Gastrointestinal

GI tract is divided into:

* --------
* oropharynx, esophagus, stomach
* -------
* intestines, colon, rectum

upper GI tract, lower GI tract

the coordinated symmetrical contraction and relaxation of muscles that propagates in a wave down the GI tube

peristalsis

four major functions of the GI

digestion and movement of food, absorption of nutrients, elimination of wastes, mucosal immunity (produces IgA)

Basic structure of GI

* --------
* inside the tube, epithelium, basement membrane, lamina propria (connective tissue, small blood vessels, nerves and lymphatics, thin muscle layer)
* ---------
* connective tissue, blood vessels, nerves, lymphatics, secretory glands
* --------
* two layers of smooth muscle (circular inner, lengthwise outer)
* ------
* outside of the tube
* connective tissue with larger blood vessels, nerves, and lymphatics

mucosa, submucosa, muscularis, serosa

diseases tend to occur in specific ------ of each organ of the GI system

region

difficulty swallowing

dysphagia

Indigestion → discomfort in upper abdomen with bloating and gas

dyspepsia

Regurgitation of stomach gastric fluids into esophagus

reflux

Gastroesophageal reflux disease ,chronic reflux injures esophagus

GERD

burning chest pain/heartburn, can mimic heart attack

pyrosis

* vomiting up blood
* significant upper GI hemorrhage/ruptured vessel still has fresh blood
* slow bleed causes blood to be degraded by stomach acid, vomit has coffee ground appearance

hematemesis

Black tar-like stool caused by significant upper GI bleed

melena

Test that detects blood in the stool

fecal occult blood test

Congenital esophageal defect

* failure to develop and results in dead end pouch
* results in vomiting

esophageal atresia

Congenital esophageal defect

* abnormal connection between lungs and GI tract
* results in either food in the lungs (aspiration pneumonia from GI bacteria) or bloating due to air in stomach

tracheo-esophageal fistula

Congenital esophageal defect

* narrowing of the tube
* results in dysphagia (difficulty swallowing)

esophageal stenosis

Acquired or Congenital esophageal defect

* the LES is a thickening of esophageal wall and diaphragm muscles prevents the stomach contents from entering esophagus
* relaxation of the LES can cause reflux of gastric fluids
* many substances (alcohol, caffeine, tobacco) can relax the normal muscle tone of the LES

Relaxation of the lower esophageal sphincter (LES)

Acquired or Congenital esophageal defect

* defect in the opening of the diaphragm, causes part of the cardia region of the stomach to protrude into the thoracic cavity
* hernia can interfere with normal LES function and cause reflux

hiatal hernia

acquired esophageal defect

* dilation of the veins in the distal/lower thoracic esophagus
* caused by high pressure in the veins due to portal hypertension caused by liver cirrhosis
* backs up blood supply producing varices in the esophagus
* can also occur in rectal cavity causing hemorrhoids
* rupture can cause massive bleeding and death, common cause of death in cirrhosis
* treated by band ligation
* tie off vessel with surgical band to stop blood flow, causing varices to regress

esophageal varices

Esophageal disease caused by caused by GERD (most common) and infections

* symptoms = dysphasia and pyrosis


* Infections
* usually in immunocompromised
* viruses (herpes, CMV)
* fungus (C. albicans)
* GERD
* caused by chronic reflux due to LES dysfunction
* reflux of stomach acid damages and inflames the squamous epithelium of the esophagus can cause fibrosis and narrowing
* long term GERD causes metaplasia of the distal region from squamous to gastric epithelium = **Barrett esophagus**

Esophagitis

Metaplasia of the distal region from squamous to glandular gastric epithelium

* chronic GERD can predispose to develop **adenocarcinoma of esophagus**

Barret esophagus

Two major types of esophageal carcinoma

Squamous cell carcinoma (SCC) and adenocarcinoma (AC)

Adenocarcinoma of the esophagus is the most common type of esophageal cancer in the ------ , and squamous cell carcinoma is the more common --------

US, worldwide

Risk factors for esophageal carcinoma

* nitrosamines in food =
* excessive or long term alcohol and tobacco use =
* possible environmental/occupational causes =
* long standing GERD =

