GI SYSTEM

what is the purpose of GI tract?

-Ingest food
-Propulsion of food and wastes from the mouth to the anus
=Secretion of mucus, water, and enzymes
-Mechanical AND chemical digestion of food particles
-Absorption of digested food
-Elimination of waste products by defecation

The stomach...

-is lined by mucusa
-has bicarbonate as a buffer
-has gastrin hormone

What does the hormone gastrin do?

-produced in stomach
-produced by G cell in pyloric region
-stimulates gastrin glands that lead to production of HCl and pepsinogen

what are the different gastric glands?

-chief cells
-parietal cells
-mucous cells
-electrolytes and bicarbonate

what do chief cells do?

-secrete pepsinogen--HCl
-HCl has pepsin (protein digest)

what do parietal cells do?

-secrete HCl and intrinsic factor

What is the role of the intrinsic factor?

-allows for absorption of vitamin B12 by small intestine
-lack of B12=pernicious anemia since B12 is necessary for hemoglobin

what is the role of mucous cells?

-secrete mucous and bicarbonate which create the protective layer

What keep the duodenum bacterial numbers to a minimum?

Bile acid secretion, motility, and antibody production

where can you find anaerobic bacteria?

distal to ileoceccal valve, in the colon

what does digestion do?

-breaks down food mechanically and chemically
-extracts macronutrients
-absorbs digested components
-forms barrier against microorganisms.

what is absorption affected by?

-Competition for carriers can block nutrients
-Saturation of carriers can inhibit absorption
-Absorption can be enhanced or inhibited (EX: vit C increases absorption of iron)
-Dietary fat is needed to absorb fat soluble vitamins
-Gastric pH
-Bioavailability- mineral unbound to be absorbed.

iron bioavailability

-can be absorbed in the bound state

what role do intestinal cells play in absorption?

-regulate and promote max absorption by limiting potential for nutrient toxicity

what is hunger induced by?

low glucose of lack of food

what occurs with insulin during intake of foot?

-food in GI track results in insulin secretion.
-insulin then reduces appetite

What does cholecystokinin do?

-fat stimulated release of cholecystokinin,
-cholecystokinin leads to satiety

where are lipids and fat soluble vitamins stored?

liver and glycogen

if you have an increase in fat stores, what is released?

-increases fat stores releases leptin
-leptin suppresses appetite, increases energy expenditure and metabolism

What does the hypothalamus do?

-it regulates metabolism and appetite
-hormones signal hypothalamus

what hormones stimulate appetite and weight?

-ghrelin
-peptide YY

which hormones are anorexins?

-insulin
-leptin

what suppresses appetite?

-serotonin
-cocaine

define anorexia

-lack of a desire to eat despite physiologic stimuli that would normally produce hunger

Define vomiting

-the forceful emptying of the stomach and intestinal contents through the mouth
-Several types of stimuli initiate the vomiting reflex
-Chemical trigger zone

Define nausea

-subjective experience that is associated with a number of conditions
-common symptoms are hypersalivation and tachycardia

Define retching

Nonproductive vomiting

define projectile vomiting

-spontaneous vomiting that does not follow nausea or retching

define constipation and its clinical manifestations

-infrequent or difficult defecation
-Fecal impaction: Hard, dry stool retained in rectum
-Two of the following for at least 3 months: straining, lumpy/hard stools, sensation of incomplete emptying, manual maneuvers to facilitate stool, less than 3 bowel mov per week

what can contribute to constipation?

-Neurogenic disorders
-Low-residue/fluid diet
-Sedentary lifestyle
-Hypothyroidism
-Functional problems
-Excessive use of antacids
-Opioids
-Gastric paresis

what is normal transit constipation?

-Normal rate of stool passage, but difficulty with stool evacuation from low-residue, low-fluid diet and sedentary lifestyle

What is slow transit constipation?

impaired colonic motor activity with infrequent bowel movements and straining

what is secondary constipation?

-From an actual disease processes, diet, medications

What is the valsalva maneuver?

