4 C: Anatomy, Physiology and Path of the Large Intestine (Colon) Flashcards
The diameter of the colon is _________ than that of the small intestine
GREATER
What is teniae coli?
The fibers of its external muscular layer are collected into longitudinal bands
What are Haustra?
Because these bands are shorter than the rest of the colon, the colon wall forms OUTPOUCHINGS between the teniae.
Are there vilii on the mucosa?
In the large intestine?
NO
What do the general parts of the colon include?
The cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, & rectum.
What are crypts of Lieberkuhn?
Glands composed of simple columnar type of epithelium
What are the 4 cells that constitute this epithelium?
1) Mucus-producing goblet cells
2) Absorption cells that fxn in absorbing nutrients, electrolytes, and fluid
3) Regenerative cells that proliferate and replace the other cells of the epithelium
4) Enteroendocrine cells that release paracrine hormones
What is the outer longitudinal layer is called what?
The Muscularis Externa
Note: it is gathered into the teniae coli
What is frequently noted in BOTH the small and large intestine?
Lymphatic nodules and lymphoid infiltration
What are the function of the large intestine?
1) propulsion & storage of unabsorbed material
2 ) place of residence for flora (bacteria)
3) absorption of small amounts of water and electrolytes
4) defecation
The large intestine is home to what?
A complex family of bacteria (500 diff species of bacteria reside in the colon)
What role do the bacterial species play?
In the maintenance of health and prevention disease
Where are large masses of bacteria passed in?
Stool
When do the intestinal bacterial flora become established?
At birth, the colon is sterile, but the intestinal bacteria flora becomes established EARLY in life
What are some of the established roles of intestinal flora?
Fermentation of undigestible dietary fiver to generate fatty acids, which are major nutritional source for the colon and have trophic effects to promote normal mucosal growth and development.
What is responsible for the slightly acidic nature of stools?
What is the pH?
The organic acids
pH= 5.0- 7.0
What leads to gas formation?
Fermentation of indigestible sugars
What prevents the colonization of the GI tract?
Creation of an environment that is inhospitable to pathogenic microorganisms
What is the mechanism is believed to be apart of the colonization of bacteria?
Not completely understood, but the fact that if there is a million good then it is hard for bad bacteria to take over.
***Another factor is pH
Why is pH a factor?
Many of the normal flora have a low pH optimum, where many pathogens favor a neutral or more alkaline environment
Intestinal flora is also involved in what 3 things?
1) Creation of an environment that is inhospitable to pathogenic microorganisms
2) Metabolism of various compounds including bile salts, certain drugs
3) Creation of vitamin K, vitamin B12 & folic acid
What is vitamin K essential to?
The liver for the efficient synthesis of certain blood clotting factors (e.g., prothrombin, VII, IX, & X)
What is vitamin B 12 and folic acid essential for?
Important for final maturation of erythrocytes
What are some cause of Diarrhea?
Infectious, drug-induced, food-related, post-surgical, inflammatory, transit-realted, and psychologic
What are the 4 distinct mechanisms that produce diarrhea?
1) increased osmotic load
2) increased secretion
3) inflammation
4) decreased absorption time
When does Osmotic diarrhea occur?
1) When unabsorbable, water-soluble solutes remain in the bowel, where they retain water.
2) Sugar intolerance - including lactose intolerance caused by lactase deficiency
3) w/ use of poorly absorbed salts( Mg sulfate, Na phosphates) as laxatives or antacids
Ingestion of large amounts of the hexitols (e.g, sorbital, mannitol) are used as sugar substitutes cause what? Why?
Osmotic diarrhea as a result of their SLOW absorption and stimulation of rapid small-bowel motility (“dietetic food” or “chewing gum” diarrhea)
What can eating too much of some foods, like certain fruits can cause?
Osmotic diarrhea
What is secretory diarrhea? What does it include ?
Occurs when the small & large bowel secrete more
electrolytes and water than they absorb.
-Secretagogues include bacterial toxins (e.g–in cholera), enterophogenic viruses, bile acids & unabsorbed dietary fat
What is exudative diarrhea? What does it include ?
Occurs with several mucosal diseases (e.g.–reginal enteritis, ulcerative colitis, lymphoma, cancer) that cause mucosal inflammation, ulceration, or tumefaction.
What results from exudative diarrhea?
Outpouring of plasma, serum proteins, and mucus increases fecal bulk and fluid content.
***Involvement of the rectal mucosa may cause urgency and increased stool frequency because the inflamed rectum is more sensitive to distention.
When does 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 factors decrease the 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?
Defined as the infrequent passage of stools
***Difficulty w/ this definition arises from the many individuals variations of function that is normal
When does problems increase with constipation?
With age
***There is a sharp rise in health care visits for constipation after 65 years of age
Constipation can occur as a ?
primary problem or as a problem associated with another disease condition
What are some common causes of constipation?
1) failure to repsond to the urge to defecate
2) inadequate fiber in the diet
3) inadequate fluid intake
4) weakness of the abdominal muscles
5) inactivity and bed rest
6) pregnancy
7) hemorrhoids
What are some disorders associated with chronic constipation?
Neurologic disease such as:
1) spinal cord injury
2) Parkinson’s disease
3) Multiple Sclerosis
4) Endocrine disorders: hypothyroidism or diabetic neuropathy
5) obstructive lesion i the GI tract
What drugs are associated with chronic constipation?
Opiates, anti-cholinergic agents, valium channel blockers, diuretics, iron supplements and aluminum antacids tend to cause constipation
What is Irritable Bowel Syndrome (IBS)?
Used to describe a functional GI disorder characterized by a variable combination of chronic and recurrent intestinal symptoms not explained by structural or biochemical abnormalities.
What does evidence suggest about IBS?
10-20% of people in Western counties have the disorder, most do not seek medical attention