Most of the gastrointestinal (G.I.) tract from the esophagus to the anus can be examined by endoscopy (endo, inside; scope, see; to see inside the body). Panendoscopy is a procedure that allows the physician to examine the lining of the upper part of the gastrointestinal tract (i.e. the esophagus, stomach and duodenum). This involves the passage of a tube by mouth through the esophagus into the stomach and duodenum. The tube is long and flexible and contains a light source, lens system for focusing and fiber optics. The fiber optics conduct light to within these organs and an image back to a video camera that is connected to a monitor. The tube also contains a channel through which small instruments can be passed for various different uses.

Anatomy and Physiology

• Esophagus, sometimes called the gullet, is a tube-like structure that connects the back of the throat, the pharynx, to the stomach (Figure 1) (See Esophagectomy)
  
  1. It is about 22 - 27 centimeters (9 to 11 inches) long and is composed mostly of muscle
     
  2. It serves as the passage for food and saliva to get from the mouth to the stomach.
     
  3. A few inches of the esophagus are in the neck (called the cervical esophagus)
     
  4. Most of the esophagus is located in the chest. It passes into the abdomen through the diaphragm, the broad muscular and fibrous structure that separates the chest from the abdominal cavity. Only an inch or so of the esophagus is located in the abdominal cavity where it attaches to the stomach
     
  5. The upper and lower ends of the esophagus are not wide open at all times, but rather have a mechanism that functions like a valve. These are called the upper and lower esophageal sphincters.
     
  6. The inner lining of the esophagus is made up of a tissue called epithelium. Most of the epithelium resembles skin in many respects and is of a cell type called squamous (flat) cell
     
• Stomach is a reverse C-shaped organ that lies under the left lower ribs and left upper part of the abdomen (Figure 1) (See Gastrectomy)
  
  1. Food entering the mouth is passed into the esophagus and then goes into the upper end of the stomach. The stomach holds and mixes the food with gastric juices that aid in digestion and then passes the mixture through the pylorus, a muscular sphincter or gate, that controls the passage of the stomach contents into the duodenum, which is the beginning of the small bowel
     
  2. Glands in the wall of the stomach produce the gastric juices. After three to four hours, food entering the stomach is reduced by these juices to a liquid and ready to enter the small bowel to continue digestion
     
  3. The stomach is divided into three parts (Figure 1):
     
  • The cardia is the part of the stomach that is adjacent to the esophagus
    
  • The body of the stomach is the largest part and has two curvatures, the lesser curvature, which lies on the inside of the C, and the greater curvature, which lies on the outside of the C
    
  • The pylorus is the part of the stomach that lies at the end of the stomach and is demarcated from the body by a difference in the type of glands from those in the body
    
  4. The stomach is mobile and changes shape depending on whether it is full or empty or whether the person is standing or lying down. It is relatively fixed at the cardia, the part of the stomach near the esophagus
     
• Duodenum connects the stomach to the jejunum (the second part of the small bowel) (Figure 1) (See Surgery of the Duodenum)
  
  1. It is 20 cm (8 inches) in length and divided into four parts
     
  2. The duodenum is retroperitoneal (has peritoneum, the thin layer of tissue that lines the abdominal cavity) only on the anterior (front) side; fixed in location; wraps around the head, neck and body of the pancreas; and the superior mesenteric artery and vein (major blood vessels for the bowel) pass anterior to the 3rd portion.
     
  3. The ampulla of Vater (entrance site into duodenum of joined common bile duct and pancreatic duct) enters the medial (towards the midline) side of the 2nd portion of the duodenum.
     
  4. The accessory pancreatic duct enters slightly higher in the medial wall of the duodenum
     
  5. The ligament of Treitz (a supporting band of peritoneum and muscle fibers) marks the point between the fourth part of the duodenum and jejunum
     
  6. The duodenum produces many hormones that help regulate digestion. Liver bile and pancreatic secretions are added to the bowel through the ampulla of Vater. The actual passage and presence of food in the duodenum triggers the flow of hormones, bile and pancreatic secretions. By the time food leaves the duodenum most of the ingredients necessary for digestion have been added. Little digestion and absorption (passage of nutrients from the bowel into the blood) take place in the duodenum

Figure 1 - Anatomy of the esophagus, stomach and duodenum. © N. Gordon