消化-遠程1課件

1、消化系統(tǒng)生理學(xué)概 述消化（digestion）是食物在消化道內(nèi)被分解為小分子物質(zhì)的過程吸收（absorption）消化后的小分子物質(zhì)以及水、無機鹽和維生素，透過消化道粘膜，進入血液和淋巴循環(huán)的過程消化與吸收的基本過程消化道內(nèi)食物的推進與混合消化道的分泌消化道內(nèi)的消化與吸收消化系統(tǒng)的功能運動 分泌 消化 吸收 排泄 消化管的結(jié)構(gòu)消化道平滑肌的電生理特性靜息電位-40-80 mV離子機制Em (selective membrane permeability to K+, Na+, Cl- and Ca2+)Electrogenic Na+-K+ pump慢波 (基本電節(jié)律basic electri

2、cal rhythm)在靜息電位基礎(chǔ)上產(chǎn)生自發(fā)性去極化和復(fù)極化的節(jié)律性電位波動，其頻率較慢 起源于Cajal細胞 interstitial cells of Cajal (ICC) (pacemaker cell)Calcium imaging in ICC-MY from the guinea-pig antrum. A colocalization procedure was used to identify the Rhod-2 signal from ACK2-Alexa 488 labelled ICC-MY. Panel A shows a stack of 30 sequenti

3、al optical sections made in the Z optical axis of the ACK2-Alexa 488 signal and the Rhod-2 signal; panels B and C show each signal independently. Panel D shows the stack after the colocalization algorithm was used on each confocal slice, showing that most ICC-MY were well labelled with Rhod-2. It wa

4、s evident from this experiment that some, but not all, ICC-MY were well-labelled with Rhod-2 (see text for more details). The scale bar in panel D is 40 um and it applies to all imagesIntracellularly recorded electrical activity from a guinea-pig antral ICC-MY identified with ACK2-Alexa 488. Panel A

5、 shows a network of ICC-MY labelled with ACK2-Alexa 488 visualized using fluorescence microscopy, and a single ICC-MY impaled with a LY-filled microelectrode. Panel B shows changes in membrane potential recorded intracellularly from an ICC-MY. One slow wave, marked with the horizontal line in Panel

6、B, is shown in Panel C at an expanded time scale. The scale bar is 15 um.慢波 (基本電節(jié)律basic electrical rhythm)幅度: 1015 mV頻率: 312 cpm離子機制Na+-K+ 泵的自發(fā)性節(jié)律性活動Normal BER frequencies in the gastrointestinal system動作電位時程: 1020 ms離子機制:去極化: Ca2+ influx復(fù)極化: K+ efflux 胃腸的神經(jīng)支配及其作用內(nèi)在神經(jīng)系統(tǒng) (intrinsic)自主神經(jīng)系統(tǒng) (extrinsic)

7、內(nèi)在神經(jīng)系統(tǒng)肌間神經(jīng)叢 Myenteric plexus (Auerbachs plexus)粘膜下神經(jīng)叢 Submucosal plexus (Meissners plexus)內(nèi)在神經(jīng)元分泌的神經(jīng)遞質(zhì)Ach, NE, ATP, serotonin, dopamine, cholecystokinin, substance P, vasoactive intestinal polypeptide, somatostatin, leu-enkephalin, met-enkephalin, bombesin, etc.交感神經(jīng)NEInhibitory (-) 自主神經(jīng)系統(tǒng)副交感神經(jīng)Mainly

8、 AChStimulatory (+)從胃腸道來的傳入性感覺神經(jīng)纖維Sensory fibers with their cell bodies in the ENS terminate in the ENSSensory fibers with their cell bodies in the ENS send axons upward through the ANS to terminate in the prevertebral sympathetic gangliaSensory fibers with their cell bodies in the dorsal root gangl

9、ia or in the cranial nerve ganglia send axons to multiple area of the spinal cord or brain stem胃腸反射三種類型Reflexes that are integrated entirely within the enteric nervous systemReflexes from the gut to the prevertebral sympathetic ganglia and then back to the gastrointestinal tractReflexes from the gut

