4C A&P and Pathology of the Large Intestine Flashcards
Which intestine is longer, small intestine or large intestine?
Small intestine is longer, however, the large intestine has a larger diameter though it is only about 5 feet long
Which intestine has a larger diameter?
Large intestine
What are the fibers of the external muscular layer of the large intestine collected into?
Longitudinal bands called teniae coli
Why are outpouchings called haustra formed between the teniae coli?
B/c teniae bands are shorter than the rest of the colon
Are there any villi in the mucosa of the large intestine?
No!
What are the general parts of the large intestine?
Cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, and rectum
What do the crypts of the large intestine contain?
Absorptive cells, goblet cells, endocrine cells, and regenarative cells
How do the large intestine cells compare to the small intestine cells?
Large intestine cells have scant microvilli
What do the absorptive cells of the large intestine absorb?
Mainly water, and may absorb some vitamins that are made by bacteria
What do goblet cells do in the large intestine?
Secrete mucus to make it easier for stools to pass
What type of endocrine hormones are secreted in the large intestine?
Paracrine hormones
What are the four major functions of the large intestine?
Propulsion and storage of unabsorbed material
Place of residence for flora
Absorption of small amounts of water and electrolytes
Defecation
Do we have any normal bacteria in the large intestine? Small intestine?
Large intestine has a complex family of bacteria about 500 species.
Small intestine has some bacteria but not nearly as much as the large intestine
Does the colon have bacteria at birth?
No, it is sterile. But the intestinal bacteria flora becomes established early in life
What are some of the established roles of intestinal flora?
Fermentation of undigestable dietary fiber to generate FAs, which are a major nutritional source for the colon and have trophic effects that promote normal mucosal growth and development.
Creation of inhospitable environment to pathogenic organisms
Metabolism of various compounds - bile salts and certain drugs.
Creation of vitamin K, B12, and Folic Acid
What is responsible for the slightly acidic nature of stools (pH 5.0 to 7.0)?
The organic acids made by the colon bacteria
What leads to gas formation in the large intestine?
Fermentation of indigestible sugars
What are the four distinct mechanisms of diarrhea?
Increased osmotic load.
Increased secretion of fluid into the LI
Inflammation of LI lining
Decreased absorption time (very very fast motility) - too fast for water to be absorbed in the colon
When does osmotic diarrhea occur?
When you have something in the gut that is not absorbable and it attracts a lot of water. E.g, lactose intolerance, poorly absorbed salts, or large ingestion of hexitols (sorbitol)
When does secretory diarrhea occur?
When the small and large bowel secrete more electrolytes and water than they absorb. Caused by bacterial toxins such as from cholera, enteropathetic viruses, bile salts and unabsorbed dietary fat
What causes exudative diarrhea?
Several mucosal diseases that cause mucosal inflammation, ulceration, or tumefaction - resultant outpouring of plasma, serum proteins, blood, and mucus increases fecal bulk and fluid content
When does diarrhea due to decreased absorption time occur?
When chyme is not in contact with an adequate absorptive surface of the GI tract for a long enough time so that too much water remains in the feces
What are some factors that decrease contact time?
Small or large-bowel resection, gastric resection, vagotomy, surgical bypass of intestinal segments, and drugs that speed transit by stimulating intestinal smooth muscle (as a side effect)
What is constipation?
Infrequent passage of stool
When does constipation increase in a person’s life?
With age, especially after age 65
What drugs tend to cause constipation?
Opiates, anti-cholinergics, calcium channel blockers, diuretics, iron supplements, and aluminum antacids
What is irritable bowel syndrom (IBS)?
A functional GI disorder characterized by a variable combination of chronic and recurrent intestinal symptoms not explained by structural or biochemical abnormalities
Evidence suggest that what percentage of people in the Western countries have IBS?
10-20%, but most don’t seek medical attention
What is IBS believed to be a result of?
Dysregulation of intestinal motor and sensory functions modulated by the CNS. Tends to be increased by psychological and physiologic stress
What is associated with the onset of IBS?
Menarche (first menstrual cycle, female puberty), women experience exacerbation of symptoms during the pre-menstrual period - suggesting a hormonal component
What is inflammatory bowel disease (IBD)?
