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Ebook Difiore’s atlas of histology with functional correlations (7/E): Part 2

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Part 2 book “Difiore’s atlas of histology with functional correlations” has contents: Digestive system - oral cavity and salivary glands, digestive system - esophagus and stomach, respiratory system, urinary system, endocrine system, male reproductive system, female reproductive system, organs of special senses, and other contents. | GRBQ349-3528G-C11[234-261].qxd 10/19/2007 06:31 PM Page 235 Aptara(PPG Quark) CHAPTER 11 Digestive System: Oral Cavity and Salivary Glands 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. Associated with the digestive tract are the accessory digestive organs, the salivary glands, liver, and pancreas. The accessory organs are located outside of digestive tract. Their secretory products are delivered to the digestive tract through excretory ducts that penetrate the digestive tract wall (Overview Figure 11.1: Oral Cavity). 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, nonkeratinized, stratified squamous epithelium, which also lines the inner or labial surface of the lips. The Lips The oral cavity is formed, in part, 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. Inside the free margin of the lip, the outer lining changes to a thicker, stratified squamous nonkeratinized oral epithelium. Beneath the oral epithelium are found mucus-secreting labial glands. 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 .