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Histology Lab-7- Ass. Lec. Wafaa H. M. Alhashimy Dentistry College Second Stage Digestive system : oral cavity , salivary glands ,esophagus and stomach The digestive system is 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 . associated with the digestive tract are the accessory digestive organs : the salivary glands , liver and pancreas . The oral cavity In the oral cavity , food is ingested , masticated (chewed ) and lubricated by saliva for swallowing . because food is physically broken down in the oral cavity , this region is lined by a protective , non keratinized , stratified sequamous epithelium . The lip -The outer region is thin skin a stratified sequamous keratinized epithelium contains hair follicles , sebaceous glands and sweat glands. -The intermediate region (free margin) of the lip coverd the a stratified sequamous non keratinized and the inner are contain skeletal muscle, blood vessls are closed to the lip surface and impart a red color to the lips - Inside region a stratified sequamous non keratinized oral epithelium , beneath the oral epithelium are mucus - secreting labial glands. The tongue Outer layer is the mucosa composet of epithelium and lamina properia (loose C.T.) The epithelium on the ventral surface of the tongue is smooth , the epithelium on the dorsal surface of the tongue is irregular or rough because contain numerous papillae The core of the tongue consists of connective tissue and interlacing bundles of skeletal muscle fibers are random distribution of individual skeletal muscle fibers in the tongue for increased movement during chewing , swallowing and speaking . The posterior one third of the dorsal surface of the tongue is separated from the anterior two thirds by the V-shaped sulcus terminalis. 1 Type of papillae Tongue All papillae on the tongue are coverd by stratified seaquamous epithelium that shows partial or incomplete keratinization . there are four types of papillae are found on the tongue : filiform : most numerous , smollest , elongated conical shape, found in rows parallel to the median sulcus but do not contain taste buds. fungiform : fewer in number than filiform , larger , mushroom shaped and contain a few taste buds on their , most numerous near the tip of the tongue. circumvallate : largest papillae , surrounded by a deep, circular furrow, located along the sulcus terminalis and number from 7-12. Contain Taste buds are located in its lateral surface. Numerous ducts of Serous Ebner's glands drain a watery fluid containing lipases . foliate : poorly developed in humans . Taste buds are pale, barrel-shaped intraepithelial bodies that extend from the basal lamina to the surface.three type of cell found in taste bud including a neuroepithelial cell (taste cell ) , support cells and basal cells (stem cell). The taste buds have a small opening, called the taste pore, receive innervation at their base. The major salivary glands There are three major salivary glands : the parotid (purely serous gland), the submandibular (mixed gland serous & mucous) and the sublingual(mixed gland serous & mucous) . salivary glands are composed of cellular secretory units , tubuloacini and numerous excretory ducts (intercalated Ducts , striated Ducts , Excretory intralobular Ducts , interlobular and interlobar Ducts) . Esophagus The layers of the oesophagus are as follows: mucosa o nonkeratinized stratified squamous epithelium: is rapidly turned over, and serves a protective effect o lamina propria:loose C.T. o muscularis mucosae: smooth muscle . submucosa: Denes irregular C.T., Contains the mucous secreting glands (esophageal glands). 2 muscularis externa (or "muscularis propria"): composition varies in different parts of the esophagus, to correspond with the conscious control over swallowing in the upper portions and the autonomic control in the lower portions: o upper third, or superior part: striated muscle o middle third, smooth muscle and striated muscle o inferior third: predominantly smooth muscles adventitia Gastroesophageal junction The junction between the esophagus and the stomach (the gastroesophageal junction or GE junction) is not actually considered a valve, although it is sometimes called the cardia or cardias. Stomach The three histologic regions of the stomach are the cardia , the fundus and body and the pylorus. the stomach wall are: mucosa The first main layer. This consists of the epithelium and the lamina propria (loose connective tissue), with a thin layer of smooth muscle called the muscularis mucosae separating it from the submucosa . submucosa consists of fibrous connective tissue, The Meissner's plexus is in this layer . the muscularis externa has three layers of smooth muscle instead of two. muscularis externa serosa inner oblique layer: This layer is responsible physically breaks down the food . middle circular layer: the pylorus is surrounded by a thick circular muscular wall ,which controls the movement of chyme into the duodenum. Auerbach's plexus (myenteric plexus) is found between the outer and middle layer. outer longitudinal layer consisting of layers of connective tissue continuous with the peritoneum. 3 Gastric glands Different types of cells are found at gastric glands: Layers of Name gland parietal cells Isthmus Secretion gastric acid and intrinsic factor, Acidophilic Mucous neck mucus gel layer cells fundus chief cells pepsinogen, Basophilic enteroendocrine Defferent hormones to regulate digestive fundus cells system as gastrin, histamine, and somatostatin Rugae is temporary folded of the submucosa of stomach when the stomach is empity formed when contraction of smooth muscle layer . neck Not:serosa covers lower esophagus , stomach ……to colon while adventitia upper part of esophagus and posterior wall of colon. stomach 4