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The Digestive System Marki, Anastasia, and Pritch What’s The Point? • Breaks down food in order to gain three essential things: chemical energy, organic molecules and essential nutrients Chemical Energy • Energy that is in the form of molecular bonds created during photosynthesis • Chemical energy in the form of starches is used in cellular respiration to create ATP Organic Molecules • Organic molecules are used as building blocks within the organism Essential Nutrients • • • • • Four different types: amino acids fatty acids vitamins minerals Amino Acids • Eight essential to humans and a ninth one Histidine is needed by babies • Complete proteins such as meat have all eight • Incomplete proteins such as corn or beans do not have all eight unless eaten together Essential amino acids for adults Methionine Valine Threonine Phenylalanine Leucine Corn (maize) and other grains Isoleucine Tryptophan Lysine Beans and other legumes Fatty Acids • Few that animals cannot synthesize themselves: • linoleic acid is necessary to make membrane phospholipids Vitamins • Organic molecules that perform various functions but cannot be synthesized within the body • Vitamin B2 is FAD+ • Water soluble are B and C, work as coenzymes • Fat soluble A, K, and D work as building blocks Minerals • Inorganic elements • Calcium and phosphorus used in building bones • Iodine in hormones Nourishment • Under-nourishment- body does not have enough chemical energy • Mal-nourishment- body does not have enough of a specific essential nutrient Steps of Eating Small molecules Pieces of food Mechanical digestion Chemical digestion Nutrient (enzymatic hydrolysis) molecules enter body cells Undigested material Food 1 Ingestion 2 Digestion 3 Absorption 4 Elimination Types of Digestive Compartments • Intracellular digestion versus extracellular digestion Intracellular Digestion • By phago or pino cytosis, food is ingested by cells and made into food vacuoles where they can be digested • Occurs in sponges (filter feeders) and single-celled organisms Extracellular Digestion • Gastrovascular cavity: only a mouth • Alimentary canal: mouth and anus Fig. 41-10 Humans have extracellular digestion and an alimentary canal Tongue Sphincter Salivary glands Oral cavity Salivary glands Mouth Pharynx Esophagus Esophagus Sphincter Liver Stomach Ascending portion of large intestine Gallbladder Gallbladder Duodenum of small intestine Pancreas Liver Small intestine Small intestine Large intestine Rectum Anus Appendix Cecum Pancreas Stomach Small intestine Large intestine Rectum Anus A schematic diagram of the human digestive system Cnidaria- exhibit a gastrovascular cavity Main Organs Layers of Tissue Linear Path Salivary glands Mouth Esophagus Gallbladder Liver Pancreas Stomach Small intestine Large intestine Rectum Anus A schematic diagram of the human digestive system Whole Body Ingestion • • • • • • • Mouth Salivary glands that secrete saliva Amylase hydrolyzes starch and glycogen Muchin lubricates mouth and food to avoid abrasion Buffer neutralizes acids Tongue regulates what goes into mouth by taste Bolus, a ball of food, is created and shoved back to the pharynx • Pharynx: (fork between trachea and esophagus) • epiglottis covers glottis opening to trachea Pharynx Ingestion • Esophagus: muscles lining it • Peristalsis- wave-like contractions that push food down in 5-10 seconds • Sphincter- muscular rings in the esophagus that close off parts of the alimentary canal Stomach QuickTime™ and a decompressor are needed to see this picture. Digestion • • • • • Stomach: Gastric Juice : HCL + pepsin Chyme: gastric juice + food Mucus Muscle Digestion • Small intestine (duodenum) • - secretions from pancreas and gall bladder Blood Sugar Homeostasis Stimulus: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level drops below set point. Cecum Small intestine Stomach Small intestine Cecum Colon (large intestine) Carnivore Herbivore Large Intestine • 90% water is recollected • Includes the colon Linear Flow Total Bloodstream Veins to heart Lymphatic system Hepatic portal vein Liver Lipids Stomach Mouth Esophagus Secretions from the gastric glands of the stomach Absorbed food Absorbed (except lipids) water Small intestine Anus Large Rectum intestine Secretions from the pancreas and the liver Final Table Carbohydrate digestion Oral cavity, pharynx, esophagus Protein digestion Nucleic acid digestion Fat digestion Polysaccharides Disaccharides (starch, glycogen) (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Proteins Pepsin Small polypeptides Lumen of small intestine Polysaccharides Pancreatic amylases Polypeptides Pancreatic trypsin and chymotrypsin DNA, RNA Fat globules Pancreatic nucleases Bile salts Maltose and other disaccharides Nucleotides Fat droplets Smaller polypeptides Pancreatic lipase Pancreatic carboxypeptidase Glycerol, fatty acids, monoglycerides Amino acids Epithelium of small intestine (brush border) Small peptides Disaccharidases Monosaccharides Nucleotidases Nucleosides Dipeptidases, carboxypeptidase, and aminopeptidase Amino acids Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Diseases • Crohn’s Disease • Acid Reflux Disease • Celiac Disease Crohn’s Disease • an inflammatory autoimmune disease • Symptoms: primarily abdominal pain, diarrhea (usually with blood), vomiting or weight loss • The immune system attacking the gastrointestinal tract and producing inflammation in the gastrointestinal tract • No cure, but stem cell research is promising • medication to control symptoms, maintain remission and prevent relapses Crohn’s Disease • Affects the ileum and the large intestine or both most commonly • Structuring: narrowing of the bowel which can lead to bowel obstruction or changes in the caliber of feces • Penetrating: creates abnormal passageways between the bowel and other structures like the skin • Inflammatory: inflammation without causing strictures or fistula Celiac Disease • an autoimmune disorder of the small intestine that occurs in genetically predisposed people. • Symptoms: chronic diarrhea, failure to thrive in children, fatigue. There are asymptomatic cases • Treatment: a gluten free diet Acid Reflux Acid is regurgitated and burns the esophagus Symptoms: Heartburn, Nausea, Chronic Salivation, Damage to esophagus Treatments are usually lifestyle (foods, positional therapy) changes along with medications and possibly surgery Acid Reflux • • • • Reflux esophagitis Esophageal strictures Barrett's esophagus Esophageal adenocarcinoma—a rare form of cancer. • http://www.youtube.com/watch?v=o4uln K5mK-A&feature=related