Understanding the Digestive Tract and Accessory Glands

The Digestive System

The digestive system transforms food into nutrients that are the right size to reach body cells and be absorbed. To carry out this function, the digestive system consists of a group of organs and structures: the digestive tract and the accessory glands.

The Digestive Tract

The digestive tract, in order from top to bottom, includes:

• Mouth: The entry point of the digestive tract. It contains:
  • Teeth to bite and break food into small pieces.
  • A tongue to mix and swallow food, and enable the sense of taste.
  • Salivary glands.
• Pharynx: A cavity shared by the digestive and respiratory systems. Food passes towards the esophagus. The epiglottis, a small, flexible cartilage, prevents food from reaching the respiratory tract.
• Esophagus: A tube with a length of 25cm that extends down the thorax, across the diaphragm, and into the stomach. It connects the pharynx with the stomach.
• Stomach: A wide part of the digestive tract found in the abdominal cavity. Its internal walls have glands that secrete gastric juices. Two valves regulate the flow of food: the cardia at the entry point, and the pylorus at the exit point.
• Small Intestine: A tube with a length of about 6m in the abdominal cavity. It has many folds with glands that secrete intestinal juice and is divided into three segments: duodenum, jejunum, and ileum.
• Large Intestine: The last part of the digestive tract, with a length of 1.5m, which surrounds the small intestine. It is divided into three parts: cecum, colon, and rectum. The vermiform appendix is a tube connected to the cecum. The colon is divided into three parts: ascending, transverse, and descending. The rectum terminates into the anus.

The Accessory Glands

These accessory glands produce digestive juice and secrete it into the tract.

• Salivary Glands: They produce and secrete saliva into the mouth. The three main parts are: sublingual (located under the tongue), submandibular (located in the jaw), and parotids (located close to the ears).
• Pancreas: A long, flat organ located below the stomach that secretes pancreatic juice into the duodenum. It also produces substances involved in glucose metabolism, which are released directly into the bloodstream.
• Liver: The largest accessory gland, it has several functions:
  1. Synthesizes proteins.
  2. Regulates glucose metabolism.
  3. Stores vitamins and minerals.
  4. Processes alcohol and drugs in the blood for elimination.
  5. Produces bile, which is stored in the gallbladder before being secreted into the duodenum. Bile contains bile salts that facilitate the digestion and absorption of lipids.