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108 Cards in this Set

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Mouth, pharynx, esophagus, stomach, samll intestion (duodenum, jejunum, ileum), and garge intestine (colon, rectum, anus).
What are the major structures fo the GI system?
Salivary glands, liver, gallbladder, and pancreas
List the accessory glandular organs.
Primary physiological function
is to provide nutrients for cell maintenance nad growth and to eliminate waste
What is the primary physiological function of the GI system?
Ingestion (taking in food), motility (mixing and propelling food through GI tract),
digestion (breaking down food),
absorption (movement of food particles in to bloodstream), elimination (waste eliminated from body).
What are the processes are required to provide nutrients and eliminate waste in the GI system
The primary physiological functions themselves.
By ANS and a variety of peptides, which are further classified as endocrines (Hormones), paracrines, and neurocrines.
How is the GI system regulated and coordinated?
All tissues
Endocrine release paracrines, which target specific tissues
What tissues are reached by the endocrines and what is released by the endocrines?
Can stimulate or inhibit the realease of endocrines and paracrines
What do neurocrines or neurotransmitters do?
Begins at the mouth and ends at the anus
Where does the GI system begin and end?
Opens into the pharynx (allows passage of nutrients and air).
What does the oral cabity open into and what does this allow for?
Connects to the esophagus and larynx
What does the posterior end of the esophagus connect to?
Pharynx to the stomach at the cardiac orifice.
What does the esophagus connect?
Deliver food to the stomach.
What is the main function of the stomach
Prevents aspiration and swallowing of excessive air
Upper esophageal sphincter prevents what?
Reflux of gastric contents into the esophagus
Lower esophageal sphincter (LES) prevents what?
Where is the stomach located?
In the upper abdomesn and below the diaphragm. Flask-shaped.
What is the purpose of the stomach?
Acts as a reservoir for chewed food, mixes ingested food with gastric secretions to form a semisolid liquid called CHYME, and regulates the release of chyme into the duodenum at a controlled rate.
What does the esophagus join?
Stomach at the cardia.
What does the cardia secrete?
Mucus that helps to protect the esophagus from the acidic secretions of the stomach
What are rugae?
Coarse folds that are located in the body and the fundus of the stomach.
What do gastric pits do and where are they located?
Contain the acid-secreting cells of the stomach and are located minly in the body of the stomach.
What is the antrum and what do they secrete?
Most dialtal area of the stomach and the site of G cells, which secrete gastrin.
Where is the pyloric sphincter located and what does it do?
Muscular structure between the stomach and the duodenum and minimizes intestinal reflux.
Where does most digestion and absorption take place?
Small intestine
How many sections is the colon traditionally divided into?
Six
What are the six sections and where are they located or connected to?
1. Cecum - most proximal section and is the location of the ileocecal valve
2. Vermiform appendix - protrudes posteriorly from the cecum.
3. Ascending colon - superiorly from teh cecum to the hepatic flexure.
4. Transverse colon - between the hepatic and splenic flexures.
5. Descending colon - extends from the splenic flexure to the level of the iliac crest.
6. Sigmoid colon - continues downward to the pelvic floor as the rectum.
What is the internal sphincter composed of
Smooth muscle.
What is the external sphincter composed of?
Skeletal muscle.
What is the colon responsible for?
reabsorption of electrolytes and fluid, thus allowing the body to maintain fluid and electrolyte balance with less fluid intake.
What are the layers of the GI system?
Mucosa - have villi which increase surface area in small intestine facilitating absoprtion, contain cells that are sensitive to chemical and mechanical stimuli.
Submucosa - contain peyers patches which are especially numerous in the ileum, secrete antibodies of IgA that protect the body.
Musularis propria - function in propulsion and mixing movements.
Serosa - outermost layer, forms part of the visceral peritoneum.
What is the extrinsic nervous system responsible for?
Parasympathetic - increases GI activity. Promotes motility, relax sphincters, and promote secretion
Sympathetic - inhibits activity.
What is the responsibility of the intrinsic nervous system?
Coordinates GI motility and secretion and helps coordinate function.
