Small and Large Intestine Flashcards
Small Intestine
consists of three segments: the Duodenum, the Jejunum, and Ileum. It is the primary site of digestion and nutrient absorption. It’s surface area is greatly increased by its circular folds, villi and microvilli.
Large Intestine
COLON. allows for the absorption of water and electrolytes.
Haustra
folds of circular muscle creating sac like segments along the colon
GALT
GI Associated Lymphoid Tissue.
Includes Kupfer cells (fixed macrophages in the liver.) From individual cells (intraepithelial lymphocytes) to large “clumps” of immune cells (Peyer’s patches in the ileum.) Plus all the lymph nodes outside the stomach, small & large intestine, etc. Reflects the fact that the gUT is the place we sense the world around us. THE STOMACH IS THE MOST COMMON “EXTRANODAL” SITE FOR LYMPHOMA.
Diarrhea
a volume of greater than 150-200ml per 24 hours. Osmotic diarrhea occurs when carbohydrates (lactose, sorbitol) or minerals (such as magnesium citrate) create an osmolar gap. Water follows into the lumen to reduce this situation. Secretory diarrhea may be secondary to toxins from infectious bacteria (Yersinia, CAMPYLOBACTER JEJUNII, Shigella, Salmonella) or gut hormones.
Constipation
a problem of the large intestine. the causes of decreased stool frequency or increased consistency are many including structural (tumor, adhesion), hormonal (hypothyroidism, diabetes), neurologic (Hirschsprung disease) and more. THE MOST COMMON CAUSE IN THE WESTERN WORLD IS POOR DIETARY FIBER INTAKE.
Inflammatory Bowel Disease (IBD)
a chronic inflammation of the bowel and often has a pattern of familial occurrence. There may be many manifestations of IBD in systems outside of the GI tract.
Causes of IBD
Genetic susceptibility
Immune dysregulation
Environmental triggers
The hygiene Hypothesis
People in areas endemic for intestinal helminths and other intestinal pathogens are less likely to get IBD.
Inflammatory bowel diseases
ulcerative colitis and ulcerative proctitis
Crohn’s disease
Genetic, inflammatory, environmental
ulcerative colitis
chronic ulcerative colitis most commonly develops in young adults. peaking in incidence in the 3rd decade.
UC is a disease of the lining or MUCOSA of the colon. it may involve the entire organ (pancolitis) or be limited to the distal aspect (left sided colitis). a subset of patients have involvement of the rectum alone and never progress further (ulcerative proctitis).
symptoms of ulcerative colitis
diarrhea
bleeding
urgency
pain with defecation (tenesmus)
c
the characteristic microscopic finding in UC is the CRYPT ABSCESS. over time, raised islands of normal mucosa form and are known as pseudopolyps.
severe, long standing (> 15 yrs) IC are at a significant risk for developing colon cancer.
Extracolonic manifestations, co-exist problems, ex. arthritis, skin lesions etc.
therapy: colectomy
Crohn’s disease CD
most often arises in adolescents and young adults. it may be seen in family clusters. rising.
it may involve any part of the digestive tract from mouth to anus. it is most often seen in the terminal ileum and right side of the colon (45%). about 1 in 5 cases involves the colon alone.
Presentations of CD
is a process that is TRANSMURAL, involving the full thickness of the bowel wall in contrast to ulcerative colitis.
ileal involvement *strictures* *fistulas* *transmural involvement* granulomas linear clefts
Clinical presentations: fever, abdominal pain, and diarrhea. early symptom is quite non specific.
the risk of colon can ver is increased with crohn’s disease
Treatment of CD
no curable treatment
steroids. sulfasalazine and immunosuppressives such as azathioprine may be used. surgery is often helpful but mostly have recurrence.
Colon
..
Diverticulosis
mucosal outpouchings of the lining of the large bowel (technically pseudodiverticula).
caused in part by low dietary fiber and the higher pressures the colon makes to propel stool forward.
acquired herniation of mucosa/submucosa through the muscular of the colon.
striking greographic variation: common in the West, unusual in Africa, Asia.
More common in higher SES groups
Age: 10% of adult population in U.S.
1/3 to 1/2 by age 60.
stool balls in the side pockets of the colon……low grade infection of even small perforations with subsequent abscess formation. chronic infections can lead to scarring and strictures.
Clinical aspects of diverticulosis
80% no symptom.
bleeding.
the other common cause of lower GI bleeding is from ANGIODYSPLASIA also known as vascular ectasia
complication–infection–diverticulitis
fecalith -- inspissated stool in a pocket. cause low grade inflammation leads to micro-perforation Typical symptoms left lower quadrant pain Increased WBC Generalized peritonitis abscess
Diverticulitis treatment
clear liquids
low fiber diet (during an episode)]
antibiotics: metronidazole/ciprofolxacin
colon cancer
the second most common cause of cancer in men and (third most common cause in) women in the Western world.
Presentation of colon cancer
early (curable) colon cancer has NO SYMPTOMS
It’s COMMON ==> screen it early
may cause very subtle, hidden (occult) bleeding and sreening for this with stool guiaic (hemoccult) cards should be performed yearly after age 50.
gross bleeding, obstruction, perforation, or a fistula.
risk factors for colon cancer
age diet and geography family history chronic colitis adenoma previous colorectal neoplastia
adenoma – carcinoma sequence
normal mucosa –> adenoma –> severe dysplasia –> cancer
polyp
a mass that protrudes into the lumen of the gut. most commonly in colon. not all polyps have the potential of becoming a malignancy. examples: hyperplastic, juvenile (hamartomatous), inflammatory, and lymphoid polyps. adenomatous polyps (adenomas) can progress to adenocarcinoma.
Screening for colon cancer
colonoscopy: sensitive, specific, allows for therapeuties, expensive, requires sedation.
virtual colonography (CT colonography)
Stool genetic analysis (cologuard)
family adenomatous polyposis FAP
the autosomal dominant gene, adenomatous polyposis coli (APC) is due to a specific genetic defect found on chromosome 5. The gene has been identified and blood samples can be screened for it. Thousands of polyps develop in the colon and colon cancer is inevitable by age 40. Polyps also develop in the stomach and small bowel.
Hereditary non-polyposis colon cancer
refers to patients with relatively small numbers of polyps but clustering of colon, pancreas, ovary, and uterus cancers. It is a defect in the mis-match repair gene and it allows for mistakes to happen during replication of the DNA.
