GI System Anatomy and Physiology

Anatomy and Physiology Review

  • Will not be asked about diseases directly, but understanding anatomy and physiology is important for medication and overall understanding.

Location of Liver

  • The liver is located in the upper right quadrant.
  • It's crucial to know the location of organs, and it's considered unacceptable for graduating students not to know basic anatomy.

Gastrointestinal (GI) Anatomy

  • Mouth:
    • The start of the digestive system.
  • Esophagus:
    • A tube behind the windpipe (trachea) that leads to the stomach.
  • Stomach:
    • Receives food from the esophagus.
  • Small Intestine:
    • Composed of several parts, including the duodenum.
  • Large Intestine (Colon):
    • Follows the small intestine.

Detailed Breakdown of GI Tract

  • Mouth to Esophagus:
    • Food passes from the mouth, through the esophagus, to the stomach.
  • Stomach to Intestines:
    • From the stomach, food moves to the duodenum, then through the small intestine, and finally into the large colon.
  • Large Colon:
    • Ascending, transverse, descending, sigmoid, and rectum.

Mouth Anatomy

  • Tongue:
    • Important organ with taste buds.
  • Saliva:
    • Contains antimicrobial substances and starts the digestion process in the mouth.
  • Uvula:
    • A small structure in the back of the mouth that blocks the passage to the nasal cavity during swallowing.
  • Epiglottis:
    • A protective mechanism that closes the trachea during swallowing, preventing food from entering the airway.
    • Bending the head forward can aid swallowing by naturally closing the trachea.

Nasogastric Tube Insertion

  • Nasogastric Tube:
    • Inserted through the nose and goes to the stomach.
    • A potential complication is the tube entering the trachea instead of the esophagus.
    • In rare cases, the tube can go to the brain, causing severe neurological damage.
    • The goal is to ensure the tube goes down the esophagus.
  • Esophagus as a Passageway:
    • The esophagus transports food to the stomach in a few seconds (liquids) to up to 20 seconds (solids).

Stomach Anatomy and Function

  • Lower Esophageal Sphincter (LES):
    • A sphincter that opens and closes to control the passage of food from the esophagus to the stomach.
  • Pyloric Sphincter:
    • Controls the passage of food from the stomach to the duodenum.
  • Stomach Capacity and Function:
    • The stomach stores and churns food, gradually releasing it into the duodenum.
    • The stomach can rupture if excessively full.
  • Chyme:
    • Food is churned into chyme before being released into the duodenum.
  • Sphincter Failure:
    • If the LES fails, stomach contents can reflux into the esophagus.

Stomach Acid

  • Hydrochloric Acid:
    • The stomach contains hydrochloric acid with a low pH (1.5-3.5) to break down food and kill bacteria.
    • The stomach’s acidity helps digest food and protect against bacterial infections.
  • Stomach Lining:
    • The stomach has three layers (unlike the rest of the GI system, which has two) to protect itself from the acid.
  • Ulcers:
    • Can occur if the stomach's protective mechanisms fail.
  • Heartburn:
    • Occurs when stomach acid refluxes into the esophagus.
    • Esophagus lacks the protective layers of the stomach and gets burned by the acid.
  • Myocardial Infarction in Females:
    • Can sometimes present as GI problems.
  • Ovarian Cancer:
    • Can present as GI problems such as indigestion, flatulence, constipation, or diarrhea.
  • Barrett's Esophagus:
    • Chronic acid exposure can cause scarring and constriction of the esophagus.
  • Ulcer Pain:
    • Pain with or before food indicates a stomach ulcer.
    • Pain 2-3 hours after eating indicates a duodenal ulcer.

NSAIDs and Ulcers

  • NSAIDs (e.g., Aleve, ibuprofen):
    • Can cause ulcers by inhibiting prostaglandins, which protect the stomach lining.
    • NSAIDs inhibit prostaglandins at the site of injury, reducing pain signals to the brain.
    • Prostaglandins in the stomach help protect the stomach lining from acid.
  • Administration:
    • NSAIDs are often given with food to mitigate ulcer risk.
  • Alternative Pain Relief:
    • Acetaminophen (Tylenol) is a substitute for those who cannot tolerate NSAIDs.