10、 to the spinal cord or brain stem and then back to the gastrointestinal tract胃腸激素胃腸激素胃腸道內(nèi)分泌細胞合成和釋放的生物活性化學(xué)物質(zhì)作用調(diào)節(jié)消化腺的分泌和消化道的運動 調(diào)節(jié)其他激素釋放 營養(yǎng)作用 胃腸激素四種主要類型胃泌素 Gastrin促胰液素 Secretin膽囊收縮素 Cholecystokinin (CCK)抑胃肽 Gastric inhibitory peptide (GIP) 內(nèi)臟循環(huán)Splanchnic circulationBlood supply to the intestines throug

11、h the mesenteric webMicrovasculature of the intestinal villus胃內(nèi)消化Digestion in the stomach胃液Gastric juice性質(zhì)pH 0.91.51.52.5 L/day主要成分鹽酸 Hydrochloric acid 胃蛋白酶原 Pepsinogen粘液 Mucus內(nèi)因子 Intrinsic factor 鹽酸Hydrochloric acid 由胃底腺中的壁細胞（parietal cell）分泌分泌量Basal: 05 mmol/hMaximal: 2025 mmol/h分泌機制主動轉(zhuǎn)運Active tra

12、nsportHuge H+ gradient (3 million)鹽酸的作用殺滅隨食物進入胃內(nèi)的細菌激活胃蛋白酶原，提供必要的酸性環(huán)境 引起促胰液素的釋放 有利于鐵和鈣在小腸內(nèi)吸收 胃蛋白酶原 PepsinogenMW: 42,500由胃底腺的主細胞（chief cell）分泌在鹽酸作用下，或在酸性條件下，通過自身催化轉(zhuǎn)變?yōu)橛谢钚缘奈傅鞍酌?（pepsin）Active pepsin (MW: 35,000)作用ProteinsProteosesPeptonesPolypeptidesPepsin粘液 Mucus由表面上皮細胞、胃底腺的頸粘液細胞、賁門腺和幽門腺共同分泌 作用潤滑減少粗糙食物

13、對胃粘膜的機械性損傷 Mucus-HCO3- barrier內(nèi)因子 Intrinsic factor分子量約6萬的糖蛋白 由壁細胞分泌促進維生素B12的吸收 其他酶的分泌Gastric lipaseGastric amylaseGelatinase胃液分泌的調(diào)節(jié)引起胃液分泌的因素乙酰膽堿Acetylcholine (+ all secretory cells)胃泌素Gastrin (+ parietal cells)組胺Histamine (+ parietal cells)胃液分泌的調(diào)節(jié)神經(jīng)調(diào)節(jié)Nervous regulation短反射途徑Short reflex pathways Shor

14、t excitatory reflexes: mediated by cholinergic neurons in the plexusesShort inhibitory reflexes: mediated by non-adrenergic non-cholinergic (NANC) neurons胃液分泌的調(diào)節(jié)神經(jīng)調(diào)節(jié)長自主神經(jīng)途徑Long autonomic pathwaysLong excitatory reflexes: parasympatheticLong inhibitory pathways: sympathetic胃液分泌的調(diào)節(jié)激素調(diào)節(jié)ExcitatoryAChHis

15、tamineGastrinInhibitorySomatostatin Secretin5-hydroxytryptamine (5-HT) Prostaglandin消化期的胃液分泌 頭期Cephalic phase胃期Gastric phase腸期Intestinal phase胃液分泌的抑制 鹽酸 脂肪 高張溶液 胃的運動Motor function of the stomachProximal stomachcardiafundus corpus (body)Distal stomachantrum pylorus pyloric sphincter 胃運動的主要形式容受性舒張 Rec

16、eptive relaxation當(dāng)咀嚼和吞咽時，食物對咽、食管等處感受器的刺激可引起胃頭區(qū)肌肉的舒張Storage function (1.01.5 L)Vago-vagal reflex蠕動 Peristalsis BER in the stomach Contractions in the empty stomachMigrating Motor Complex (MMC)Periodic waves of contraction, which move along the gastrointestinal tract from stomach to colon Purpose of this activity: to sweep debris out of the digestive tract during the interdigestive periodMMCs can lead to hunger contractions, which are associated with discomfort, referred to as hunger pains胃的排空Emptying of the stomach胃內(nèi)食糜由胃排入十二指腸的過程稱為胃排空（gastric emptying） Emptying rateFluid viscousSmall part