The patient presented with _____, severe upper abdominal pain that occurs when stomach acid damages the lining of the esophagus.

Heartburn, or pyrosis, is a burning sensation in the chest caused by gastric acid reflux into the esophagus. It's a primary symptom of gastroesophageal reflux disease (GERD). The pain typically worsens when lying down or bending over. The condition occurs when the lower esophageal sphincter relaxes inappropriately, allowing stomach contents to flow back into the esophagus.

• Heartburn (Pyrosis)
- Burning sensation in chest/upper abdomen
- Caused by stomach acid reflux
- Primary symptom of GERD
- Pain worsens when lying down/bending over
- Related to lower esophageal sphincter dysfunction

• GERD (Gastroesophageal Reflux Disease)
- Chronic digestive disorder
- Symptoms: heartburn, regurgitation, chest pain
- Risk factors: obesity, pregnancy, smoking
- Complications: esophagitis, Barrett's esophagus
- Treatment: lifestyle changes, antacids, PPIs

• Esophageal Anatomy
- Muscular tube connecting throat to stomach
- Lower esophageal sphincter (LES) controls food passage
- Lined with stratified squamous epithelium
- Normal pH: 7.0
- Length: approximately 25cm

• Gastric Acid
- Main component: hydrochloric acid (HCl)
- pH: 1.5-3.5
- Produced by parietal cells
- Functions: protein digestion, pathogen defense
- Regulated by hormones and nervous system