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BIO161 - Digestive
BIO161 - Digestive System
Question | Answer |
---|---|
What does the alimentary canal consist of? (in order) | mouth, esophagus, stomach, small intestine, large intestine |
What are the components of the small intestine? How large is the small intestine? | duodenum, jejunum, ileum;about 20 feet long |
What are the components of the large intestine? | cecum (with the appendix attached), ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus |
Where are the flexures in the large intestine located? What are they called? | the hepatic flexure is located between the ascending colon and the transverse colon; the splenic flexure is located between the transverse and descending colon |
What are the accessory digestive organs? (6) | salivary glands (parotid, submandibular, sublingual), teeth, tongue, liver, gallbladder, and pancreas |
What are the 2 types of digestion? | mechanical & chemical |
What is mechanical digestion? | the physical breakdown of food into small particles, thereby increasing the surface area for enzyme action |
What is an enzyme? | a catalyst; speeds up a reaction (not used up in the process) |
What is chemical digestion? | breakdown of food into basic building blocks by enzymes; the building blocks are absorbed in the small intestines |
What are the 3 main food groups? What are the other 3 food groups? | the main food groups are carbohydrates, proteins, and fats; the other food groups are vitamins, minerals, and water |
What is ingestion? | taking in of food into the mouth |
What are the 3 types of carbohydrates? | complex (polysaccharides), disaccharides, and monosaccharides |
What is a complex carbohydrate? | consists of many glucose units joined together; these are starches; examples are amylose and amylopectin |
What is a disaccharide? | 2 monosaccharides joined together |
What are the 3 main disaccharides? | sucrose (common table sugar): 1 molecule glucose + 1 molecule fructose; maltose: 2 molecules of glucose; lactose (milk sugar): 1 molecule of glucose + 1 molecule of galactose |
What are monosaccharides? | made up of a single glucose unit: examples: glucose, galactose, gructose |
What are all carbohydrates ultimately absorbed as? | glucose |
What is the ultimate body fuel? | glucose |
What are the building blocks of protein? How are the building blocks joined together? | amino acids are protein's building blocks; they join together with peptide (covalent) bonds to form peptides |
How many naturally occuring amino acids exist? | 22 |
What is the threshold for when a string of peptides is considered a protein? | >= 50 linked peptides make a protein; < 50 is a chain of peptides (i.e. dipeptide, tripeptide, etc) |
How are proteins absorbed by the body? | as amino acids |
What do fats consist of? | trigylcerides: glycerol & fatty acids |
What is the composition of saturated and unsaturated fats? | saturated fats are lard or fat (unhealthy); unsaturated fats form double bonds and are typically oils |
What is the result when carbohydrates, proteins, and fats are digested? | glucose (carbs), amino acids (proteins), and fatty acids and glycerol (fats) |
After ingestion, what is the next digestive process? | mastication; chewing of food by the teeth and the tongue mixing it with saliva to form a bolus |
What are the components of the teeth (from outer to inner) | enamel, dentin, pulp cavity |
Which layer has blood vessels & nerves? | the pulp cavity |
What are the different types of teeth? What are the dental formulas for permanent and deciduous teeth? | incisors - i (front teeth); canine - c (bites food); premolar - p; molar - m; permanent teeth: 2i, 1c, 2p, 3m; deciduous teeth: 2i, 1c, 2p, 0m |
What are the tongue muscles used for? What nerve controls them? | the tongue has intrinsic muscles innervated by the hypoglossal nerve; they are involved in speech, swallowing, and taste |
What part of the tongue is responsible for taste? Which nerves are involved? | the taste buds are called the papillae; they are located on the surface of the tongue; taste is handled by the facial & glossopharyngeal nerves |
What are the 5 taste sensations? | sweet, sour, bitter, salt, umami |
What are the different types of papillae? | fungiform, filliform, vallate (or circumvallate) |
What do each of the salivary glands produce? | parotid - mucous & salivary amylase; sublingual - mostly water & mucous; submandibular - mucous |
What happens to the bolus once it is formed by the tongue? | it is delivered to the oropharynx where the involuntary phase of swallowing is initiated; the bolus is then passed to the upper part of the esophagus and moves down this tube by peristalis |
What are the layers of the GI tract (from inside to outside)? | mucosa, submucosa, muscularis externa (consists of the longitudinal & circular muscles), and the serosa (aka adventitia) |
What is peristalsis? | alternating contraction & relaxation waves created by the muscles of the GI tract; pushes the bolus down to the stomach |
What are the 2 sphincters in the stomach called, and where are they located? | the gastroesophageal sphincter (aka cardia sphincter) is located where the esophagus meets the stomach; the pyloric sphincter is located at the bottom of the stomach where it joins to the small intestine |