What enteric neuronal neurotransmitters are released?
Acetycholine, norepinephrine, serotonin, and dopamine.
What three branches of the abdominal aortic artery perfuse the GI organs?
Celiac axis - lower esophagus, stomach, duodenum, gallbladder, and liver.
Superior mesenteric artery - small intestine to transverse colon.
Inferior mesenteric artery - descending colon, sigmoid colon, and rectum.
Venous drainage of the stomach and small and large intestine are through what vein?
Through portal vein to the liver.
Does blood supply to the lower rectum and lower esophagus go through the portal vein?
No. Blood from the rectum drins into the inferior vena cava, through the rectal veins, which empty into the external iliac vein.
Blood from the esophagus drains through the hemiazygos and azygos veins into the inferior vena cava.
Where does the liver receive its blood supply?
Both venous and arterial sources. Venous - supplied from portal vein, which drains most of the blood from the GI tract. Arterial - by the common hepatic artery, which branches from teh celiac trunk, near the aorta and then perfuses the liver. Both drain into the hepatic vein, which in turn feeds into the inferior vena cava.
How much cardiac output does the GI system receive?
About 1/4 resting cardiac output. More than any other organ system.
Where is blood shunted when circulation is impaired?
Perfusion to the splanchnic bed is shunted to the systemic circulation. Splanchnic perfusion can be reduced without compromise but severe reduction can damage teh mucosal lining of the gut.
Name the three pairs of salivary glands.
Submaxillary, sublingual and parotid glands.
The salivary glands secrete what percentage of amylase that is used in digestion?
20%, the rest is secrested by the pancreas.
What causes saliva to be produced?
sight, smell, or thought of food, and by the pleasant or smooth texture of food in the mouth.
Which nerves send impulses to the salivary glands?
7th and 9th cranial nerves (Parasympathetic) and 1st and 2nd thoracic nerves (Sympathetic).
Parasympathetic stimulation or administration of what drugs mimic stimulation or enhance it?
Cholinergics stimulate. Neostigmine enhances it. Promote copious secretion of watery saliva.
Sympathetic stimulation produce what kind of secretions?
Scanty output of thick saliva. Cholinergic blockers (atropine) also inhibit salivation.
What does chewing do in the GI system?
Breaks down food into smaller particles which produces a bolus of food held together and lubricated by saliva that can then be propelled into the stomach by the process of swallowing.
What does mucus production do in the esophagus?
Protecs the esophageal lining from damage by gastric secretions or food and acts as a lubricant to facilitate the passage of food.
What is primary peristalsis?
Swallowing induced contractions of the esophagus.
What is secondary peristalsis?
Primary peristalsis is unable to clear the esophagus, food or fluid distends the esophagus. Distention stimulates stretch receptors that promote relaxation of the esophageal muscles ahead of the area of distention, and contraction of the esophageal muscles in and behind it.
What does hypertrophic LES do?
impedes esophageal emptying and can lead to overdistention of the lower esophagus.
What does an imcomptetent LES do?
results in repeated episodes of gastric reflux which can lead to lower esophageal strictures.
What are the major secretions of the stomach?
Hydrochloric acid, intrinsic factor, pepsinogen, gastrin, and mucus.
Why is intrinsic factor important?
Necessary for the absorption of Vitamin B12 in the small intestine.
What does hydrochloric acid do?
concerts pepsinogen to pepsin. Provides an ideal pH for the activity of pepsin. Breaks doen food molecules, and helps to protect the GI tract from bacterial invasion.
What is the role of mucus in the stomach?
lubricant and works with bicarbonate to neutralize acid, protecting the stomach wall from damage.
What can cause disruption of this barrier?
Bile salts, ETOH, ASA, NSAID's and H. Pylori.
What can inhibit secretion of hydrochloric acid?
Anything that blocks the histamine receptors such as H2 receptor antagonists or block the acetylcholine receptors like atropine. Proton pump inhibitors - inhibit H+/K+ adenosine triphosphatase (ATPase) enzyme pathway.
