Small intestine
It is approximately 1.5 cm in diameter in newborns after 35 weeks of gestational age, and 2.5–3 cm (1 inch) in diameter in adults. On abdominal X-rays, the small intestine is considered to be abnormally dilated when the diameter exceeds 3 cm. On CT scans, a diameter of over 2.5 cm is considered abnormally dilated. The surface area of the human small intestinal mucosa, due to enlargement caused by folds, villi and microvilli, averages 30 square meters.
Esophagitis
Esophagitis can be asymptomatic; or can cause epigastric and/or substernal burning pain, especially when lying down or straining; and can make swallowing difficult (dysphagia). The most common cause of esophagitis is the reverse flow of acid from the stomach into the lower esophagus: gastroesophageal reflux disease (GERD). 
The esophagus is a muscular tube made of both voluntary and involuntary muscles. It is responsible for peristalsis of food. It is about 8 inches long and passes through the diaphragm before entering the stomach. The esophagus is made up of four layers: from the inside out, they are the mucosa, submucosa, muscularis externa, and the serosa. The mucosa, the inner most layer and lining of the esophagus, is composed of stratified squamous epithelium, lamina propria, and muscularis mucosae. At the end of the esophagus is the lower esophageal sphincter, which normally prevents stomach acid from enteringthe esophagus.