* SCC
* AC and SCC
* SCC
* AC

Type of esophageal cancer

* most in mid-upper part of esophagus, uncommon in the US
* develops from squamous epithelium
* associated with diet and environment

squamous cell carcinoma

Type of esophageal cancer

* found in lower part of esophagus near LES, and more common in the US
* develops from gastric glands in region of Barrett esophagus
* associated with long-standing GERD

adenocarcinoma

regions of the stomach

* ----- = region below LES where stomach begins
* ----- = upper region that stores gas and indigested food
* ----- = largest part where the main digestion occurs
* ----- = narrowing of the stomach to funnel contents to the pylorus
* ----- = controls movement of food into duodenum

cardia, fundus, body/corpus, antrum, pylorus

Stomach cell types

* ------ = mucus, protects stomach lining
* ------ = produces gastric acid (HCl) and intrinsic factor
* intrinsic factor is needed to absorb vitamin B12, required for RBC production
* ------- = pepsinogen, protease precursor
* ----- = somatostatin, inhibits acid secretion
* ----- = gastrin, stimulates acid secretion

goblet

parietal cells

chief cells

D cells

G cells

gastric mucosa is required for ---------

* normal blood flow to stomach
* intact mucus later and normal mucus production
* normal acid and bicarbonate production
* normal gastric and somatostain secretion

gastric mucosa can be ------ by:

* H. pylori
* increased acid production
* aspirin and NSAIDs
* smoking and alcohol
* ischemia and trauma

protection, damaged

Type of gastritis

* relative short duration but can be severe
* usually caused by irritant exposure or trauma
* irritants often produce **erosions** of the mucosa (superficial ulcers)
* trauma often results in **stress ulcers** (multiple small ulcers)
* often results in pain, vomiting/hematemesis, or dyspepsia
* **severe acute cases can cause significant blood loss**

acute gastritis

type of gastritis

* long duration and often produces ulcers
* infection with H. pylori is the most common cause

chronic gastritis

type of gastritis

* destruction of the mucosa results in gastric atrophy
* most often occurs in the elderly, caused by autoantibodies to parietal cells
* can result in pernicious anemia
* decreased intrinsic factor due to death of parietal cells, which leads to decreased vitamin B12 absorption in the gut resulting in anemia

autoimmune atrophic gastritis

Three types of gastritis

acute, chronic, and autoimmune atrophic gastritis

Umbrella term for a chronic condition

* gastric ulcer is one type, present in the stomach
* epigastric pain 1/2-1 hour after meal
* duodenal ulcer is one type, present in the duodenum
* pain 2-4 hours after a meal
* very common condition with risk factors such as NSAIDs, smoking, and drinking
* H, pylori is associated with almost all cases
* does NOT directly damage mucosa → alters gastric mucosa allow acid to produce ulcer at infection site
* pathology
* round, solitary punched out appearance that can extend deep into submucosa
* significant bleeding can occur is ulcer erodes a blood vessel or peritonitis if ulcer erodes stomach wall/perforation into peritoneal cavity

peptic ulcer

type of gastrointestinal cancer

* accounts for almost all stomach cancers
* originates from glandular epithelium
* uncommon in the western hemisphere, but very common worldwide
* risk factors are nitrosamines in food, cigarettes, and chronic H pylori infection
* tumors often invade peritoneal cavity

adenocarcinoma

adenocarcinoma of stomach, two different tumor types

* ------ = grows and fills lumen of stomach
* ----- = infiltrates the stomach wall and encases it with cancer, producing a rigid, thick, leather bottle appearance

fungating, diffuse

Two major functions of intestine

* remember ileum has extensive lymphoid tissue (Peyer’s patches) that contribute to mucosal immunity

food absorption and produce large amounts of IgA for mucosal immunity

Enterocytes of the intestine have a very large -------- for absorption

* mucosal folds, villi, amd microvilli
* HUGE surface area for nutrient absorption

surface area

Intestinal cell types

* stem cells
* paneth cells = ------
* located at bottom of crypts
* goblet cells
* dividing cells
* enteroendocrine cells = --------
* mature enterocytes = -------
* majority of cells in intestine

immune functions, release hormones, absorbs nutrients

process of enterocyte epithelial cells dying by apoptosis, detach, and shedding into lumen

* conveyer belt → cells divide towards bottom of crypts, then move up as they mature until they reach the top of the crypt → detach and shed into lumen

anoikis

Tumors of the intestine are very ------ and most are ------

rare, benign

* disease of the intestine caused by infections in the intestine, usually viral or bacterial
* results in cramping, gas, and diarrhea
* severe bacterial infections such as cholera and salmonella can be fatal if not treated

gastroenteritis

* disease of the intestine, an immune reaction against the wheat protein **gliadin**
* NOT AUTOIMMUNE
* Tc cells responding to gliadin kill enterocytes and destroy villi, most often in duodenum and jejunum
* results in decreased absorption and malnutrition
* treatment is avoid gluten
* gliadin + glutenin = gluten