What factors stimulate gastric secretions?
ETOH, caffeine, and hypoglycemia.
What 3 phases regulate gastric secretions?
Cephalic, gastric, and intestinal phases.
What happens during the cephalic phase?
Sight, smell, taste, or thought of food stimulates brainstem centers. Mechanism by which emotions (fear, andger, depression - decrease secretions)can influence GI secretions.
What happens during the gastric phase?
Distention of the stomach by food stimulates stretch receptors. Eventually halted by stretch receptors and chemoreceptors in the wall of the stomach become refractory to stimulation, the acidity of the chyme inhibits further gastrin secretion, adn GIP decreased hydrochloric acid secretion adn gastric motility.
What happend during the intestinal phase?
Begins after chyme reaches the duodenum. Stretch receptors in the duodenum trigger peristalsis so that chyme is degraded, mixed with enzymes and diluents, and moved past the highly absorbent samll intestinal lumen.
What can cause delay in gastric emptying?
Vagotomy, presence of fats, proteins, or hydrochloric acid in the duodenal chyme, duodenal distention and intestinal hormones.
What causes vomit to be green?
When yellow bile from the duodenum is exposed to acid in the stomach.
What causes vomit to be brownish black (coffee-ground) color?
When blood is exposed to acid in the stomach. If rapidity of vomiting does not allow sufficient time for this interaction between acid and blood to occur, blood in the vomitus has it's normal red color (hematemesis).
What does endocrine tissue that is scattered throughout the pancreas responsible for?
Secrete insulin, glucagons, and panreatic polypeptide hormones, which aid in digestive process.
What neutralizes the highly acidid chyme from the stomach?
Bicarbonate
What do pancreatic enzymes digest?
Proteins - trypsin, chymotrispsin, elastase, and carbohypeptidase.
Fats - lipase, calipase, and esterase.
Phospholipase
Nucleic acids - nucleases
Starch - amylase
What is bile?
Mixture of bile salts, cholesterol, bilirubin,e and acids suspended in water.
What does bile do?
Ionizes fat-soluble vitamins into absorbable forms. Suspends choleterol, triglycerides, and mutliple-density percipitation and deposition of these molecules in the vasculature until they can be catabolized.
Where is bile stored and concentrated?
Gallbladder.
What activity stimulates the release of CCK
Digestion. CCK causes gallbladder contraction and relaxation of the sphincter of Oddi, allowing the release of bile into the duodenum to mix with chyme.
What do propulsive movements do in the small intestine?
Propel food forward, allowing for digestion and absoprtion. This peristalsis is stimulated by distention.
What do mixing movements do in the small intestine?
Localized concentric contractions fo the intestinal wall called segmentation promot mixing of food particles.
How does emptying of the small intestine happen?
Similar to that of gastric emptying. Peristaltic waves build up pressure in the ileum behind the ileocecal valve and push the chyme through the valve into the colon. The ileoceccal valve then prevents backflow. Ileal emptying can be retarded by intramural reflexes, which are initiated by a full (Distended) colon.
What are the major functions of the small intestine?
Absoprtion and digestion, which are facilitated by secretions from the pancreas, liver, and gallbladder.
What are the 3 major sources of carbohydrates in the human diet?
Sucrose, lactose, and starch. Converted to simple sugars.
Where does most digestion occur?
Duodenum and jejunum.
What fats are broken down in the small intestine?
Triglycerides, lipis, and phospholipids.
What do bile salts do?
In a process called emulsification, facilitate the creation of small droplets of fats from larger globules.
What happens if bile salts enter the colon?
They decrease the reabsorption of sodium and water, thereby increasing the liquidity of the undigested food residues in the colon.
What is the GI tract highly permeable to?
Water. Should a hypertonic solution enter the duodenum, osmosis occurs in the lumen. A hypotonic chyme in the stomach and duodenum causes an extremely rapid movement of water into the bloodstream.
What products can the human not digest?
Cellulose, hemicellulose, or lignin in plant tissues. These form a large portion of the undigested food residue.
