پاورپوینت پاتوفیزیولوژی مری (pptx) 118 اسلاید

دسته بندی : پاورپوینت

نوع فایل : PowerPoint (.pptx) ( قابل ویرایش و آماده پرینت )

تعداد اسلاید: 118 اسلاید

قسمتی از متن PowerPoint (.pptx) :

Esophageal pathophysiology The esophagus is approximately 25 cm in length measured from its origin in the neck just below the cricopharyngeus muscle (C6 level) to its termination in the abdomen at the gastric cardia (T11 level). The lumen of the esophagus is collapsed at rest, but can distend to a diameter of approximately 40 mm to accommodate a swallowed bolus. The esophagus veers slightly to the left of the midline behind the heart, and passes into the abdomen through the diaphragmatic hiatus. At the T4 level in the thorax, the esophagus is indented on its left side by the aortic arch. This pulsating indentation can be noted during endoscopic examination at a distance of approximately 23 cm from the incisor teeth. Just distal to the aortic arch, the left main bronchus causes another indentation on the left anterior aspect of the esophagus. Normally, approximately 2 cm of the distal esophagus are located within the abdomen. On endoscopic examination, the esophago-gastric junction ordinarily is encountered approximately 40 cm from the incisor teeth. Histology - Stratified Squamous Epithelium This slide shows the non-keratinizing, stratified squamous epithelium that lines most of the normal esophagus. The squamous cells (S) contain glycogen. Neutrophils and eosinophils are not found normally in the epithelial layer. Note that the normal basal zone (B) comprises less than 15% of the total thickness of the squamous epithelium. The lamina propria protrudes into the epithelial layer in the form of papillae (P). Normally, the papillae do not extend more than 50% of the distance to the epithelial surface. The muscularis of the esophagus is comprised of an outer layer of longitudinal muscle and an inner layer of circular muscle. Contraction of the longitudinal layer causes the esophagus to shorten, whereas contraction of the circular muscle causes the squeezing motion necessary for peristalsis and for closure of the esophageal sphincters. In general, the proximal one-third of the esophagus is lined by striated muscle, whereas smooth muscle lines the distal two-thirds. the proximal esophagus is subject to diseases that affect striated muscle and its central nervous system innervation (e.g. polymyositis, myasthenia gravis), whereas the distal esophagus is susceptible to diseases of smooth muscle and the intramural neurons that supply the smooth muscle fibers (e.g. scleroderma, achalasia). The striated muscle of the proximal esophagus is supplied by somatic efferent fibers carried in the vagus nerve. The cell bodies of these somatic efferent fibers are located in the nucleus ambiguus, and the fibers terminate in motor end plates on the striated muscle. The innervation of the smooth muscle in the distal esophagus is more complex. To the distal esophagus, the vagus nerve carries preganglionic fibers whose cell bodies lie in the dorsal motor nucleus. The preganglionic fibers release acetylcholine, and supply at least two important types of postganglionic effector neurons located within the wall of the esophagus. One type of effector neuron excites the smooth muscle by releasing acetylcholine. The other type of postganglionic effector neuron inhibits the smooth muscle, Nitric oxide (NO) and, perhaps, VIP function as inhibitory neurotransmitters. The upper esophageal sphincter (UES) separates the pharynx from the esophagus. By remaining closed in its basal state, the UES prevents air from entering the gastrointestinal tract during inspiration, and protects the airway by preventing the reflux of material from the esophagus into the pharynx. The UES normally relaxes with swallowing to allow ingested material to enter the esophagus. The UES also relaxes during belching and vomiting to permit the egress of air and other material from the esophagus into the mouth. Manometrically, the UES extends 3 to 4 cm in length. It appears that the UES is comprised of at least three groups of striated muscles: 1-distal portion of the inferior pharyngeal constrictor muscle, 2-the cricopharyngeus muscle, 3- muscle of the proximal esophagus.