FINAL GI Flashcards
Describe how layers of the GI tract are innervated. What is the name of the plexus that is dispersed throughout the walls of the GI tract?
A network of intrinsic nerves that controls mobility, secretion, sensation, and
blood flow is located solely within the GI tract and controlled by local and autonomic nervous system
stimuli through the enteric (aka INTRAMURAL) PLEXUS located in different layers of the GI walls
(see figure 35.2 in first edition text for a good image of this!)
Is salivation controlled by sympathetic or parasympathetic system?
Both.
Cholinergic parasympathetic fibres stimulate the salivary glands, and atropine (an anticholinergic agent)
inhibits salivation and makes the mouth dry. β-Adrenergic stimulation from sympathetic fibres also
increases salivary secretion.
Describe the esophagus in terms of portions that are voluntary and involuntarily controlled. How is each section innervated?
The pharynx and upper third of the esophagus contain striated muscle (voluntary) that is
directly innervated by skeletal motor neurons that control swallowing.
The lower two-thirds contain
smooth muscle (involuntary) that is innervated by preganglionic cholinergic fibres from the vagus nerve.
How is peristalsis stimulated in the esophagus?
Peristalsis is stimulated when afferent fibres distributed along the length of the esophagus sense
changes in wall tension caused by stretching as food passes.
The esophagus has both intrinsic and extrinsic innervation. Describe what this means
Extrinsic innervation = innervated by the vagus nerve
Intrinsic = also innervated by enteric nervous system, which is inside the walls of the esophagus. This is the same as the enteric/intramural plexus
**The enteric plexus serves as a type of secondary wave of peristalsis if the initial wave doesn’t get the food all the way to the stomach
When the swallowing reflex is initiated, afferent sensory information is sent to the swallowing center via 3 cranial nerves. Which 3 are they?
Efferent (motor) info is then sent back via 2 nerves…which are they?
Sensory:
Glossopharyngeal
Vagus
Trigeminal
Motor:
Vagus & glossopharangeal
What nerve is the primary control for tone of the lower esophageal sphincter?
Vagus! (basically, vagus for everything)
What are the two plexuses that constitute the enteric (intramural)
nervous system? (this is likely too detailed, but it does say that basically all of the GI tract has this intrinsic innervation)
myenteric plexus (Auerbach
plexus) and the submucosal plexus (Meissner plexus)
Sympathetic vs parasympathetic innervation of the stomach - what is responsible for each?
What nervous system
The vagus nerve provides parasympathetic innervation, and
branches of the celiac plexus innervate the stomach sympathetically.
the enteric (intramural)
nervous system within the stomach responds to local stimuli.
What is the function of bile?
Aids in intestinal digestion of fats. Bile salts aid in fat emulsification and absorption. Fats are broken down into fatty acids that are absorbed across the intestinal mucosa as micelles (water soluble fat products).
What is bile?
Yellow green alkaline fluid containing bile salts, cholesterol, bilirubin, electrolytes, and water. It is important in intestinal fat digestion and absorption.
Describe the production and flow of bile.
Bile is produced by the hepatocytes and moves through the liver via bile canaliculi to drain into bile ducts that eventually drain into the common bile duct. This leads to the ampulla of vater (where the bile duct and pancreatic duct meet), which empties into the duodenum called the major duodenal papilla (surrounded by the sphincter of oddi). If the spincter is closed (i.e., in periods between meals), bile backs up and is stored in the gall bladder.
What blood vessel returns bile salts absorbed in the terminal ileum to the liver?
Portal vein (enterohepatic circulation)
What stimulates the gallbladder to contract?
Food in the duodenum about 30min after eating. Contraction stimulated by the vagus nerve.
What stimulates the gallbladder to relax?
Sympathetic stimulation, vasoactive intestinal peptide, pancreatic polypeptide.
What is the function of the gallbladder?
Sac like organ on the inferior surface of the liver that stores and concentrates bile between meals. The mucosa of the gall bladder wall readily absorbs water and electrolytes, leaving a high concentration of bile salts, pigments, and cholesterol.
Define cholelithiasis
Formation of gallstones
Describe the epidemiology of cholelithiasis
More prevalent in developed countries and Indigenous populations
More common in women than men
Risk factors include obesity, middle age, pregnancy, use of oral contraception, rapid weight loss, genetic predisposition, and gallbladder, pancreatic, or ileal disease
True or false: gall stones are always symptomatic
False- can be asymptomatic for months to years. Symptoms result if gallstones become lodged in the cystic or common duct during contraction of the gallbladder.
What is the most common type of gallstone?
Cholesterol
What do all gallstones contain?
Cholesterol, unconjugated bilirubin, bilirubin calcium salts, fatty acids, calcium carbonate and phospates, and mucin glycoproteins
True or false: many gallstones can fill the entire gallbladder
True
When do gallstones become symptomatic?
When they become lodged in the cystic duct (or any part of bilirary tract), obstructing flow of bile out of the gallbladder, causing pain and inflammation
What are the two types of inflammatory bowel disease?
Crohn’s Disease and Ulcerative Colitis
Outline the epidemiology of IBD.
Age of onset 10 – 40 (CD 10-30; UC 10-40)
Equal prevalence between men and women
Higher prevalence in Caucasians, Ashkenazi Jewish populations
Family history/genetic susceptibility
DIFFERENCE: smoking/nicotine increases risk of CD but reduces risk of UC
True or false, IBD is an autoimmune disease?