Celiac disease

A serious medical emergency where part of the intestine slides into an adjacent part of the intestine/colon

* this blocks food or fluid from passing through, and can stop blood supply to this part of the intestine
* usually affects infants and young children, and normally males
* in adults this can be caused by tumors, polyps, or scar tissue
* treatment is surgery ASAP

intussusception

Disease of the colon that develops due to either Fecalith/hardened stool blocking the entrance to the appendix causing inflammation (major cause) or hyperplasia of lymphoid tissue (appendix is lymphoid tissue)

* obstruction leads to ischemia and overgrowth of gut bacteria
* causes pain in the lower right quadrant, fever, leukocytosis
* surgical treatment required since can rupture and cause peritonitis
* interval appendectomy = if appendix already ruptured will be treated with ATBs then have it removed
* before modern surgery appendicitis was always fatal

acute appendicitis

Broad category that contains two distinct diseases (Crohn’s disease/regional enteritis and Ulcerative colitis

* common features of CD and UC
* idiopathic complex diseases with both genetic and autoimmune components
* chronic relapsing diseases
* affects women more
* can effect any age, but peak incidence is mid-20s
* both have intermittent diarrhea but severity is variable
* medical treatment is steroids, antibiotics, and new targeted biologics (anti-cytokine drugs)
* CD
* less common than UC
* usually more severe symptoms and pathology
* 30% have lesions outside GI tract
* UC
* 3x more common than CD
* usually starts with mild symptoms

inflammatory bowel disease

Type of IBD

* Can affect ANY part of the GI tract, most often terminal ileum
* Transmural inflammation
* can extend through submucosa, muscle layer, and serosa to perforate the tube and form **fistulas** between loops of bowel


* **inflammation is discontinuous**, islands of inflammation known as **skip lesions**
* linear ulcerations of the mucosa result in a **cobblestone**-like appearance when examined grossly
* **granulomas** in CD lesions
* no or slight increase in cancer risk
* AVOID surgery → can make worse

Crohn’s disease

type of IBD

* affects **only colon and rectum**, starts in the rectum and progresses up the colon
* **mucosal inflammation** → it is confined to the mucosa, and does not extend to the submucosa
* **inflammation is continuous**
* strips large areas of the colonic submucosa causing the remaining normal mucosa to resemble polyps, known as **pseudopolyps**
* NO granulomas in these lesions
* **increased** risk of colon cancer
* surgery (colonectomy) can be **curative**

ulcerative colitis

An abnormal out-pouching in the wall of the colon

* very common, incidence increases with age
* thought to be caused by increased pressure in the colon wall and/or weak spots in the colon wall
* occur mostly in distal colon, can have just one or many…. these can become inflamed leading to diverticulitis

diverticulosis

Inflammation of diverticula, due to obstruction with feces

* symptoms are similar to appendicitis, but usually on the left side
* complications include
* rupture = peritonitis
* scarring = stricture and obstruction
* fistulas
* massive bleeding from erosion of a blood vessel

diverticulitis

Type of colon polyp

* most common non-cancerous polyp
* small and flat

hyperplastic polyp

Type of colon polyp

* most common pre-neoplastic polyp
* starts as benign growth, but some can transform into cancer
* can be sessile (Flat) or pedunculated (Raised)
* -------- adenoma = pedunculated, 80% are benign but some can develop into adenocarcinoma
* ----- adenoma = sessile, some are benign but half may develop into adenocarcinoma
* \

adenomatous polyp, tubular, villous

nearly all colon cancer cases develop from ------- polyps, and of those are the --------

adenomatous, villous

Main type of colon cancer

* accounts for >95% of colon cancers
* 3rd most common non-skin cancer in US for men and women, and 3rd cause of cancer death in men and women in US
* associated with diet high in animal fat and low in fiber
* most cases are distal colon, and diagnosed in older adults
* Lynch syndrome (hereditary non-polyposis colorectal cancer) is an inherited early onset form of this cancer
* symptoms = changes in bowel habits, mild anemia due to slow blood loss around tumor, abdominal pain, unexplained weight loss

Adenocarcinoma

Staging of colon cancer (and others) depends on three factors

tumor (size and invasion), nodes (number of lymph nodes invaded by cancer cells), and metastasis (usually liver in colon cancer)

\------- has helped greatly in diagnosis and management of colon diseases

* easier access = more biopsies = better and earlier diagnosis
* prognosis is goof if colon cancers are detected at stage 1 and 2
* screening via this method has greatly reduced incidence by removal of cancerous polyps, and improved survival by earlier detection

colonoscopy