Zahraa Ahmed Buthaina Al-Ezzi Digestive System Zahraa Ahmed Buthaina Al-Ezzi

The digestive system The digestive system is a long hollow tube or tract that starts at the oral cavity and terminates at the anus. The system consists of the oral cavity, esophagus, stomach, small intestine, large intestine, rectum, and anal canal. The oral cavity consists of the mouth and its structures, which include the tongue, teeth and major and minor salivary glands, and tonsils.

The Lips The oral cavity is formed, by (the lips and cheeks.) The lips are lined by a very thin skin covered by a stratified squamous keratinized epithelium. Blood vessels are close to the lip surface, imparting a red color to the lips. The outer surface of the lip contains hair follicles, sebaceous glands, and sweat glands. The lips also contain skeletal muscle called orbicularis oris M the outer lining changes to a thicker, stratified squamous non keratinized oral epithelium. Beneath the oral epithelium are found mucus-secreting labial glands.

The lip structure: 1- The external surface 2- The internal surface 3- the vermilion margin (red margin)

The external surface of the lip: is covered with thin skin formed of epidermis and dermis with the associated hair follicles, sebaceous glands and sweat glands. underbeneath the skin, bundles of circular skeletal muscle of the orbicularis oris M. The internal surface of The lip: Lines by mucous membrane which is formed of: stratified squamous non-keratinized epithelium (thicker than that of epidermis of the external surface) lamina propria : formed  C.T. contain; Blood vessels, lymphatic Vessels , nerves and group of labial minor salivary glands (mucous acini)

The Vermilion (red) margin of the lip: is continuous with the thin skin of the ext. surface of the lip covered by modified skin characterized by : transparent epithelium; formed of stratified squamous non-keratinized epithelium without hair follicles, sebaceous glands or sweat glands. deeply and vascular dermal papillae (giving the red color of the lip margin), highly supplied with nerves.

The Tongue The tongue is a muscular organ located in the oral cavity. The core of the tongue consists of connective tissue and interlacing bundles of skeletal muscle fibers. The distribution and random orientation of individual skeletal muscle fibers in the tongue allows for increased movement during chewing, swallowing, and speaking.

Papillae The epithelium on the dorsal surface of the tongue is irregular or rough owing to numerous elevations or projections called papillae. All papillae on the tongue are covered by stratified squamous epithelium that shows partial or incomplete keratinization. In contrast, the epithelium on the ventral surface of the tongue is smooth. There are four types of papillae on the tongue: filiform, fungiform, circumvallate, and foliate.

3.Circumvallate papillae 4. Foliate Papillae Filiform Fungiform . 3.Circumvallate papillae 4. Foliate Papillae

FIGURE 16. 5 ▲ Lingual papillae. a FIGURE 16.5 ▲ Lingual papillae. a. Structurally, the fi liform papillae are posteriorly bent conical projections of the epithelium. These papillae do not possess taste buds and are composed of stratifi ed squamous keratinized epithelium. 45. b. Fungiform papillae are slightly rounded, elevated structures situated among the fi liform papillae. A highly vascularized connective tissue core forms the center of the fungiform papilla and projects into the base of the surface epithelium. Because of the deep penetration of connective tissue into the epithelium (arrows), combined with a very thin keratinized surface, the fungiform papillae appear as small red dots when the dorsal surface of the tongue is examined by gross inspection. 45. c. In a section, foliate papillae can be distinguished from fungiform papillae because they appear in rows separated by deep clefts (arrows). The foliate papillae are covered by stratifi ed squamous nonkeratinized epithelium containing numerous taste buds on their lateral surfaces. The free surface epithelium of each papilla is thick and has a number of secondary connective tissue papillae projecting into its undersurface. The connective tissue within and under the foliate papillae contains serous glands (von Ebner’s glands) that open via ducts into the cleft between neighboring papillae. 45. d. Circumvallate papillae are covered by stratifi ed squamous epithelium that may be slightly keratinized. Each circumvallate papilla is surrounded by a trench or cleft. Numerous taste buds are on the lateral walls of the papillae. The dorsal surface of the papilla is smooth. The deep trench surrounding the circumvallate papillae and the presence of taste buds on the sides rather than on the free surface are features that distinguish circumvallate from fungiform papillae. The connective tissue near the circumvallate papillae also contains many serous-type glands that open via ducts into the bottom of the trench. 25

Teeth are a major component of the oral cavity and are essential for the beginning of the digestive process. Teeth are embedded in and attached to the alveolar processes of the maxilla and mandible. Teeth are made up of three specialized tissues: • Enamel that covers the crown of the tooth. Dentin, it lies deep to the enamel in the crown and cementum in the root. .

• Cementum, covering the dentin of the root of the teeth • Cementum, covering the dentin of the root of the teeth. Dental pulp The dental pulp (also called "the nerve" of the tooth) is the central part of the tooth and is filled with soft connective tissue that contains blood vessels and nerves.

The Tongue Circumvallate papillae/ blue pointer refer to taste buds The Tongue Circumvallate papillae/ blue pointer refer to taste buds.//red pointer refer to Von Ebner's gland (serous gland)

tooth