-The increase of abdominal pressure reduces venous return which causes bradycardia and a decrease in cardiac output, this eventually leads to a transient decrease in BP
-may be fatal

what are some problems related to constipation?

-Nutrition
-GI pain
-Diverticulosis
-Fecal impaction (obstipation)
-Colonic perforation
-valsalva maneuver

osmotic diarrhea

Non-absorbable substance draws water into the GI tract by osmosis
-causes large-volume diarrhea

secretory diarrhea

-form of large-volume diarrhea
-Excessive mucosal secretion of chloride or bicarbonate rich fluid or inhibition of sodium absorption

motility diarrhea

excessive motility decreases transit time, mucosal surface contact, and opportunities for fluid absorption

What can diarrhea cause?

-fluid and electrolyte imbalance: can lead to dehydration, electrolyte imbalance (hyponatremia, hypokalemia), metabolic acidosis and weight loss
-Impaired skin integrity
-Acute pain
-Infection transmission
-TREATMENT: fecal transplantation

Parietal pain (somatic pain)

-from the parietal peritoneum
-more localized and intense

visceral pain

-arising from a stimulus acting on an abdominal organ
-poorly localized
-dull vague and difficult to describe (cramping, fullness)

referred pain

-visceral pain felt at some distance from the organ involved (gallbladder pain is felt in the back between scapulae)

from where does abdominal pain come?

-From mechanical, inflammatory or ischemic alterations

what organs are involved in upper GI bleeding?

-Esophagus, stomach, or duodenum

what organs are involved in lower GI bleeding?

-Jejunum, ileum, colon, or rectum

What is hematemesis a sign of?

-bloody vomit
-esophageal varies or duodenal ulcers

What is hematochezia?

bright red blood from rectum

What is melena and what does it indicate?

-Black tarry stool indicative of an upper GI bleed

What does occult blood in the feces mean?

-not visible
-Bleeding somewhere in the GI tract

What is dysphagia?

-difficulty swallowing
-can manifest as an upper or lower esophageal obstruction, regurgitation, unpleasant taste, V and weight loss
-can have mechanical obstructions or functional dysphagia

Achalasia

-failure of the lower esophagus sphincter muscle to relax
-denervation of smooth muscle in esophagus
-related to dysphagia

GERD (gastroesophageal reflux disease)

-acid and pepsin reflux from the stomach go into esophagus and cause inflammation
(esophagitis)
-resting tone of lower esophageal sphincter is lower than normal due to transient relaxation or weakness of sphincter.
-worsened by delayed gastric emptying
-increasing abdominal pressure contributes to GERD:things such as v, coughing, lifting, obesity, preg

how to manage GERD?

-lose weight
-no big, fatty meals
-no laying down after means, HOB elevated
-no alcohol, caffeine, nicotine

what are manifestations of GERD:

-Heartburn, regurgitation of chyme, and upper abdominal pain within 1 hour of eating
-Esophageal pH test will show low pH=gastric acid reflux.
*esophagus should be alkaline

What is a hiatal hernia?

-It is when the upper part portion of the stomach herniates through the esophageal hiatus of the diaphragm, into the chest.
-can be asymptomatic or the patient can experience heartburn, regurgitation, dysphasia and epigastric pain

what is a sliding hiatal hernia?

-proximal portion of the stomach slides through hiatal opening
-proximal stomach portion moves into the chest through an opening in the diaphragm for the esophagus and vagus nerves.
-most common

What is a paraesophageal/rolling hiatal hernia?

-greater curvature of stomach herniates through second opening in diaphragm

What is a pyloric obstruction?

-the blocking or narrowing of the opening between the stomach and the duodenum
-can be acquired or congenital

what are manifestation of pyloric obstruction?

-Epigastric pain and fullness
-N/V
-Succussion splash
-prolonged obstruction can lead to malnutrition, dehydration, and extreme debilitation

what is an intestinal obstruction?

-any condition that prevents the flow of chyme through the intestinal lumen or failure of normal intestinal motility in the absence of an obstructing lesion

what is an ileus?