Parietal Cells and Vitamin B12

  • Parietal Cells:
    • Located in the stomach and produce intrinsic factor, which is necessary for vitamin B12 absorption.
  • B12 Deficiency:
    • Parietal cell dysfunction can lead to B12 deficiency and anemia.
    • B12 injections are administered because oral B12 supplements are not absorbed without intrinsic factor.

H. Pylori

  • H. Pylori:
    • A bacterium that lives in the pyloric region of the stomach and increases the risk of ulcers.
  • H. Pylori Detection:
    • Detected via a breath test that measures carbon dioxide levels after ingesting urea.
    • H. Pylori converts urea into ammonia and carbon dioxide.
  • Symptoms:
    • Excessive burping with a possibly distinct smell may indicate H. Pylori infection.

Small Intestine

  • Duodenum Length:
    • Approximately 12 finger-widths long.
  • Tubes:
    • Gastric tubes are inserted directly into the stomach.
    • Jejunum tubes are inserted into the jejunum, often for patients with stomach cancer.
  • Function:
    • Digestion and nutrient absorption occur in the small intestine, which has a unique structure to facilitate this process.

Large Intestine (Colon)

  • Function:
    • The primary function is to absorb fluids, turning liquid stool into solid stool.
  • Colostomy:
    • A surgical opening where the colon is diverted, and stool exits into a bag.
    • The consistency and odor of the stool depend on the location of the colostomy.
    • Colostomies closer to the rectum produce more solid stool with less odor.
  • Enteric Nervous System:
    • A special nervous system in the colon that operates somewhat independently.
    • Hirschsprung's disease occurs when a portion of the colon lacks nerve cells, leading to obstruction and requiring surgery.

Oral Conditions

Cold Sores

  • Herpes Simplex Virus:
    • Chronic, contagious, and requires contact precautions.
    • Often appear during immune system compromise or dehydration.
  • Treatment:
    • Antiviral creams (e.g., acyclovir) can diminish outbreaks if applied early.

Oral Candida (Thrush)

  • Fungal Infection:
    • Common in babies and immunocompromised individuals.
  • Identification:
    • If white patches can be wiped away with gauze, it is likely milk residue.
    • If it cannot be wiped away, it is likely candida.
  • Dentures:
    • Poor denture care can lead to candida.
    • Cleaning dentures with a toothbrush can create micro-cracks that harbor bacteria.

Canker Sores

  • Non-Contagious:
    • Painful sores with unknown causes, possibly stress-related.

Plaque and Calculus

  • Plaque:
    • Soft film of bacteria, saliva, and food that forms on teeth.
  • Calculus (Tartar):
    • Hardened plaque that forms within 48 hours.
    • Requires professional dental cleaning.

Xerostomia

  • Definition:
    • Dry mouth due to lack of saliva (hyposalivation)
  • Consequences:
    • Poor food chewing/digestion.
    • Reduced digestive enzymes and antibacterial properties.
  • Halitosis:
    • Bad breath.
    • Can indicate internal GI problems or poor oral hygiene.
    • Tongue appearance can provide insights into GI health and hydration.

Oral Care

  • Xerostomia:
    • Not contagious and caused by lack of saliva.
  • Commercial Mouthwash:
    • Often contains alcohol, which can be irritating.
  • Magic Mouthwash:
    • A special mouthwash for mucositis.
  • Toothbrush:
    • Use a soft-bristled toothbrush.
  • Hard Candy:
    • Avoid sucking on hard candy as it can cause trauma.
  • Viscous Lidocaine:
    • A soothing anesthetic.
  • Infant Oral Care:
    • Use a soft cloth to clean gums even before teeth erupt.
    • First dental visit should be within the first year.
  • Oral Candidiasis Treatment:
    • Nystatin mouthwash.
  • Steroids:
    • Can predispose individuals to oral candidiasis.
  • Mouthwash Recommendation:
    • Alcohol-free mouthwash to prevent dryness and irritation.
  • Bleeding Precautions:
    • Avoid flossing if platelets are low.
  • Oral Bacteria and Systemic Health:
    • Bacteria in the mouth can travel to the heart, causing infective endocarditis.
    • Poor oral hygiene can lead to bacteria traveling from the mouth to the throat and then to the heart.
    • Individuals with heart conditions or artificial valves are particularly vulnerable.

