Gastrointestinal System Anatomy

Gastrointestinal (GI) System Review

• The GI tract goes from the mouth to the anus.
• The GI tract is responsible for digestion.

Upper GI

• Mouth: Chewing, enzyme-assisted breakdown of food occurs.
• Esophagus: Food is propelled to the stomach.
• Stomach: Churning and storage of food takes place.

Lower GI

• Small Intestine: Nutrient absorption and hydrolysis happens here.
• Large Intestine: Absorbs water, ions, and vitamins.
• Rectum: Stores waste before defecation.
• Anus: Expels waste.

Chyme and the Pyloric Sphincter

• Chyme flows from the stomach through the pyloric sphincter, also known as the lower esophageal sphincter, into the duodenum.
• The pyloric sphincter controls the passage of food into the small intestine/duodenum.
• It is a muscular valve at the bottom of the stomach.
• The small intestine is the "door out" of the stomach.
• The pyloric sphincter regulates the flow of partially digested food (chyme) from the stomach into the small intestine.
• It prevents food from entering the small intestine too quickly.
• The pyloric sphincter protects the small intestine from stomach acid and other harmful substances.

Small Intestine Details

• Narrow, long, about 2.5 times an individual's height.
• Consists of the duodenum, jejunum, and ileum
• Absorption mainly occurs in the small intestine.
• Long, circular folds and winding tubes enhance the surface area for digestion and absorption.

Liver

• Performs metabolic and regulatory tasks.
• Produces bile, which enters the duodenum aiding in digestion.

Bile

• Bile duct: Connects the liver to the duodenum, bringing bile.
• Bile: Enters the duodenum and helps emulsify fats.
• Gallbladder: Stores bile.

Pancreas

• Pancreatic duct: Releases inactive pancreatic enzymes into the small intestine.
• Pancreatic juice contains enzymes for breaking down food.
• The bile and pancreatic ducts merge with the small intestine.

Cecum and Appendix

• Cecum: Attaches to the large intestine.

Large Intestine (Colon)

• Ascending Colon: Absorbs water, electrolytes, vitamin K, vitamin B, and acetylcholine.
• Transverse Colon: The area where the contents of the GI tract cross the abdomen to the other side.
• Descending Colon: Where contents are stored before being passed to the rectum,

Rectum and Anus

• Rectum: Stores waste.
• Anus: Where defecation (the expulsion of waste) happens.

Lower GI System Conditions

• Constipation: Characterized by hardened fecal material and difficulty passing stools.
• Diarrhea: Loose, watery stool.
• Inflammatory Bowel Disease: Inflammation of the bowel, including conditions like Crohn's disease and ulcerative colitis.

Lower GI Medications

• Include antidiarrheals, anti-flatulents, laxatives, and aminosalicylates.

Diarrhea Defined

• Having 3 or more loose or liquid bowel movements within 24 hours.
• Stools can be more frequent than what is considered normal for that person.

Antidiarrheals

• Used to treat acute or chronic diarrhea, including cases associated with IBD.
• Some anti-diarrheal drugs are opioid-related that have sedative and euphoric effects but lack analgesic activity.

Antidiarrheal Medications Names

• Contains bimatrol (Pepto)
• Composed of bismuth subsalicylate (Pepto-Bismol)
• Includes diphenoxylate (Lomotil)
• Has loperamide (Imodium)

Bismuth Subsalicylate (Pepto-Bismol)

• A subsalicylate gastroprotective medication with anti-inflammatory and anti-secretory properties.
• Functions as an antacid to decrease stomach acid.
• As an antimicrobial, it coats and kills bacteria causing diarrhea and prevents them from releasing toxins.
• Diminishes inflammation of the intestines.
• Absorbs toxins and decrease intestinal secretions.
• It absorbs excess fluid and provide protective effects to the mucosal lining of the intestines which acts as an antidiarrheal

Antidiarrheals: Contraindications

• Do not give Pepto to children under 2 years old.
• Use TUMS Calcium carbonate which is the children’s Pepto and can cause a constipating effect.

Loperamide (Imodium)

• Antidiarrheal/Opioid Combination Med that's an opioid agonist.
• This medication works on mu-opioid receptors in intestinal smooth muscle.
• It helps slow down intestinal motility.
• It reduces the frequency and urgency of diarrhea.
• Its use allows more time for fluid to be absorbed in the colon, forming firmer stools.
• It helps increase electrolyte and water absorption.

Diphenoxylate/Atropine (Lomotil)

• In the antidiarrheal/opioid class
• Contains a synthetic opioid that works similarly to loperamide.
• This medication works through binding to mu-opioid receptors in the gut.
• Diphenoxylate binds to opioid receptors that control peristalsis and motility, slowing down intestinal motility.
• Allowing the intestines more time to absorb water and electrolytes and forming firmer stools.
• It contains atropine to discourage abuse, as it causes unpleasant side effects (dry mouth, tachycardia) if taken in large amounts.

Antidiarrheals: Adverse Reactions

• Gastrointestinal Reactions: Anorexia, nausea, vomiting, constipation, also abdominal discomfort, pain, distention
• Other reactions can be dizziness, drowsiness, headache, sedation and euphoria or rash.

Constipation

• Abnormally infrequent and difficult passage of feces through the lower GI tract as it develops
• It's a symptom, not a disease.
• It can be a disorder of movement through the colon and/or rectum, caused by a variety of diseases or drugs.