What is a sphincter and what is its function? | it is a muscular structure that prevents backflow (like a valve) |
What is the function of the stomach? | storage site for partially digested food |
What are the regions of the stomach? Where is the stomach located? | cardia (around the GE sphincter), fundus (top rounded portion), body, antrum, and pyloris; the stomach is located in the epigastric area |
Where does the stomach join the small intestine? | the pylorus region of the stomach joins the small intestine at the pyloric sphincter |
What is the 3rd muscular layer in the stomach called? What are the other 2 muscular layers called (i.e. found in the entire GI tract)? | the 3rd layer is the oblique layer which mixes or churns the food into chyme; the other 2 muscular layers are the longitudinal and the circular layers |
Where is the greater curvature found? What is attached to it? | the greater curvature is on the left side of the stomach; the greater omentum attaches here |
Where is the lesser curvature found? What is attached to it? | the lesser curvature is the "inside" curve of the stomach, on the right side; the lesser omentum is attached here |
What is the pH of the stomach? | between 1.5 - 3.5; very acidic |
What is in gastric juice? | hydrocloric acid, enzymes (especially pepsin), intrinsic factor, and gastric lipase (per review sheet) |
Where does protein digestion begin? Carbohydrate digestion? Which enzymes are involved? | protein digestion begins in the stomach (pepsin breaks down the proteins to peptides); digestion of carboyhdrates begins in the mouth (amylase starts the process) |
How is the small intestine modified for absorption of nutrients? | the mucosal layer of the jejunum and the ileum is modified into finger-like structures called villi; this increase the surface area of the intestines |
What is the exocrine function of the pancreas? | it secretes pancreatic juice into the duodenum via the pancreatic duct |
Which ducts empty into the duodenum? | the hepatopancreatic duct empties into the duodenum via the sphincter Oddi; the hepatopancreatic duct is formed from the joining of the pancreatic & common bile ducts |
What is the purpose of bile? Where is it produced? Where is it stored? | bile emulsifies (breaks down) fats; it is produced by the liver and stored in the gallbladder |
What is the common bile duct? | the liver releases bile into the hepatic duct; the gall bladder utilizes the cystic duct; the joining of the hepatic duct and the cystic duct creates the common bile duct |
What does pancreatic juice contain? | bicarbonate (pH of 8 to neutralize the acidic contents from the stomach) and enzymes (pancreatic lipase, pancreatic proteases, pancreatic amylase) |
What is the function of lipases? | ensymes that break down fats into glycerol & fatty acids |
What is the function of proteases? Which proteases are contained in pancreatic juice? | proteases digest protein; the pancreatic proteases are chymotrypsin, trypsin, and carboxypeptide |
What is the function of amylase? | carbohydrate digestion |
What is the main function of the small intestine? What component of the small intestine handles that? | the small intestine is mainly involved in absorption of food through the villi |
Where are glucose & amino acids absorbed? fatty acids? | all are absorbed by the villi of the small intestine; glucose & amino acids are absorbed through the blood capillaries; fatty acids are absorbed thru the lacteals to the cysterna chyli (then to thoracic duct, hepatic portal vein, liver) |
Which vitamins are fat-soluble? Where are they absorbed? | A, D, E, and K are fat soluble; they are absorbed during the digestion of fats |
Which 3 structures of the small intestine are adapted for absorption? How? | the villi, plica circularis, and microvill are all adapted for absorption because they increase the surface area of the small intestine |
What are the brush borders of the microvilli? | They are the last set of digestive enzymes: lactase, sucrase, peptidases, and intestinal lipase |
What is the main function of the large intestine? | absorption of water |
How is vitamin K synthesized? What is the function of Vitamin K? | from the bacteria in the colon; vitamin K stops bleeding |
What is the purpose of the sigmoid colon? | it pushes its contents as feces to the rectum, where it is store |
What are the 2 anal sphincters? | the internal anal sphincter is controlled involuntarily; the external anal sphincter is controlled voluntarily |
Where are carbohydrates digested? What enzymes are involved? | starts in the mouth (salivary amylase); no digestion occurs in the stomach; pancreas (pancreatic amylase); in the small intestine disaccharides are converted to monosaccharides (intestinal amylase) |
Where are proteins digested? into what forms? what enzymes? | no digestion in the mouth; stomach: pepsin breaks protein into peptides; pancreas: trypsin, chymotrypsin, and carboxypeptidase continue breaking down the peptides into smaller peptides; small intestine: peptidases break the peptides into amino acids |
Where are fats digested? which enzymes are involved? | mouth: no digestion; stomach: gastric lipase breaks down fats into fatty acids and glycerol; pancreas: pancreatic lipase continues the breakdown; small intestine: intestinal lipase completes the process |
What is intrinsic factor? | required for absorption of vitamin B12 |