NCLEX Review Guide: Gastrointestinal System & Nutrition

GI Tract Structure and Function

• The alimentary canal consists of mouth, esophagus, stomach, small intestine, and large intestine, working together to digest food and absorb nutrients. Each segment has specialized functions and anatomical features that facilitate optimal digestion and absorption.
• The small intestine is the primary site of nutrient absorption with three sections: duodenum (iron and calcium absorption), jejunum (carbohydrates and proteins), and ileum (vitamin B12 and bile salts). Understanding these specific absorption sites is crucial for recognizing deficiency patterns in various GI disorders.
• Peristalsis is the coordinated muscular contractions that propel food through the digestive tract, regulated by the enteric nervous system and influenced by parasympathetic stimulation. Disruption of peristalsis can lead to conditions like paralytic ileus or gastroparesis.

Key Digestive Hormones

• Gastrin is released by G-cells in the stomach antrum in response to protein ingestion, stimulating gastric acid secretion and gastric motility. Elevated gastrin levels can indicate Zollinger-Ellison syndrome or gastrinoma.
• Cholecystokinin (CCK) is secreted by the duodenum when fats and proteins enter, causing gallbladder contraction and pancreatic enzyme release. CCK also promotes satiety by slowing gastric emptying and stimulating the vagus nerve.
• Secretin is released by duodenal S-cells in response to acidic chyme, stimulating pancreatic bicarbonate secretion to neutralize stomach acid. This hormone also inhibits gastric acid production through negative feedback.

Macronutrients and Energy Metabolism

• Carbohydrates provide 4 kcal/gram and should comprise 45-65% of total daily calories, with emphasis on complex carbohydrates for sustained energy release. Simple sugars cause rapid blood glucose spikes, while fiber promotes satiety and digestive health.
• Proteins provide 4 kcal/gram and require 0.8-1.2 g/kg body weight daily for healthy adults, with higher needs during illness, wound healing, or growth periods. Complete proteins contain all essential amino acids, while incomplete proteins lack one or more essential amino acids.
• Lipids provide 9 kcal/gram and should comprise 20-35% of total calories, with emphasis on unsaturated fats and omega-3 fatty acids for cardiovascular health. Essential fatty acids cannot be synthesized by the body and must be obtained through diet.

Peptic Ulcer Disease and GERD

• Peptic ulcers are primarily caused by H. pylori infection (70%) or NSAIDs, not stress or spicy foods as commonly believed. Triple therapy includes two antibiotics plus a proton pump inhibitor for H. pylori eradication.
• GERD results from lower esophageal sphincter dysfunction, allowing gastric acid reflux into the esophagus, potentially leading to Barrett's esophagus and increased cancer risk. Lifestyle modifications include elevating head of bed, avoiding trigger foods, and eating smaller, frequent meals.

1. Assess pain characteristics: burning, gnawing, or aching
2. Monitor for complications: bleeding, perforation, obstruction
3. Administer medications as ordered: PPIs, H2 blockers, antibiotics
4. Educate on dietary modifications and lifestyle changes
5. Schedule follow-up endoscopy to confirm healing

Essential Study Strategies

• Create concept maps linking GI anatomy to common disorders and their manifestations
• Practice calculating nutritional requirements for different patient populations
• Memorize normal lab values: albumin (3.5-5.0 g/dL), total protein (6.0-8.0 g/dL)