Gastroesophageal Reflux Disease (GERD) and Peptic Ulcer Disease (PUD)

  • GERD:
    • Occurs when the lower esophageal sphincter fails, allowing stomach contents to reflux into the esophagus (heartburn).
  • PUD:
    • Ulcers or wounds in the stomach or duodenum.
    • Can cause pain intensified by acid or food, bleeding, and in severe cases, perforation (a hole), which is an emergency requiring surgery.

Managing GERD and PUD

  • Limit NSAID Use:
    • Avoid ibuprofen and naproxen.
  • H. Pylori Treatment:
    • If present, requires antibiotics.

Medications for Acid-Related Conditions

  • Antacids:
    • Neutralize stomach acid quickly but provide short-term relief.
  • H2 Blockers:
    • Reduce stomach acid production.
  • PPIs (Proton Pump Inhibitors):
    • Potent inhibitors of stomach acid production.
  • Mucosal Protectants:
    • Protect the stomach lining.
  • Gastritis:
    • Inflammation of the stomach.
  • Perforated Ulcer:
    • An emergency condition where a hole forms in the stomach, allowing contents to leak into the abdominal cavity.

Antacids

  • Examples:
    • Sodium bicarbonate
    • Calcium carbonate (Tums)
    • Aluminum hydroxide
    • Magnesium hydroxide (Milk of Magnesia)
  • Mechanism:
    • Neutralize stomach acid by acting as a base to counteract acid.
  • Action:
    • Fast-acting with short-term effects.
  • Contraindications:
    • Heart failure (due to sodium content).
  • Side Effects:
    • Calcium and aluminum can cause constipation.
    • Magnesium can cause diarrhea.
    • Combination products are used to balance these effects.

Patient Teaching for Gastritis and Ulcers

  • Avoid Overeating:
    • Eat smaller, more frequent meals.
  • Manage Stress:
    • Stress can exacerbate ulcers.
  • Quit Smoking:
    • Smoking increases ulcer risk.
  • Avoid NSAIDs:
    • Use acetaminophen instead.

H2 Blockers

  • Examples:
    • Famotidine (Pepcid)
    • Cimetidine
    • Ranitidine ranitidine was removed from market due to cancer link.
  • Mechanism:
    • Reduce the amount of stomach acid produced.
  • Administration:
    • Given before meals.
  • Difference from Antacids:
    • Antacids neutralize acid, while H2 blockers reduce acid production.
  • Separate administration from other medications.

PPIs (Proton Pump Inhibitors)

  • Examples:
    • Omeprazole (Prilosec)
    • Pantoprazole (Protonix)
  • Administration:
    • Given before food.
  • Use:
    • Can be given intravenously for severe stomach pain.
    • Often used prophylactically in hospitalized patients to prevent stress ulcers.
  • Side Effects:
    • Long-term use can decrease calcium absorption, leading to osteoporosis.
    • Increased risk of C. difficile infection due to reduced stomach acid.

Sucralfate (Carafate)

  • Mechanism:
    • Forms a physical barrier over ulcers.
  • Administration:
    • Taken as a pill mixed with water before meals on an empty stomach and do not mix it with other medications.
  • Use:
    • Treats and prevents gastric ulcers by physically covering rough surfaces.

Misoprostol

  • Prostaglandin Analog:
    • Protects the stomach by increasing mucus production.
  • Use:
    • Used to protect the stomach in patients taking NSAIDs.
  • Contraindications:
    • Contraindicated in pregnancy due to its abortifacient effects (causes uterine contractions).
  • Side Effects:
    • Can cause dysmenorrhea (painful menstruation).

Treatment Decision Making Review

  • Antacids buffer and neutralize acid directly, are fast-acting, short-term, and have side effects like constipation or diarrhea.

Anti-Flatulence/Anticholinergics/Antacids

  • The patient requires an antacid to neutralize the acid.

H2 Blockers Review

  • Reduces acid in stomach.

PPI Review

  • Potent stomach acid reduction.

Methylchlorperamide

  • Enhances GI motility. Food proceeds faster.