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Intestines and accessory organs Small Intestine The small intestine (5.75m) is a long tube where the majority of food digestion and absorption takes place Small Intestine The small intestine (5.75m) is a long tube where the majority of food digestion and absorption takes place Chemical digestion is completed and nutrients are absorbed into the blood stream in the small intestine The chyme is pushed through the stomach via peristaltic motions of the stomach wall The chyme enters the small intestine when pyloric sphincter relaxes (remember the cardiac sphincter is the entrance to the stomach and pyloric sphincter is the exit) Small Intestine – 3 parts Duodenum (25cm) - The receiving area for chemicals and food from the stomach. This structure receives the barrage of enzyme cocktails from a variety of accessory digestive organs. Jejunum (2.5m) – the location where most of the nutrients are absorbed into the blood. Ileum (3m) - Remaining nutrients are absorbed at this point before moving into the large intestine. Small Intestine – Build for Effeciency •The small intestine has finger-like extensions of the mucosa called villi •Villi then have further folds called microvilli What is the advantage of villi and microvilli? … to maximize surface area Villi Finger like projections Each villus contains capillaries and a lymph vessel Products of fat digestion enter here Microvilli Projections on villi Quiz quiz quiz … The amino acids, glucose, glycerol and fatty acids are mostly absorbed in which section of the small intestine? Duodenum Jejunum Ileum Nutrients that are absorbed include: - Amino acids - Nucleotides - Fatty acids - Monosaccharide - Vitamins (very little) - Minerals (very little) http://kidvideos.blogspot.com/2006/09/digestion-video.html Nutrients are broken down into monomers … Polysaccharides to monosaccharides Nucleic acids to Nucleotides Proteins to amino acids Large Intestine Consists of caecum, colon, rectum and anus Function of colon is to reabsorb water, salts, and some vitamins and minerals Colon also accumulates and prepares waste Lots of bacteria ferment cellulose Vitamin B and K are synthesized Appendix is found in the ileocecal valve Rectum Feces are held here until a socially acceptable time Two sphincter muscles Voluntary Involuntary Anus – where feces are eliminated The following all mean the same thing: Alimentary canal/ Gastrointestinal Tract/Digestive Tract = Mouth to Anus Accessory Organs – scavenger hunt There are 3 key accessory organs that we haven’t discussed yet – please use pages 216-224 of your text to find the answers to the following: How are the cells of the small intestine protected from stomach acid? What does the pancreas secrete to neutralize HCL? What does an increase in pH of the small intestine do? The pancreas also secretes enzymes called lipases, proteases, amylases, and nucleases into the small intestine – what do you think each of these does? What are the functions of the liver? What is bile? How does the liver know when to secrete bile? What are gallstones? What does the liver do with excess glucose? If blood sugar was low what would the liver do to help with this problem? Liver Liver is second largest organ in the body major functions: - secretion of bile - “cleans” the blood extract nutrients and toxins (disposed of via catalase) - Most products of digestion are carried here by the hepatic portal vein - stores excess glucose glycogen, - Helps regulate body metabolism Two lobes Gallbladder Bile Is a mixture of bile salts, bile acids, cholesterol, phospholipids, fatty acids, and water – produce about 1 L a day It is used to emulsify fat into globules & bile salts help in absorption of lipids Gall Bladder Stores bile Secretes it into duodenum (due to cholecystokinin or CKK) Bile emulsifies the fat (similar to soap) * Fat enters duodenum endocrine cells secrete hormone cholecystokinin (CKK) into blood CKK causes gallbladder to contract and send bile through the bile duct to duodenum What are these and what happened to them?? Pancreas Specialized for secretion Chyme is slightly acidic when it enters the duodenum causes a release of the hormone secretin from duodenal walls Secretin is absorbed into bloodstream and travels to pancreas signals release of bicarbonate ions to neutralize acid and increase alkalinity of duodenum pH 9 causes enzyme pepsin to become inactive Pancreas Pancreatic fluid is secreted into the duodenum Nuclease Nucleic acids into nucleotides Proteases Polypeptides into amino acids Amylases Polysac into glucose (monosac) Lipases Lipids (triglycerides) into fatty acids and glycerol Releases sodium bicarbonate, which neutralizes the acidic stomach contents. Pancreas Releases Hormones Insulin Cause uptake of glucose into cells And storage into glycogen Glucagon Causes release of glucose from liver glycogen Regulating Blood Sugar Homeostasis Diabetes http://www.diabetes.ca/about-diabetes/
