Gastrointestinal System Foundations

The gastrointestinal tract digests food, absorbs fluid and nutrients, maintains a mucosal barrier, and moves contents forward. The liver processes absorbed substances and produces bile and clotting proteins; the pancreas contributes digestive enzymes and endocrine hormones. When one part fails, the bedside picture often reflects more than one problem: vomiting can cause volume depletion, inflammation can produce ileus, and liver dysfunction can alter both coagulation and mental status. Several physiologic patterns help determine urgency: - Bleeding removes circulating volume and may reduce oxygen delivery. Hematemesis, coffee-ground emesis, melena, hematochezia, pallor, tachycardia, dizziness, and falling urine output must be interpreted alongside blood pressure and mental status. - Inflammation or infection produces pain, fever, leukocytosis, tachycardia, and sometimes sepsis. A patient with a localized inflammatory process may deteriorate when perforation or bacterial translocation occurs. - Obstruction or impaired motility causes distension, cramping, vomiting, inability to pass stool or flatus, and fluid shifting into the bowel. The fluid is no longer available to support circulation, so obstruction can become a perfusion problem. - Malabsorption or excessive intestinal loss causes diarrhea, weight loss, anemia,...