The Digestive System Lab Organs of the Digestive
The Digestive System Lab
Organs of the Digestive System § Gastrointestinal tract (GIT) – continuous passageway which contains the food from the time it enters the body until it leaves; organs include: § mouth (oral cavity), pharynx (oropharynx & laryngopharynx), esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), anal canal, anus § Accessory organs - participate in digestive processes; organs include: § teeth, tongue, salivary glands, liver, gall bladder, pancreas
Function of the Digestive System § To break down food into a “usable” (absorbable) form – occurs through mechanical processing & chemical digestion § To supply our cells with the nutrients they need for energy, growth & repair
Classes of Nutrients: § carbohydrates – including § polysaccharides (“complex” carbohydrates ) § starch § disaccharides (“simple” sugars) § maltose, sucrose, lactose § proteins § fats (lipids/triglycerides) § vitamins § minerals § water No digestive processes necessary, just absorption
Digestive processes § Mechanical processing – physical breakdown of food; e. g. mastication, emulsification, mixing waves, segmentation § Chemical digestion – chemical breakdown of food; disassembling of organic molecules into their component parts; requires enzymes § carbohydrates (polysaccharides) disaccharides monosaccharides § proteins amino acids § lipids (triglycerides) fatty acids & glycerol (monoglycerides)
Mouth (oral cavity) Digestion (mechanical & chemical) begins within the oral cavity – § mastication § production of saliva by salivary glands Parotid gland Sublingual gland Submandibular gland saliva – made of H 2 O, salts & salivary amylase; moistens foods to create “bolus” to help with deglutition, & begins chemical digestion of starch Starch (polysaccharide) amylase Maltose (disaccharide)
Stomach Mechanical digestion – mixing waves to change bolus of food to “chyme” Chemical digestion - secretions from cells of stomach to begin protein digestion: Peptic (chief) cells – pepsinogen Parietal cells – hydrochloric acid (HCL) Pepsinogen + HCL Pepsin Proteins Pepsin HCL polypeptides
Small intestine Chyme from stomach (with partially digested starch & proteins) + Bile from liver & gall bladder + Pancreatic juice from pancreas – released into duodenum of small intestine Segmentation mixes chyme with other secretions Fats + bile emulsified fats bile
Pancreas Pancreatic juice – mixture of enzymes & buffers (sodium bicarbonate) secreted by acinar cells into pancreatic duct & released into duodenum § pancreatic amylase Starch maltose § lipase Lipids (triglycerides) fatty acids + monoglycerol § proteases (trypsin, chymotrypsin, carboxypeptidase) Proteins & polypeptides dipeptides) small peptides (tripeptides & § nucleases – digest RNA & DNA Stomach § sodium bicarbonate – neutralizes acidic chyme because enzymes in small intestine need an alkaline p. H Tail Body Head
Small intestine Cells in jejunum and ileum produce peptidases and disaccharidases for final digestion of proteins and sugars small polypeptides, tripeptides, dipeptides maltose sucrose lactose maltase sucrase lactase peptidases amino acids glucose + fructose glucose + galactose
Absorption of monosaccharides (glucose, fructose, galactose), amino acids and fatty acids (as well as vitamins/minerals) occurs in small intestine (into blood or lymph (fatty acids) Absorption of water (and some vitamins) occurs in large intestine
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