-an obstruction of the intestines
-can be a simple or functional obstruction

if you have an obstruction in the pyloris what type of vomitus will you have?

-early, profuse vomiting of clear gastric fluid

if you have an obstruction in the proximal small instestine what type of vomitus will you have?

-mild distention and vomiting of bile-stained fluid

if you have an obstruction in the lower small instestine what type of vomitus will you have?

-pronounced distention because a greater length of intestine is proximal to the obstruction
-no vomit or may occur later and contain fecal material.

what is acute gastritis?

-erosion of epithelial surface from topical exposure

what is chronic fundal gastritis?

-causes gastric atrophy
-Associated with pernicious anemia, decreased HCl, antibodies

what is chronic antral gastritis?

-more common
-not associated with pernicious anemia, decreased HCl, antibodies

What is peptic ulcer disease?

-A break or ulceration in the protective mucosal lining of the lower esophagus, stomach, or duodenum
-can be acute or chronic
-can be superficial or deep

What is a duodenal ulcer?

-Most Common peptic ulcer
-*Causes:
-H. pylori infection (promote inflammation)
-Hypersecretion of stomach acid & pepsin
-Use of NSAIDs
-Rapid gastric emptying
-high gastrin levels
-cig smoking increasing acid production

what is a gastric ulcer?

-develop in antral region of stomach, next to acid-secreting mucosa
-primary defect is an increased mucosal permeability to H+ ions
-gastric secretion is normal or less than normal

what is a stress ulcer?

-peptic ulcer related to severe illness, neural injury, or systemic trauma
-Stimulation of vagal nuclei leads to a decrease in mucosal blood flow (mucosal ischemia) and hypersecretion of stomach acid
-can be ischemic ulcer: hemorrhage, sepsis,HF, multysystem trauma
-can be cushing ulcer: head trauma or neurosurgery

what is a curling ulcer?

-stress ulcers that develop as a result of a burn injury

What is dumping syndrome?

-Rapid emptying of chyme from surgically created, residual stomach into small intestine
-occurs 10-20 minutes after eating
-complication of partial gastrectomy or pyloroplasty surgery
-can be late or early dumping. late has diaphoresis

Why does dumping syndrome occur?

-there is a loss of gastric capacity,
-loss of emptying control,
-loss of feedback control by the duodenum when it is removed

How does dumping syndrome present?

-craping pain, N/V/D, weakness, pallor, hypotension
-alkaline reflux gastritis: bile and pancreatic secretions
-afferent loop obstruction: due to adhesions
-diarrhea-osmotic
-weight loss: carbs intolerance
-anemia: iron malabsorption and pernicious anemia

what are treatments for early and late dumping

-frequent small meals high protein, low carbs
-drink fluids b/t meals instead of at mealtime
-reclining on left side after eating

What are the malabsorption syndromes?

-interference w/ nutrient absorption in small intestine
-maldigestion and malabsorption occur together
-maldigestion: failure of chemical process of digestion
-malabsorption: failure of mucosa to absorb digested nutrients

what are causes of malabsorption syndrome

-pancreatic enzyme insufficiency
-lactase deficiency
-bile salt deficiency
-fat-soluble vitamin deficiencies

how does pancreatic insufficiency cause malabsorption?

-failure to produce enough pancreatic enzymes: lipase, amylase, trypsin or chymotrypsin
-Causes include pancreatitis, pancreatic carcinoma, pancreatic resection, and cystic fibrosis
-Main problem: Fat maldigestion
-patient will exhibit fatty stools and weight loss
-In children - failure to grow

how does lactase deficiency cause malabsorption?

-unable to break down lactose into monosaccharides, prevents lactose digestion
-fermentation of lactose by bacteria causes gas (cramping pain, flatulence, etc.) and osmotic diarrhea

how does bile salt deficiency cause malabsorption?

