Inside the Digestive System Summary & Study Notes

🧭 Overview of the Gastrointestinal (GI) System

The GI tract includes the upper GI (mouth, salivary glands, esophagus, stomach) and the lower GI (small intestine, large intestine, rectum). Supporting organs include the liver, pancreas, and gallbladder. The GI system coordinates digestion, absorption, and elimination.

🦷 Oral Cavity and Esophagus — Key Concepts

The oral cavity contains structures essential for intake: oropharynx, hard/soft palate, gums, teeth, tongue, and buccal mucosa. Salivary glands aid chewing and swallowing. The epiglottis protects the airway during swallowing. The esophagus uses sphincters and vagal afferents to move food; lower esophageal sphincter (LES) dysfunction contributes to reflux.

😷 Common Oral Disorders

Oral herpes (cold sores) and aphthous ulcers (canker sores) cause pain and limit intake. Oral candidiasis (thrush) appears as cheesy white patches that do not wipe off. Periodontitis can lead to tooth loss and is linked to systemic disease, including increased coronary artery disease risk. Oral cancer is a significant portion of head and neck cancers and may present with pain or burning.

🔍 Nursing Assessment — Oral & Esophageal

Inspect color, texture, and integrity of oral structures. Note odor, bleeding, and condition of dentures or orthodontic devices. Palpate local lymph nodes, obtain vital signs, review medications and past history, and evaluate swallowing and absorption risks.

🔁 Gastroesophageal Reflux Disease (GERD)

GERD involves acid reflux that erodes esophageal lining and can cause Barrett’s esophagus with chronic inflammation. Psychological stress can exacerbate symptoms. Chronic GERD increases risk of strictures and esophageal adenocarcinoma.

Role of the nurse: identify comorbidities (e.g., hiatal hernia, pregnancy, connective tissue disorders), assess lifestyle factors (alcohol, caffeine, smoking), and teach symptom management.

🫁 Hiatal Hernia

Commonly causes heartburn and sour taste after eating and may contribute to GERD. Diagnostic tools include EGD (esophagogastroduodenoscopy) and pH monitoring.

🩺 Peptic Ulcer Disease (PUD)

PUD are open sores in the stomach or duodenal lining. Risk factors: H. pylori infection, long-term NSAID use, alcohol, smoking, high-fat diet, age >60, and certain comorbidities (e.g., Crohn’s, Type O blood). Symptoms include burning or gnawing abdominal pain, nausea, bloating, early satiety, and possible GI bleeding.

Diagnostics: stool occult blood, CBC, electrolytes, LFTs, amylase/lipase, urea breath test or stool antigen for H. pylori, and upper GI endoscopy.

Treatment principles: dietary modifications (avoid acidic, spicy foods, caffeine, alcohol), stress reduction, and medications such as PPIs (watch for hypocalcemia, hypomagnesemia, osteoporosis, and $B_{12}$ deficiency). Sucralfate should be taken on an empty stomach (do not crush).

🍽️ Stomach and Duodenum

The stomach stores chyme and secretes digestive juices; the pyloric sphincter regulates passage into the duodenum. The pancreas secretes enzymes (amylase, lipase) into the duodenum to neutralize acid and digest nutrients.

⚠️ Peritonitis

Peritonitis is infection of the peritoneum, often from a ruptured bowel. It presents with a rigid, board-like abdomen and is a surgical emergency. Management includes urgent operative intervention, NG decompression, and patient positioning (Fowler’s or semi-Fowler’s).

🧬 Liver Disease and Nursing Role

Liver disease ranges from fatty liver (ALD, NAFLD/NASH) to viral hepatitis and cirrhosis. Nurses should monitor liver enzymes, assess for jaundice (sclera, palate), abdominal pain and radiation, palmar erythema, caput medusae, spider angiomas, and ascites. Educate on alcohol avoidance, low-fat diets, and infection control for contagious hepatitis.

🧪 Hepatitis Types — Brief Summary

• HAV: fecal-oral spread; often self-limiting.
• HBV: blood-borne; vaccine available; chronic infection possible.
• HCV: blood-borne; curable in most cases with modern therapy; no vaccine.
• HDV: requires HBV co-infection; prevented by HBV vaccine.
• HEV: fecal-oral; can be self-limiting or chronic. Also consider bacterial, chemical/alcoholic, and steatohepatitis causes.

⚒️ Cirrhosis and Liver Regeneration

Cirrhosis is scarring from chronic liver injury (alcohol, viral hepatitis, NAFLD). The liver can regenerate to an extent, but cirrhosis represents permanent scarring and impaired function. Chronic inflammation increases risk of hepatocellular carcinoma.

📈 Liver Function Tests (LFTs) — Key Values

• AST: normal approx. 10–40 U/L (men), 9–32 U/L (women).
• ALT: liver-specific enzyme; normal approx. 29–33 IU/L (men), 19–25 IU/L (women).
• ALP: 44–147 IU/L (liver and bone source).
• Bilirubin: ≤ 1.2 mg/dL normal.
• Ammonia ($NH_4$): normal 15–45 ng/dL. Elevated $NH_4$ indicates advanced liver dysfunction and risk for hepatic encephalopathy.
• INR: prolonged when liver synthetic function is impaired.