True
What kind of pain is characteristic of gallstones
Epigastric, right hypochondrium (RUQ), intolerance to fatty foods are cardinal manifestations
Pain occurs 30 min to hours after eating a fatty meal, and may be constant or intermittent.
May also have vague symptoms like heartburn, flatulence, epigastric pain, discomfort
Where does the inflammation occur in the two types of inflammatory bowel disease?
In Crohn’s Disease – begins in intestinal submucosa and spreads discontinuously. Small bowel involved, right sided colonic involvement, rectum usually not involved. Bowel wall affected asymmetrically and segmentally with skip areas, patchy inflammation with ulcerations extending transmurally (throughout the layers of organ wall)
Ulcerative Colitis – lesion begins with the base of the crypt of Lieberkuhn in large intestine. Starts with the rectum and may extend to entire colon. Bowel wall affected symmetrically with uninterrupted pattern, inflammation is uniform and diffuse, affects mucosal layer
What is the time course of IBD?
Age of onset 10 – 40 (CD 10-30; UC 10-40)
Chronic disease with remissions and exacerbations
Incurable
Jaundice indicates a gallstone is lodged in the _______________duct
common bile
Describe the signs and symptoms in Crohn’s disease
Lesions from mouth to anus (terminal ileum and colon most common)
Lesions discontinuous
Entire intestinal wall inflamed
Transmural granulomata are common – cobblestone appearance
Ulcerations are deep fissures, fistula common
Narrow lumen and obstruction common
Small intestine malabsorption common
Abdo pain – classically RLQ, moderate-severe
Diarrhea/constipation/vomiting
+ many extraintestinal symptoms
Describe the signs and symptoms of ulcerative colitis
Continuous lesions in the large intestine
Mucosal layer inflammation
Ulcerations superficial crypt abscesses
Abdo pain – mild-severe
Diarrhea common, frequent small volume, mucous, severe urgency (tenesmus)
Bloody stool common
+ many extraintestinal symptoms
What is the laboratory stool test which can differentiate IBS from IBD?
Fecal calprotectin – indicates migration of neutrophils to intestinal wall.
What other diagnostic testing would be beneficial with IBD?
Labs related to inflammation, nutritional status and anemia
Stool studies to rule out other causes such as cdiff, parasites
Imaging: abdo xray (bowel wall thickening, obstruction, toxic megacolon, perforated bowel); Barium enema (colon xray, shows mucosal patterns differentiating CD from UC). US, CT and MRI more limited use.
Gold standard for diagnosis: Colonoscopy
May also require flexible sigmoidoscopy
What are some pharmacological management options with IBD?
5-aminosalicylate (higher efficacy in UC)
Corticosteroids
Immunosuppressants
Monoclonal antibodies/Anti- tumor necrosis factor (TNF) therapies
Antibiotics for infections
Symptomatic treatment with analgesics, antidiarrheals, iron supplements, anticholinergics for cramps
What are some non-pharmacological management options with IBD?
Fecal transplant
Probiotics
Diet changes
Describe the treatment of gallstones
Oral bile acids may dissolve stones
Dietary modifications may prevent development of gallstones (reducing intake of poly and mono unsaturated fat and caffeine; increasing fibre intake)
Endoscopic removal of gallstones
Lithotripsy of large stones
What role does surgery often play in crohns/UC?
Surgery is not curative, indicated for failed medical therapy, recurrent disease, fistula, abdominal abscess, stricture, malignancy, acute obstruction, peritonitis, perforation, toxic megacolon, major hemorrhage.
Goal to remove grossly involved bowel and spare as much normal bowel as possible
Crohn’s - 80% require surgery at some point in disease
UC – 20% require surgery at some point in disease
Define cholecystitis
Inflammation of gallbladder or cystic duct
Describe epidemiology of cholecystitis
Affects 16-18% of Canadians. Predisposing factors include increasing age (above 40), obesity, gallstone disease, female, prolonged fasting, use of cholesterol lowering drugs, bile acid malabsorption
Describe the pathophysiology of cholecystitis.
Acute or chronic inflammation of the gall bladder wall.
Acute caused by gallstones lodged in cystic duct- causes the gallbladder to become distended and inflammed. Pressure against the distended gallbladdder wall decreases blood flow and may result in ischemia, necrosis, and perforation.
What are signs and symptoms of ACUTE cholecystitis
Abrubt, severe, constant RUQ epigastric pain that may radiate to back or shoulder. Similar pain to gallstones that is worse following 30 min ingestion of fats. Fever, leukocytosis, rebound tenderness, abdo guarding, nausea, and vomitting may occur in severe cases.
What are signs and symptoms of chronic cholecystitis
Vague symptoms or biliary colic prior to cholecystitis; exaccerbation and remission pattern
Describe diagnosis of cholecytisits
Positive Murphys signs (tenderness to R subcostal area with palpation during deep inspiration- don’t press hard or you may rupture the gallbladder!)
CBC- leukocytosis, elevated CRP, poss elevated liver enzymes and bilirubin
CT or gallbladder US to confirm diagnosis.
*Differentiate from pancreatitis, MI, pyelonephritis
Describe management of acute cholecystitis
Symptom management/ pain control/ antiemetics
Antibiotics for infection in severe cases
May require cholecystectomy
*chronic attacks treated with low fat diets and potential cholecystectomy in the future
Irritable bowel syndrome is a disorder of the ______ - _______ axis
The brain-gut axis