== Tongue ==

The tongue is divided anatomically into an anterior 2/3 or body, and a posterior 1/3 or root by a posteriorly oriented V-shaped groove, the sulcus terminalis. A pit, the foramen caecum, is located at the apex of the sulcus terminalis. It represents the embryonic point of origin of the thyroid gland.

== Salivary Glands ==

The salivary glands are divided into two main divisions. The intramural or minor salivary glands (labial, buccal, and palatine) lie within the submucosal connective tissue of the oral cavity. These intrinsic glands secrete continuously to moisten the oral cavity. Three pairs of extrinsic or major salivary glands, the parotid, the submandibular, and the sublingual, lie outside the walls of the oral cavity and must convey their secretions to the mouth by means of excretory ducts which pass through the mucosa. The major glands secrete intermittently in response to specific stimuli. The major salivary glands are classified as compound tubuloalveolar, exocrine glands. The secretory alveoli of the parotid glands are wholly serous, producing a watery secretion; those of the submandibular glands are mixed, although preponderantly serous, and those of the sublingual glands are mixed but preponderantly mucous.

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== Pancreas ==

The pancreas is both an exocrine and an endocrine gland. The exocrine pancreas is a compound tubuloacinar gland consisting of serous secretory cells arranged in acini. As a gland of external secretion, the serozymogenic products of the acini are conveyed to the lumen of the duodenum by means of a main excretory duct, the main pancreatic duct, and by an accessory pancreatic duct which in some individuals opens into the main duct before reaching the duodenum. The main duct extends the entire length of the gland receiving branches, interlobular ducts, from the individual lobules. Striated ducts are lacking in the pancreas. The only intralobular ducts are long narrow intercalated ducts with a low simple cuboidal epithelium, which open directly into interlobular ducts .

The endocrine pancreas secretes insulin and glucagon directly into the blood stream (capillaries) from irregularly dispersed aggregates of cells forming the pancreatic islets (of Langerhans). The islets are composed of anastomosing cords of cells, numerous capillaries and a fine framework of reticular fibers. They are usually directly surrounded by pancreatic acini, but islets can occur in the interlobular connective tissue. The islets range in size from only a few cells to islets containing thousands of cells. In the latter instance they are large enough to see with the unaided eye. The islets are more numerous in the tail than in any other portion of the pancreas.

== Esophagus ==

=== Slide 131, Middle Esophagus (H&E) ===

== Stomach ==

The gross subdivisions of the stomach are the cardia, the fundus, the corpus (main body) and the pyloric region consisting of a pyloric antrum, a pyloric canal and the pylorus. Only three distinct histological regions are present since the microanatomy of the fundus and corpus is similar. In all regions of the stomach, the surface epithelium consists of tall, columnar mucus-secreting cells. The muscular coat consists of three layers of irregularly arranged smooth muscle.

== Small Intestine ==

The three subdivisions of the small intestine are the duodenum, the jejunum and the ileum. The general microscopic structure is similar in all three parts. In the 21 to 23 feet of small intestine, digestion of food materials continues after leaving the stomach, and its selective absorption occurs.