Part I

• The Digestive Tract is a long tube extending from the mouth to the anus.
• Each part of the Digestive Tube has a similar structure.
• The Digestive Tract is associated with glands which are situated outside the tube but delivering their secretions into it.
• Digestion is a process whereby the food material is converted into substances that can be absorbed into the circulation.
• The process of digestion involves different steps: Breaking down of food material to small pieces, absorption of the food material into the circulation, and elimination of useless or toxic materials by fecal excretion.
• The Digestive Tract has three major parts: The Oral Cavity, The Tubular Digestive Tract, and The Major Digestive Glands.
• The Oral Cavity is the entrance to the Digestive Tract and its main functions are the breaking down of the food material and the hydrolyzation of the carbohydrates.
• The Oral Cavity has two parts: Vestibulum oris, which is closed by tooth and upper and lower lips, and Cavum oris proprium, which is closed by tooth, cheeks and palate.
• The Lips are macroscopic characteristics of the Oral Cavity and their microscopic structure is composed by striated muscle.
• Striated ducts are tall, columnar in shape with basal striation (basal invaginations of the plasma membrane with mitochondria).
• Pure serous acini are rare in the major salivary glands.
• Intercalated ducts commence from the lumen of the acini and are covered with small, flattened epithelial cells; myoepithelial cells may be present between the duct cells and basal lamina.
• Intralobular ducts are located inside in the lobules; they tend to be greater in diameter and longer than the striated ducts with simple columnar epithelium.
• Saliva (1,5 - 2l/24h) is a liquid containing water, salts, mucin and enzymes (ptyalin and maltase that split the carbohydrates).
• The epithelial cells of the striated ducts are associated with fluid absorption from the lumen to the blood vessels.
• The major salivary glands have very similar duct systems.
• The main excretory ducts open in the oral cavity; with pseudostratified and finally multistratified squamous epithelium; deliver saliva.
• Interlobular ducts are located in the septae; with columnar to pseudostratified epithelium.
• The papillae circumvallatae are the biggest taste buds, located along the V-shaped sulcus (sulcus terminalis), surrounded by a circular furrow, and have numerous taste buds located on the lateral walls.
• The muscles of the tongue are striated, intrinsic (confined to the tongue) and extrinsic (originate outside), including the muscles genioglossus, styloglossus, and hyoglossus.
• The papillae foliatae are taste buds located on the lateral walls of the tongue, specifically for children.
• The intrinsic muscle of the tongue, the longitudinalis inferior, is located between the genioglossus and hyoglossus.
• The taste buds are responsible for the sense of taste, are located in the epithelium of the papillae vallatae and fungiformes, are pale, barrel-shaped bodies with a laminated appearance, have an external opening (outer taste pore) and a small pit in the base (inner taste pore), and have three types of cells: neuroepithelial cells, supporting cells, and basal cells.
• The transversus and verticalis muscles are part of the intrinsic muscle of the tongue.
• The ducts of serous glands (Ebner’s) open in the furrow of the papillae circumvallatae.
• The core of the tongue consists of striated muscle fibers and glands (glandulae linguales) between them.
• The glands of the tongue are mixed acini near the tip, serous acini, and mucous acini in the base of the tongue.
• The filiform papillae are taste buds located on the lateral walls of the tongue.
• The intrinsic muscle of the tongue, the longitudinalis superior, is located under the mucous membrane.
• On the upper surface of the tongue, the mucosa shows numerous protuberances, papillae, which are located in rows parallel to the V-shaped groove and show signs of cornification.
• Papillae fungiformes are located near the tip of the tongue and are disposed between the folds of the mucous membrane.
• The tongue is covered by a mucous membrane, tunica mucosa, which includes lamina epithelialis, a multistratified squamous epithelium, and lamina propria, a loose connective tissue that shows secondary papillae with a rich vascular plexus.
• The tongue is located in the oral cavity and has two main parts: the root (base) which is the posterior third, and the body which is the anterior two-thirds.
• Between lamina propria and the muscle core of the tongue is a layer of elastic and collagen fibers, aponeurosis linguae (stratum reticulare).
• The mucous membrane of the tongue forms folds, including Plica e fimbriata e, Frenulum linguae, Caruncula e sublingual e s, and Plica e sublingual e s.
• The mucous membrane on the root of the tongue passes to the epiglottis and forms three folds: Plica glossoepiglottica mediana, Plicae glossoepiglotticae laterales, and Valleculae epiglotticae.
• The under-surface of the tongue is smooth, freely movable and underlain by a tela submucosa.
• The surface epithelium of the root of the tongue forms many depressions, termed cryptae.
• Papillae filiformes are very similar to papillae, but are bigger.
• The root of the tongue has a nodular, irregular surface due to the presence of lymphatic nodules (tonsilla lingualis).