physiology-15.消化与吸收1.pptVIP

第六章 消化和吸收 Digestive organs include oral cavity, pharynx, esophagus, stomach, small large intestine separated by sphincters Accessory organs include teeth, tongue, salivary glands, liver, gallbladder, pancreas Mucosa Is the absorptive secretory layer lining lumen of GI tract In places is highly folded with villi to increase absorptive area Contains lymph nodules, mucus-secreting goblet cells, thin layer of muscle Submucosa Is a thick, highly vascular layer of connective tissue where absorbed molecules enter blood lymphatic vessels Contains glands nerve plexuses (submucosal plexus) that carry ANS activity to muscularis mucosae Muscularis Is responsible for segmental contractions peristaltic movement through GI tract Has an inner circular outer longitudinal layer of smooth muscle Activity of these layers moves food through tract while pulverizing mixing it Myenteric plexus between these layers is major nerve supply to GI tract Includes fibers ganglia from both Symp Parasymp systems Serosa Is outermost layer; serves to bind protect Consists of areolar connective tissue covered with layer of simple squamous epithelium 一、消化道平滑肌的生理特性 Movement of food thru GI tract by means of: Ingestion（进食）--taking food into mouth Mastication（咀嚼）--chewing food mixing it with saliva Deglutition（吞咽）--swallowing food Segmentation(分节运动）--mixing or churning food Peristalsis（蠕动）--rhythmic wave-like contractions that move food thru GI tract Slow waves are produced by non-neuronal interstitial cells of Cajal (ICC) Conducted to smooth muscle via gap junctions Slow waves spread from 1 smooth muscle cell to another thru gap junctions When slow waves exceed threshold, they trigger APs in smooth muscle by opening V-gated Ca2+ channels Influx of Ca2+ produces depolarization phase of AP stimulates contraction Repolarization via K+ efflux Electrical and Contractile activity are modified by ANS(extrinsic and intrinsic) activity ACh from Parasymp increases amplitude duration of slow waves