Clinical implications: rising $NH_4$ can cause confusion, altered mental status, and ammonia breath odor. Management may include antibiotics and protein-restricted diets to reduce ammonia production.

🩺 Pancreas — Pancreatitis

Acute pancreatitis presents with severe, sudden abdominal pain and release of trypsin and other enzymes. Causes: alcohol, smoking, drug-induced, autoimmune, gallstones, trauma, infection, hypertriglyceridemia, hypercalcemia, family history, or idiopathic. Labs: amylase (norm 23–85 U/L) and lipase (norm 0–160 U/L). Imaging: ultrasound, CT. Recurrent pancreatitis increases risk for pancreatic cancer. Surgical option: Whipple (pancreatoduodenectomy) for malignancy.

🧾 Lower GI — Anatomy & Function

The small intestine (including jejunum and ileum) absorbs nutrients (sugars, amino acids, fatty acids, and $B_{12}$ in the ileum). The large intestine/colon absorbs water and electrolytes, houses bacterial flora that synthesize vitamins (niacin, vitamin B1, and vitamin K), and forms stool. The rectum stores feces until defecation.

💩 GI Bleeding — Clinical Clues

Upper GI bleeding may present as coffee-ground emesis and dark, tarry stools. Lower GI bleeding varies: tarry stools or bright red blood depending on transit speed. Occult stool testing detects small, otherwise unnoticed bleeding. Certain foods (horseradish, mustard) and iron supplements can cause false positives or dark stools.

🩹 Ostomies and Nutritional Consequences

Ostomies may be required for obstruction, post-op bowel rest, or short bowel syndrome. Patients can experience dehydration, electrolyte imbalances, vitamin and mineral deficiencies, malabsorption, and anemia from chronic blood loss.

🔥 Inflammatory Lower GI Conditions

• Crohn’s disease: can affect any GI segment and full-thickness bowel wall with patchy "cobblestoning." Symptoms include diarrhea, rectal bleeding, abscesses, fistulas, skin lesions, and joint pain.
• Ulcerative colitis: affects the colonic mucosa (continuous lesions) with urgency, increased bowel movements, mucous or bloody stools, nocturnal symptoms, and abdominal pain. Both are inflammatory bowel diseases (IBD) with differing patterns of involvement and complications.

🚫 Bowel Obstruction — Small vs Large Bowel

Small bowel obstruction: sporadic pain, visible peristaltic waves, projectile vomiting, possible fecal-like emesis. Large bowel obstruction: constant pain, marked abdominal distention, less frequent vomiting, possible stool leaking around impaction. Common signs for both: hyperactive bowel sounds above the obstruction and hypoactive below; inability to pass stool or flatus for ≥8 hours is concerning.

📌 Other Lower GI Disorders

• Diverticulitis: inflamed diverticula (often LLQ pain), fever, nausea. Complications include abscess, obstruction, fistula, or peritonitis. Avoid opiates that worsen constipation.
• IBS (Irritable Bowel Syndrome): a functional disorder with cramping, bloating, and variable bowel habits. Triggers include caffeine and artificial sweeteners.
• Celiac disease (gluten enteropathy): autoimmune intolerance to gluten causing diarrhea, weight loss, anemia, bloating, and malabsorption leading to bone loss, neuropathy, and other systemic effects. Diagnosis: antigliadin antibody testing and small bowel biopsy. Common gluten sources: wheat, barley, rye, malt (and many processed foods).

🧾 Practical Nursing Tips

• Inspect oral cavity and swallowing ability; coordinate dental care and mucosal hygiene for oncology patients.
• Monitor LFTs, INR, electrolytes, and $NH_4$ in liver disease; provide safety for patients with encephalopathy.
• Teach PPI risks (bone and mineral effects) and adherence to ulcer and GERD regimens.
• Recognize peritonitis and bowel obstruction as surgical emergencies and initiate rapid escalation.
• Address nutrition, fluid status, and ostomy care to prevent dehydration and deficiencies.

✅ Quick Recall — High-Yield Points

• Chronic GERD → Barrett’s esophagus → ↑ risk of esophageal adenocarcinoma.
• H. pylori and NSAIDs are prime causes of PUD.
• Elevated $NH_4$ → hepatic encephalopathy; reduce gut bacteria and protein breakdown.
• Recurrent pancreatitis can precede pancreatic cancer; check amylase/lipase and image.
• Distinguish small vs large bowel obstruction by pain pattern, vomiting, and distention.
• Celiac disease requires gluten avoidance; confirm with serology and biopsy.

These notes summarize clinical anatomy, common disorders, diagnostics, and nursing priorities for alterations in digestion and bowel elimination. Use them as a concise reference for assessment and management planning.