What do these fibers (undigested food residue) do in the body?
attract and hold water, creating a larger, softer stool. Low quantities of bulk result in a relatively inactive colon, leading to bowel movements thar are relatively infrequent adn feces that are relatively small, dry, and difficult to pass.
What causes defacation to occur.
When the rectum fills this triggers defacation reflex by stimulating stretch receptors in the rectal wall. The urge to defacate occurs after the pressure within the rectum reaches 18 torr.
What happens to the urge to defacate during spinal shock?
In the early post-traumatic phase of spinal shock, the reflex does not work. After cord shock is ended, reflex defacation can occur once again, but voluntary inhibition is not possible (neurogenic bowel).
What can cause ammonia to remain in circulation instead of being absorbed?
People with seriously impaired liver function or with collateral circulatory routes that bypass the liver (usually the result of portal hypertentsion), such ammonia can remain in the circulation and lead to encephalopathy. Normally, ammonia is removed from the blood once it reaches the liver.
How are lobules?
Functional units of the liver.
What does the portal triad contain?
Two sets of afferent vessels (portal vein and hepatic artery) and a small bile duct.
How many lobules does the liver contain?
Between 50,000 and 100,000.
Where is the bile stored and concentrated when leaving the liver?
Gallbladder
What can increase the concentration of bile salts, cholesterol, and bilirubin 12-fold?
Fluid and electrolyte reabsorption in the gallbladder.
What is the maximum capacity of the gallbladder?
50 mL and can hold a 24-hour output of bile (600 mL) from the liver.
What happens when plasma glucose levels are high?
Hepatocytes remove glucose from plasma. Some of this glucose is then stored in teh liver as glycogen.
What happens when plasma glucose levels are low?
Hepatocytes convert the glycogen back into glucose through a process called glycogenolysis, and the glucose is released into the bloodstream.
Does the liver contain enough glycogen to buffer plasma?
The liver does not contain enough glycogen reserves to be able to buffer plasma glucose during prolonged fasting or severe exercise.
What happens when a hepatocyte is glycogen rich?
Conjugates bilirubin at a faster rate and is more resistant to toxins and infectious agents.
What happens to the amino acids from protein metabolism?
Deaminated to form ammonia by the liver, adn then converted to urea.
What does the liver synthesize?
Plasma proteins, including albumins, globulins, fibrinogens, plasma lipoproteins, adn other proteins involved in clotting.
What do albumins do?
Maintain normal plasma oncotic pressure.
What happens when the plasma oncotic pressure falls?
Leads to edema (pulmonary nad systemic) and contributes to ascites.
What do bile salts do?
Aid digestion by emulsifying dietary fats and fostering their absorption adn the absoprtion of fat-soluble vitamins through the intestinal mucosa. Also prevent the cholesterol in teh bile from precipitating out of solution and forming calculi.
What does bilirubin gluconate do?
Gives the bile it's normal golden yellow color. Organisms in the intesting convert most of the bilirubin gluconate into a darker brown compound, urobilinogen, which gives the feces it's natural brown color.
What happens when excess plasma levels of either conjugated (Direct)or unconjugated (Indirect)bilirubin happen?
Jaundice.
What happens when excess unconjugated bilirubin happens?
Can cross the blood-brain barrier and bind with the basal ganglia, resulting in kernicterus.
What is kernicterus?
Form of brain damage caused by excessive jaundice.
What happens when two MFO's (mixed-function oxidase) agents are administered withing a few hours of each other?
Causes each agent to act competitively, slowing down the degradation of the other. Outcome is higher blood levels of both chemicals for a longer time after administration. If administration of the second MFO drug is befun after MFO system induction, a larger dose of this drug will be required to produce a given effect.
What is MFO system induction?
Repeated administration of one MFO system-catabolized drug for several days causes the MFO system to enlarge physically and to possess more enzymes. Once induced, the MFO system degrades drugs more rapidly (including the drug that initiated teh induction).
What do liver cells degrade?
Steroid hormones, thereby preventing excess serum levels of estrogen, testosterone, progesterone, aldosterone, and glucocorticosteroids.