-decreased production or secretion of bile satls
-bile salts are needed to emulsify and absorb fats
-bile salts are made from cholesterol in liver
-results from disease of liver, bile duct, ileum; ileus
-Poor intestinal absorption of lipids causes fatty stools, diarrhea, and loss of fat-soluble vitamins (A, D, E, K)

how does fat-soluble vitamin deficiency cause malabsorption?

-Vitamin A- night blindness
-Vitamin D- decreased calcium absorption, bone pain, osteoporosis, fractures
-Vitamin K- prolonged prothrombin time, purpura, and petechiae
-Vitamin E

inflammatory bowel disease (IBD)

-Chronic, relapsing inflammatory bowel disorders of unknown origin.
-Can be due to genetics, environmental factors, alterations of epithelial barrier functions, immune reactions to intestinal flora, varying phenotypes
-EX: Ulcerative colitis and Crohn's disease

What is ulcerative colitis?

-Chronic inflammatory disease that causes ulceration of the colonic mucosa: sigmoid colon and rectum-no skip lesions
-Hyperemic colon, erosions occur which form ulcers that can become infected
-increased risk for colon cancer
-mucosal layer is affected
-bloody stools and antineutrophil cytoplasmic antibodies are common

What is Crohn's disease?

-also called granulomatous colitis, ileocolitis or regional enteritis
-affects any part of digestive tract, from mouth to anus
-causes skip lesions (inflamed tissue alternating with ulcerated tissue
-affects entire intestinal wall
-granuloma are common w/ cobblestone appearance
-abdominal pain, steatorrhea and antisaccharomyces cerevisiae antibodies are common
-smoking worsen disease
-can result in anemia due to malabsorption of B12 and folic acid

what is diverticula?

Herniations of mucosa through the muscle layers of the colon wall, especially the sigmoid colon

what is diverticulosis?

asymptomatic diverticular disease

What is diverticulitis?

-The inflammatory stage of diverticulosis
-can become infected, rupture
-Fever, leukocytosis

what are predisposing factors to diverticular disease of colon?

-Older age, genetics, obesity, smoking, diet, lack of physical activity, and medications

What are the clinical manifestations of diverticular disease?

-Low cramping abdominal pain, diarrhea, constipation, distension, flatulence
-Diverticulitis: Fever, leukocytosis

what are treatments for diverticular disease?

-increase fiber to lower colonic pressures, improve transit time and symptoms
-uncomplicated: bowel rest and antibiotics
-surgical resection

What is appendicitis?

-inflammation of the vermiform appendix
-can be due to obstruction, ischemia, increased intraluminal pressure, infection, ulceration

What can appendicitis cause?

-epigastric and RLQ pain
-rebound tenderness - McBurney's point
-fever, elevated WBC
-Peritonitis

What is irritable bowel syndrome?

-crampy abdominal pain, associated with D, constipation or both
-young women w/ anxiety, depression
-Can be due to visceral hypersensitivity, abnormal GI motility and secretion, enteritis, food allergy, psychosocial factors

How does irritable bowel syndrome present?

bloating, pain relieved by defecation, change in stool-loose, watery or pellet like

What is vascular insufficiency?

-blood supply to stomach and intestine is compromised
-can be an acute occlusion of mesenteric artery blood flow: due to dissection or emboli-presents with pain, rigid abdomen and bloody diarrhea
-can be chronic mesenteric insufficiency: due to HF-presents with colicky pain after meals

what are manifestations of intestinal vascular insufficiency?

-Abdominal pain, fever, bloody diarrhea, hypovolemia, leukocytosis, shock

What is the portal system?

low pressure system that facilitates blood flow through liver vasculature

What is portal hypertension?

-abnormally high blood pressure in the portal venous system due to resistance to portal blood flow
-the problem can be prehepatic? intrahepatic? or posthpatic?

what are consequences of portal hypertension?

-Varices: distended, tortuous collateral veins *found in lower esophagus, stomach, rectum. *can rupture, causing major hemorrhage

-Splenomegaly: increased pressure in splenic vein

-Ascites: increased pressure in mesenteric veins. *Hydrostatic pressure forces fluid into peritoneum