Before a cell can reproduce, it must first replicate, or make a copy of, its DNA. Where DNA replication occurs depends upon whether the cells is a prokaryote or a eukaryote (see the RNA sidebar on the previous page for more about the types of cells). DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes.
Esophagogastroduodenoscopy (EGD) is a diagnostic procedure that allows the physician to diagnose and treat problems in the upper gastrointestinal (UGI) tract. The doctor uses a long, flexible, lighted tube called an endoscope. The endoscope is guided through the patient's mouth and throat, then through the esophagus, stomach, and duodenum (first part of the small intestine). The doctor can examine the inside of these organs and detect abnormalities.
You might hear your doctor or other medical staff refer to upper endoscopy as upper GI endoscopy, esophagogastroduodenoscopy (EGD) or panendoscopy. Why is upper endoscopy done? Upper endoscopy helps your doctor evaluate symptoms of persistent upper abdominal pain, nausea, vomiting or difficulty swallowing. It's the best test for finding the cause of bleeding from the upper gastrointestinal tract. It's also more accurate than X-ray films for detecting inflammation, ulcers and tumors of the esophagus, stomach and duodenum. Your doctor might use upper endoscopy to obtain a biopsy (small tissue samples).