Two related inflammatory intestinal disorders - Crohn disease and ulcerative colitis
Is Crohn disease and ulcerative colitis distinguishable?
Yes, but they have many features in common
What do Crohn disease and ulcerative colitis have in common?
Inflammation of the bowel, both lack confirming evidence of a proven causative agent, and both can be accompanied by systemic manifestations
What are Crohn disease and ulcerative colitis ultimately the result of?
Activation of inflammatory cells with elaboration of inflammatory mediators that cause non-specific tissue damage
What are Crohn disease and ulcerative colitis characterized by?
Remissions and exacerbations of diarrhea, fecal urgency, and weight loss. Acute complications such as intestinal obstruction may develop during periods of fulminant disease.
With IBD, which regions of the gut are affected for Crohn disease and for ulcerative colitis?
Crohn disease - the ileum and/or colon are affected. In ulcerative colitis ONLY the colon is affected.
How does the tissue lining in Crohn disease differ from ulcerative colitis?
Crohn has a cobble-stone appearance - and thickening. Ulcerative colitis has lots of ulcers, bleeding - and thinning of the intestinal wall.
What does any drug that ends in -mab mean? eg - adalimumab
Monoclonal antibody (from an animal)
What is the manifestation of Crohn disease in the oral cavity?
Cobble-stone appearance of buccal mucosa. Diffuse labial, gingival or mucosal swelling. May preceded intestinal involvement. Occurs in 8-29% of pts
What is Diverticulosis?
When the mucosal layer of the colon herniates thru the muscularis layer
What is Diverticulosis characterized by?
Presence of diverticula in the colon (usually sigmoid colon) and generally asymptomatic
What is the cause of Diverticulosis?
High intraluminal pressure on areas of weakness in the bowel wall
What is Diverticulitis?
When diverticula become inflammed, no longer just Diverticulosis (which is usually asymptomatic)
What are the most common complaints of Diverticulitis?
Pain in LLQ, nausea, vomiting, tenderness in LLQ, slight fever, elevated WBC count
What are complications of Diverticulitis?
Perforation with peritonitis, hemorrhage, and bowel obstruction
What is acute appendicitis?
Inflammation of the veriform appendix due to an obstruction with stool or a twisting of the organ or its blood supply
Where is the pain in acute appendicitis?
LRQ
Where does the appendix dangle from?
The cecum.
What can occur if swollen appendix bursts before surgery?
Peritonitis. Treatment w/ antibiotics becomes necessary
What are the major mechanical causes of mechanical obstruction?
Herniation of a segment in umbilical or inguinal regions.
Adhesion b/w loops of intestine
Volvulus (twisting of intestine)
Intussusception (piece of intestine that folds back on itself - like a hose within a hose)
What kind of reflex is the defecation reflex?
Spinal-cor mediated parasympathetic reflex - causes the walls of the sigmoid colon and the rectum to contract and the internal anal sphincter to relax
What is the defecation reflex initiated by?
Pressure in the sigmoid colon and the rectum
What is the Valsalva maneuver?
Voluntary aiding of defecation by closing the glottis and contracting our diaphragm and abdominal muscles
What is hematemesis?
Blood in the vomitus
What does bright red blood in stools indicate?
Bleeding is from the lower bowel. When it coats the stool it is often the result of bleeding hemorrhoids
What is melena?
Passage of black or tarry stools
What do tarry stools indicate?
Source of bleeding is above the level of the ileocecal valve, although this is not always the case
How can occult bleeding be detected?
Only way is by chemical means. Can be caused by gastritis, peptic ulcer, or lesions of the intestine
How common is adenocarcinoma of the colon and rectum?
One of the most common cancers in the Western World
When does adenocarcinoma of the colon and rectum peak?
60-70 years of age
How does adenocarcinoma of the colon and rectum begin?
Formation of polyps (looks like a single cobble stone) - a tissue that is dangling somewhere from the colon wall. Could be metastatic
What are predisposing factors for adenocarcinoma of the colon and rectum?
Polyps, long-standing UC, genetic factors, and low fiber, high animal fat diet
