"uncited":[],"omitted":[],"custom":[]} CSL_BIBLIOGRAPHY Pappenheimer, J. R., & Michel, C. C. (2003). Role of villus microcirculation in intestinal absorption of glucose: Coupling of epithelial with endothelial transport. The Journal of Physiology, 553(Pt 2), 561–574. https://doi.org/10.1113/jphysiol.2003.043257

Smith, M. E., & Morton, D. G. (2011). The Digestive System: Systems of the Body Series. Elsevier Health Sciences.