Digestive System FST 307 PDF

FST 307 BASIC NUTRITION CHAPTER 2 FATE OF NUTRIENTS IN HUMAN BODY CHAPTER OUTCOMES At the end of this chapter, students should be able to:- a) Explain briefly about the functions of digestive organs. b) Describe the carbohydrate, fat and protein digestion.  DIGESTI...

FST 307 BASIC NUTRITION CHAPTER 2 FATE OF NUTRIENTS IN HUMAN BODY CHAPTER OUTCOMES At the end of this chapter, students should be able to:- a) Explain briefly about the functions of digestive organs. b) Describe the carbohydrate, fat and protein digestion.  DIGESTION  Definition: a) is a process where foodstuffs are broken down into smaller and simpler units b) It also require enzymes to speed up reaction and hormones to control the process  Basic anatomy of the GI tract a) mouth esophagus stomach small intestine large intestine HUMAN DIGESTIVE SYSTEMS If food is not digested and absorbed, it is eliminated; doesn’t provide nutrients DIGESTIVE ORGANS  MOUTH  The mouth is the beginning of the digestive tract  Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a smaller form for body to absorb and use.  Saliva a) Excreted by Salivary glands b) Containing : Water, salts, mucus, enzymes  ESOPHAGUS  Located in throat near trachea  Esophagus receives food from mouth when swallow.  By means of a series of muscular contractions called peristalsis, the esophagus delivers food to stomach  STOMACH  The stomach is a hollow organ, or "container," that holds food while it is being mixed with gastric juice (enzymes, water & HCl) that continue the process of breaking down food into a usable form.  Cells in the lining of the stomach secrete a strong HCl and powerful enzymes that are responsible for the breakdown process.  Goblet cell secrete mucin to form mucus  When the contents of the stomach are sufficiently processed, they are released into the small intestine.  PANCREAS  Pancreas secretes pancreatic juice (enzymes and bicarbonate) into the duodenum, the first segment of the small intestine.  These enzymes break down protein, fats, and carbohydrates.  The pancreas also makes insulin, secreting it directly into the bloodstream. Insulin is the chief hormone for metabolizing sugar.  LIVER  Its main function within the digestive system is to process the nutrients absorbed from the small intestine.  Bile from the liver secreted into the small intestine also plays an important role in digesting fat.  It is the body’s chemical "factory“ where it takes the raw materials absorbed by the intestine and makes all the various chemicals the body needs to function.  The liver also detoxifies potentially harmful chemicals. It breaks down and secretes many drugs.  GALLBLADDER  It stores and concentrates bile, and then releases it into the duodenum to help absorb and digest fats.  SMALL INTESTINE  It is a 22-foot long muscular tube that breaks down food using enzymes released by the pancreas and bile from the liver.  Made up of three segments a) Duodenum - responsible for the continuous breaking down process b) Jejunum - absorption of nutrients into the bloodstream c) Ileum - absorption of nutrients into the bloodstream  Peristalsis is also working in this organ, moving food through and mixing it with digestive secretions from the pancreas and liver.  Contents of the small intestine start out semi-solid, and end in a liquid form after passing through the organ.  Once the nutrients have been absorbed and the leftover-food residue liquid has passed through the small intestine, it then moves on to the large intestine, or colon.  LARGE INTESTINE  The colon is a 6-foot long muscular tube that connects the small intestine to the rectum.  The large intestine is made up of the cecum (pronounce “seh- kum”), the ascending (right) colon, the transverse (across) colon, the descending (left) colon, and the sigmoid colon, which connects to the rectum.  The appendix is a small tube attached to the cecum.  The large intestine is a highly specialized organ that is responsible for processing waste so that emptying the bowels is easy and convenient. LARGE INTESTINE BILE IN FAT DIGESTION  PAUSE TO PONDER… a) Can you explain briefly about the functions of digestive organs? b) Ask your friend to describe the carbohydrate, fat and protein digestion. CHAPTER OUTCOMES At the end of this chapter, students should be able to:- a) Explain briefly about types of absorption and nutrients transportation. b) Describe briefly about carbohydrate, fat and protein absorption and transportation. NUTRIENTS ABSORPTION  TYPES OF ABSORPTION  Passive a) without carrier or energy expenditure b) [nutrient] in intestine > [nutrient] in absorptive cells c) Water, small lipid and some minerals  Facilitative a) need a carrier molecule but no energy expenditure b) [nutrient] in intestine > [nutrient] in absorptive cells c) WSV & fructose  Active a) need a carrier molecule and energy (ATP) b) [nutrient] in intestine < [nutrient] in absorptive cells c) glucose, galactose, amino acids, others  Phagocytosis/pinocytosis a) phagocytosis "cell eating" b) pinocytosis "cell drinking" c) absorptive cells engulf compounds or liquid d) ex. infant absorbs antibodies from mother's milk ABSORPTION NUTRIENTS TRANSPORTATION  LIPID TRANSPORT a) Lipoproteins – particles containing a core of lipids surrounded by a shell of protein and phospholipid. b) Classification of lipoprotein: i. Chylomicrons ii. VLDL = very-low-density lipoproteins iii. LDL = low-density lipoproteins iv. HDL = high-density lipoproteins  LIPOPROTEINS AND HEALTH  LDL vs. HDL  Vitamins are absorbed primarily in the small intestine  Fat-soluble vitamins are absorbed along with fats and transported in lipoproteins  Some water-soluble vitamins require active transport, or special carrier molecules for absorption  Some vitamins are absorbed as an inactive provitamin, which is converted to the active form in the body DIGESTION & ABSORPTION FLOW OF A SANDWISH NUTRIENTS ABSORPTION  PAUSE TO PONDER… a) Please explain briefly about types of absorption and nutrients transportation. b) Describe briefly about carbohydrate, fat and protein absorption and transportation.  END OF CHAPTER 2 FATE OF NUTRIENTS IN HUMAN BODY