Digestion How do we get energy in Ingestion Digestion and Absorption all accomplished through the gastrointestinal tract Lipids Carbohydrates and Proteins We need more than just calories Minerals Required by Humans Gut Organization Regional Roles Earthworm Mouth Esophagus Grasshopper Stomach Large intestine Small intestine Human Foregut mouth stomach Midgut small intestine Hindgut large intestine anus Dog Ingestion digestion absorption storage and expulsion Ingestion get it in and keep it moving Digestion all processes that prepare for absorption Mechanical processes Break down inc SA V Mix up Move along Chemical processes are completed by enzymes and require high SA Absorption Expulsion Salivary amylase carbohydrates Salivary lipase lipids Movement of Food Autonomic NS 1 Rhythmic muscular contraction and relaxation peristalsis moves food downward Peristalsis occurs throughout the GI tract 2 Food leaving the stomach passes through the pyloric sphincter a band of muscle at the base of the stomach that opens and closes to regulate the rate at which the stomach empties 3 Churning of food in the stomach and small intestines ensures mixing and increases chemical digestion Into the Stomach we go Stomach pH 1 Stomach enzymes act at a low pH of 1 5 3 a Antimicrobial b Denature proteins 2 Cells lining the stomach secrete HCl to maintain low pH 3 Gastrin secreted when food arrives stimulates the production of more HCl and pepsinogen Stomach Digestive Enzymes 1 Pepsin breaks down protein into amino acids Lipases break down lipids 2 3 Notice no new chemical breakdown of carbs 4 The stomach stores food as well as digests it Fig 41 12 m 5 Interior surface of stomach Gastric gland Mucus cells Chief cells Parietal cells Esophagus Sphincter Stomach Sphincter Small intestine Epithelium Pepsinogen Pepsin 3 2 HCl 1 H Cl Folds of epithelial tissue 1 2 3 Pepsinogen and HCl are secreted HCl converts pepsinogen to pepsin Pepsin activates more pepsinogen Chief cell Parietal cell Cast of characters Carbonic anhydrase H K pump HCO3 Cl antiporter Cl channel K channel Notice the pump transporter and channels Blood vessels Nerve Mesentery Mammalian Small Intestine Nerve net between muscle layers Serosa Longitudinal muscle layer Circular muscle layer Submucosa Mucosa Lumen Duodenum function Liver cut section Bile Common bile duct Stomach cut Liver Large intestine Duodenum Jejunum Ileum Bicarbonate ions Digestive enzymes Pancreas Pancreatic duct Fats in the duodenum stimulate cells lining the duodenum to secrete CCK that in turn stimulates the gallbladder to contract and release stored bile that helps to break down fats Gallbladder CCK FATS Stomach acid Duodenum Lipase Secretin Stomach acid in the duodenum stimulates cells lining the duodenum to release secretin that in turn stimulates the pancreas to release bicarbonate ions to neutralize the acid Stomach acid in the duodenum stimulates cells lining the duodenum to release secretin that in turn stimulates the pancreas to release bicarbonate ions to neutralize the acid Fats in the duodenum stimulate cells lining the duodenum to secrete CCK that in turn stimulates the gallbladder to contract and release stored bile that helps to break down fats DigestiveenzymesBicarbonateionsBileLipaseSecretinCCKStomachacid Endocrine Islets of Langerhans Alpha cells glucagon Beta cells insulin Exocrine via the pancreatic duct Trypsin and chymotrypsin digest protein Amylase digests carbohydrates Lipase digest fats The MIGHTY Pancreas 20 of Villi and Microvilli Glucose Absorption Lumen of small intestine Na Glucose Na glucose co transporter Cytoplasm of intestinal cell K Na K ATPase Glucose transport protein Blood vessel Na Glucose Glucose enters an intestinal cell along with Na driven by the Na concentration difference between the lumen of the intestine and the cytoplasm of the cell Na concentration is kept low inside the cell by the action of the Na K pump Glucose exits the intestinal cell passively by a glucose transport protein Glucose exits the intestinal cell passively by a glucose transport protein Glucose enters an intestinal cell along with Na driven by the Na concentration difference between the lumen of the intestine and the cytoplasm of the cell Na concentration iskept low inside thecell by the action ofthe Na K pump Carbohydrate digestion Protein digestion Nucleic acid digestion Fat digestion Fig 41 13 Oral cavity pharynx esophagus Stomach Polysaccharides starch glycogen Disaccharides sucrose lactose Salivary amylase Smaller polysaccharides maltose Proteins Pepsin Small polypeptides Polypeptides Smaller polypeptides Pancreatic carboxypeptidase Amino acids Small peptides Lumen of small intes tine Polysaccharides Pancreatic amylases Maltose and other disaccharides Pancreatic trypsin and chymotrypsin Pancreatic nucleases DNA RNA Fat globules Bile salts Fat droplets Nucleotides Pancreatic lipase Glycerol fatty acids monoglycerides Epithelium of small intestine brush border Disaccharidases Dipeptidases carboxypeptidase and aminopeptidase Monosaccharides Amino acids Nucleotidases Nucleosides Nucleosidases and phosphatases Nitrogenous bases sugars phosphates Hepatic Portal System Drains Spleen Pancreas GI tract Gallbladder Liver Detox anything harmful Store sugar or send it into circulation Gluconeogenesis Reabsorption of water minerals ions Na Cl Formation storage and expulsion of feces rectum anus Houses bacteria Provide beneficial nutrients and vitamins Cheap protein powder Lactose intolerance Beans Cellulose Appendix what the what Large Intestine Digestion LLOs 1 Know the foregut midgut and hindgut s roles in digesting an animal s diet 2 Know where and how the three macromolecules break down in foregut and midgut and how they are absorbed into the body 3 Understand the necessity of a strongly acidic stomach and how protein digestion occurs within the stomach 4 Describe how the stomach creates and maintains an acidic stomach 5 Describe how the small Intestine works with the pancreas and liver to finish digestion and start complete absorption 6 Know that the large intestine retains digesta long enough to absorb water and nutrients before expulsion