Laxatives

• They relieve constipation.

Bulk-Forming Laxatives

• Laxatives with high fiber.
• Absorbs water to increase bulk in the stool.
• Distends the bowel to initiate reflex bowel activity.
• Examples: psyllium (Metamucil), methylcellulose (Citrucel), and Polycarbophil (FiberCon).

Bulk Forming Medications Side effects

• Has side effects of bloating, flatulence (gas)
• Abdominal discomfort in some patients.
• Rare allergic reactions e.g., rash

Bulk Forming Medications: Nursing Considerations

• Ensure the patient drinks plenty of fluids when using bulk-forming agents to avoid dehydration or intestinal blockage.
• Caution in patients with intestinal obstructions.
• Teach patients to take the medication with adequate fluid to prevent choking or blockage.

Emollient Laxatives

• Stool softeners and lubricants
• Promote more water and fat in the stools: Coats the stool and the intestinal lining to prevent water from being absorbed, which softens the stool and makes it easier to pass.
• Lubricate fecal material and intestinal walls.
• Examples of stool softeners include docusate salts (Colace, Surfak) and mineral oil as lubricants.

Laxatives (other forms)

• Hyperosmotics: glycerin supp, Lactulose and Polyethylene Glycol
• Stimulants of parastalsis; sennosides , senna (Senokot), bisacodyl (Ducolax) and Castor oil

Hyperosmotic Laxatives: Mechanism

• These include polyethylene glycol (GoLYTELY), sorbitol, glycerin, lactulose (Chronulac).
• They increase fecal water content.
• Resulting in bowel distention, increased peristalsis, and evacuation

Saline Laxatives: Mechanism

• Examples: magnesium sulfate (Epsom salts), magnesium hydroxide (MOM), magnesium citrate, sodium phosphate (Fleet Phospho-Soda, Fleet enema).
• Increase osmotic pressure in the intestinal tract causing more water to enter the intestines.
• Resulting in bowel distention, increased peristalsis, and evacuation.

Stimulant Laxatives: Mechanism

• Examples include castor oil (Granulex), senna (Senokot), cascara.
• Increase persitalsis via intestinal nerve stimulation

Laxatives: General Adverse Reactions

• Can cause constipation or diarrhea
• Resulting in abdominal pain or discomfort
• In some cases can cause nausea and vomiting
• Also includes perianal irritation, fainting, bloating, flatulence and/or weakness

Laxatives: Side Effects

• Bulk forming: Impaction, obstruction of esophagus, stomach, small intestine, and colon; fluid overload.
• Emollient: Skin rashes, decreased absorption of vitamins.
• Hyperosmotic: Abdominal bloating, rectal irritation.

Laxatives: Side Effects (Cont'd)

• Saline: Magnesium toxicity (with renal insufficiency), cramping, diarrhea, increased thirst.
• Stimulant: Nutrient malabsorption, skin rashes, gastric irritation, rectal irritation.

Laxatives: Side Effects (Cont'd)

• All laxatives can cause electrolyte imbalances

Laxatives: Nursing Implications

• A healthy, high-fiber diet and increased fluid intake should be encouraged as an alternative to laxative use
• Long-term use of laxatives can lead to dependency as they often result in decreased bowel tone
• All laxative tablets should be swallowed whole, not crushed or chewed, especially if enteric coated
• Patients need to take all laxative tablets with 6 to 8 ounces of water
• And patients should take bulk-forming laxatives as directed by the manufacturer with at least 240 mL (8 ounces) of water

Laxatives: Nursing Concerns

• Has a risk for Imbalanced Fluid Volume r/t diarrhea

Irritable Bowel Syndrome (IBS)

• A functional bowel disorder that affects 15% of the population.
• Is characteristic by a cluster of symptoms in the absence of detectable structural abnormalities
• Includes a diverse pathophysiology associated with abnormalities in GI tract motility (either diarrhea or constipation).
• Research has studied the role of serotonin in IBS
• Many of the drugs used for Rx of IBS act by serotonergic mechanisms

Crohn's Disease and Ulcerative Colitis

• Are conditions that cause inflammation in the digestive tract, leading to symptoms such as diarrhea, abdominal pain, and cramping.

Aminosalicylates

• These are 5-ASA (5-aminosalicylic acid) medications.
• Aspirin-like compounds with anti-inflammatory action
• Used to treat Crohn’s disease and ulcerative colitis, which are inflammatory diseases.
• Examples include Mesalamine, Sulfasalazine, Olsalazine, and balsalazide.

Aminosalicylates: Adverse Reactions

• GI system reactions: abdominal pain, nausea, diarrhea
• Include headache, dizziness, fever and weakness
• Some allergic reactions can be rash.

Mesalamine (5-ASA)

• This medication is an anti-inflammatory that works by inhibiting the production of certain chemicals in the body (prostaglandins and leukotrienes) that cause inflammation
• It specifically targets the lining of the gastrointestinal tract, where inflammation is occurring
• Treats ulcerative colitis and sometimes Crohn's disease, to reduce inflammation in the colon and rectum
• Can cause side effects of headache, nausea, abdominal pain, diarrhea, plus more serious effects like kidney problems or rash.
• Encourage hydration when taking the medication