Accessory Organs of the Alimentary Canal

Digestive Organs Other than the intestines and the stomach, the following are also part of the digestive system: 

Teeth 

The role the teeth play in food processing needs little introduction; we masticate, or chew, by opening and closing our jaws and moving them from side to side while continuously using our tongue to move the food between our teeth. 

• Function. The teeth tear and grind the food, breaking it down into smaller fragments. 

• Deciduous teeth. The first set of teeth is the deciduous teeth, also called baby teeth or milk teeth, and they begin to erupt around 6 months, and a baby has a full set (20 teeth) by the age of 2 years. 

• Permanent teeth. As the second set of teeth, the deeper permanent teeth, enlarge and develop, the roots of the milk teeth are reabsorbed, and between the ages of 6 to 12 years they loosen and fall out.

• Incisors. The chisel-shaped incisors are adapted for cutting. 

• Canines. The fang like canines are for tearing and piercing. 

• Premolars and molars. Premolars (bicuspids) and molars have broad crowns with round cusps ( tips) and are best suited for grinding 

• Crown. The enamel-covered crown is the exposed part of the tooth above the gingiva or gum 

• Enamel. Enamel is the hardest substance in the body and is fairly brittle because it is heavily mineralized with calcium salts. 

• Root. The outer surface of the root is covered by a substance called cementum, which attaches the tooth to the periodontal membrane (ligament). 

• Dentin. Dentin, a bonelike material, underlies the enamel and forms the bulk of the tooth. 

• Pulp cavity. It surrounds a central pulp cavity, which contains a number of structures (connective tissue, blood vessels, and nerve fibers) collectively called the pulp. 

• Root canal. Where the pulp cavity extends into the root, it becomes the root canal, which provides a route for blood vessels, nerves, and other pulp structures to enter the pulp cavity of the tooth. 

Salivary Glands 

Three pairs of salivary glands empty their secretions into the mouth. 

• Parotid glands. The large parotid glands lie anterior to the ears and empty their secretions into the mouth. 

• Submandibular and sublingual glands. The submandibular and sublingual glands empty their secretions into the floor of the mouth through tiny ducts 

• Saliva. The product of the salivary glands, saliva, is a mixture of mucus and serous fluids. 

• Salivary amylase. The clear serous portion contains an enzyme, salivary amylase, in a bicarbonate-rich juice that begins the process of starch digestion in the mouth. Pancreas Only the pancreas produces enzymes that break down all categories of digestible foods. 

• Location. The pancreas is a soft, pink triangular gland that extends across the abdomen from the spleen to the duodenum; but most of the pancreas lies posterior to the parietal peritoneum, hence its location is referred to as retroperitoneal. 

• Pancreatic enzymes. The pancreatic enzymes are secreted into the duodenum in an alkaline fluid that neutralizes the acidic chyme coming in from the stomach. 

• Endocrine function. The pancreas also has an endocrine function; it produces hormones insulin and glucagon. Liver The liver is the largest gland in the body. 

• Location. Located under the diaphragm, more to the right side of the body, it overlies and almost completely covers the stomach. 

• Falciform ligament. The liver has four lobes and is suspended from the diaphragm and abdominal wall by a delicate mesentery cord, the falciform ligament. 

• Function. The liver’s digestive function is to produce bile. 

• Bile. Bile is a yellow-to-green, watery solution containing bile salts, bile pigments, cholesterol, phospholipids, and a variety of electrolytes. 

• Bile salts. Bile does not contain enzymes but its bile salts emulsify fats by physically breaking large fat globules into smaller ones, thus providing more surface area for the fat-digesting enzymes to work on. 

Gallbladder

While in the gallbladder, bile is concentrated by the removal of water. 

• Location. The gallbladder is a small, thin-walled green sac that snuggles in a shallow fossa in the inferior surface of the liver. 

• Cystic duct. When food digestion is not occurring, bile backs up the cystic duct and enters the gallbladder to be stored.