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25 Cards in this Set
- Front
- Back
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What are the 4 parts of the digestive system?
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1. upper part - mouth, esophagus, and stomach (acts as a receptable for food and where initial digestion takes place) 2. middle part - small intestine (where most digestive and absorptive process occur) 3. lower part - cecum, colon, and rectub (storage channel for waster eliminatio) 4. accessory organs - salivary glands, liver, and pancreas
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Describe how the musclular wall of the esophagus changes, proximal to distally
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- the upper third of the esophagus are skeletak-type striated muscle - these muscle fibers are gradually replaced by smooth muscle fibers - the lower third of the esophagus is entirely smooth muscle
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What is the cardiac orifice?
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the opening through which the esophagus opens into the stomach
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What portion of the small intestine digests and absorbs food?
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jejunum and ileum
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What are the 5 layers of the digestive tract?
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1. mucosal layer - produces mucus that lubricates and protects the inner surface 2. submucosal layer - connective tissue that contains blood vessels, nerves, and structures that secrete digestive enzymes 3. circular muscle layer 4. longitudinal muscle layer 5. outer serous layer - forms the peritoneum and is continuous with the mesentery
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What is the function of the mesentery?
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- a double-layered fold of peritoneum that suspends the jejunum and ileum - contains blood vessels nerves and lympatic vessels that supply the intestinal wall
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What are some characteristics of the greater omentum?
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- a filmy double fold of peritoneal membrane that extends from the stomach to cover the transverse colon and folds of the intestine - controls the spread of infection from GI contents by adhering to the inflamed area so that infection is less likely to enter the peritonenal cavity
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What are the 2 nervous systems that control GI function?
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1. Enteric nervous system - lies entirely within the wall of the GI tract; consists of the myenteric and submucosal plexus 2. autonomic nervous system - parasympathetic and sympathetic
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What is the function of the vagus nerve in the GI tract?
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- provides efferent parasympathetic innervation to the stomach,m small intestine, cecum, ascending colon, and transverse colon - increased vagal activity enhanced gastric motility
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What are some characterisitics of sympathetic innervation of the GI tract?
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- occurs through the thoracic chain of sympathetic ganglia - sympathetic stimulation inhibits gastric motility
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What are the 3 phases of swallowing?
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1. oral (or voluntary) phase 2. pharyngeal phase 3. esophageal phase
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Name 3 hormones produced by the GI tract
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1. gastrin - stimulates secretion of gastric acid and pepsinogen 2. secretin - stimulates secretion of bicarbonate-containing soution by pancreas and liver 3. cholecystokinin - stimulates contraction of the gall bladder; stimualtes secretion of pancreatic enzumes; slows gastric emptying
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What is the function of histamine in the GI tract?
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- histamine is released in response to gastrin and stimulates gastric acid secretion by the parietal cells
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What glands secrete saliva?
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parotid, submaxillary, sublingual, and buccal glands
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What are the 3 functions of saliva?
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1. protection and lubrication - protects the oral mucosa and coats the food 2. protective antibicrobial action - cleans the mouth and contains the enzyme lysozyme 3. initiate the digestion of dietary starches - contains ptayalin and amylase
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What are the 2 types of glands in the stomach mucosa?
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1. oxyntic (or gastric) glands - located in the proximal 80% of the stomach; secrete HCl, pepsinogen, intrinsic factor, and mucus 2. pyloric glands - located in the distal 20% of the stomach; secretes mainly mucus, some pepsinogen, and gastrin
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What is the function of intrinsic factor?
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necessary for the absorption of vitamin B12
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What are Brunner's glands?
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- mucus-producing glands located at the site where stomach contents enter the duodenum - produces alkaline mucus which protects the duodenum from the acid content in gastric chyme
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What is the difference between digestion and absorption?
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- digestion is the breakdown of foods into their constituent parts; requires hydrolysis, enzyme cleavage, and fat emulsification - absoprtion is the procces of moving nutrients and other materials from the external environment of the GI tract into the internal environment
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Describe how characteristic of the small intestine help in absorbtion
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- the small intestine has a large surface area due to circular folds and finger-like projections called villi - each villi has an artery and vein (which bring blood to the surface and receive nutrients) and a lymph vessel (or lacteal) that absorbs fat
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What are enterocytes?
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- the cells that cover each villus - contribute to the absorptive and difestive functions of the small bowel - secrete brush border enzymes that aid in the digestion of carbohydrates and proteins
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How are carbohydrates digested and absorbed?
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- first they are broken down into monosaccride by various enzymes (ie. lactase, sucrase, amylase, maltase, alpha-dextrimase) - some carhbohydrates are absorbed by facilitated diffusion (fructose) - others require ATP (glucose and galactose)
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Describe how fats are absorbed
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- fats (or triglycerides) are broken down by gastric and pancreatic lipase - Bile salts carry the fatty acids and fat soluble vitamins to the intestinal villi, by forming micelles, where they are absorbed
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What is steatorrhea?
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- fatty stool - occurs when fat is not absorbed in the intestine and is excreted in the stool
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What enzymes breakdown proteins?
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- pepsin (precursor is pepsinogen) begins digestion in the stomach - trypsin (precursor trypsinohen), and chymotrypsin, carboxypeptidase, andelastase continues digestion in the duodenum
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