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Understanding Digestion Process: Key Steps for Nutrient Absorption

Learn about the process of digestion, from breaking down nutrients to absorption, including physical and chemical digestion. Discover how food is prepared for absorption through mechanical breakdown and enzyme catalysis in the mouth, esophagus, stomach, and intestines.

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Understanding Digestion Process: Key Steps for Nutrient Absorption

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  1. DIGESTION The process of preparing your food for absorption http://www.mhhe.com/cgi-bin/netquiz_get.pl?qfooter=/usr/web/home/mhhe/biosci/genbio/animation_quizzes/animate_30fq.htm&afooter=/usr/web/home/mhhe/biosci/genbio/animation_quizzes/animate_30fa.htm&test=/usr/web/home/mhhe/biosci/genbio/animation_quizzes/animate_

  2. What Happens to the Food We Eat?

  3. Digestion • To break nutrients into smaller molecules • Physical Digestion • Mechanical breakdown of food particles • Chemical Digestion • Enzyme catalyzed breakdown of nutrient molecules

  4. Absorption • Movement of digested nutrients through intestinal wall into: • Blood (water soluble nutrients) • Lymphatic system - > blood (fat soluble nutrients

  5. Digestion:The Mouth • Chewing: physically breaks down food into smaller components • Food stimulates salivary glands to release saliva • Saliva contains amylase-breaks down starch • Saliva moistens food for easy swallow • Bolus: ball of chewed food mixed with saliva

  6. DIGESTION:THE PHARYNX • Area responsible for swallowing • During swallowing, air passage is blocked by epiglottis • Blocks the food from entering the trachea and the lungs • Bolus is directed down the esophagus

  7. DIGESTION:THE ESOPHAGUS • Connects the pharynx and the stomach • Bolus is moved towards the stomach by a contractile movement called peristalsis • Allows food to move through thoracic cavity, through diaphragm, to peritoneal cavity and the stomach (peristalsis)

  8. Digestion: Chewing

  9. Digestion: Swallowing

  10. Digestion: Swallowing

  11. DIGESTION:THE STOMACH • Food passes through a sphincter, (esophageal sphincter) a valve • Bolus mixes with stomach secretions to become chyme • HCl denatures proteins and kills bacteria • Mucus protects stomach wall from acid • Chyme released into small intestine through pyloric sphincter

  12. DIGESTION:STOMACH • Stops salivary amylase and and slows lingual lipase activity (acid denatures enzyme) • Starts protein digestion: pepsin activated and starts protein digestion • Two Australians win Nobel Prize in medicine - More Health News - MSNBC.com

  13. Digestion: The Stomach

  14. DIGESTION:SMALL INTESTINE • 20 feet in length • divided into three segments: • duodenum • jejunum • ileum • 95% of digestion occurs in small intestine • Bile: made in liver, stored in gall bladder • Emulsifies fats

  15. Digestion: Accessory Organs

  16. Absorption

  17. DIGESTION:SMALL INTESTINES • Pancreas: • Secretes bicarbonate into duodenum to neutralize stomach acid in the chyme • Secretes enzymes that act on • protein (proteases) • carbohydrate (carbohydrases) • lipids (lipases)

  18. DIGESTION:LARGE INTESTINES • Absorbs water and some minerals • Supports growth of bacteria that produce Vitamin K • Supports growth of other bacteria that partially breaks down fiber • We are then able to absorb some of the breakdown products

  19. Absorption and Transportation • All nutrients must pass through intestinal lining • Picked up by capillaries or lymphatic vessels

  20. DIGESTION:CARBOHYDRATES • Begins in the mouth: salivary amylase • Amylase denatured in stomach • Small intestine: pancreatic enzymes breakdown large CHO’s(starch) to smaller • Small intestines: brush border cells produce disaccharidases (sucrase, maltase, lactase) • Breakdown sucrose, maltose, lactose • Absorption occurs in duodenum & jejunum

  21. DIGESTION:PROTEIN • Protein digestion begins in the stomach • Denaturation by HCl • Pepsin breaks large proteins into smaller peptides • Pancreatic enzymes introduced into the duodenum • Break down peptides into amino acids, di- and tri-peptides • Intestine enzymes breakdown to amino acids

  22. DIGESTION:LIPIDS • Mouth: Lingual Lipase, very little activity • Stomach: very little activity • Small Intestines: Major activity • Bile from gall bladder emulsifies • Enzymes from pancreas digest and makes the products ready for digestion • monoglycerides, glycerol, fatty acids • absorbed into cells of microvilli

  23. Other Systems • Cardiovascular • Hormonal and Nervous • Storage • Liver • Muscle • Fat

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