✓Water and electrolytes absorbed throughout the intestine by paracellular route passively and by transcellular route actively
✓ 100ml of water by faces passes by stool whear as total fluid enters into the GIT is 8 litre
✓Small intestine give protection by physical and immunological mechanism
✓ Physical defense mechanism exeryd by host bacteria,mucins and secreted antibacterial products including defendins and immunoglobulins.Also impermeable epithelial brush border,pattern recognition receptor on cell surface or intracellularly.
✓ Immunological defense mechanism:
∆MALT constitute 25% of total lymphatics which is the heart of adaptive immunity
∆ In the Peter's patches B lymphocytes differentiate into plasma cell following exposure to any Antigen and enters into the blood stream through mesenteric lymph node and then thoarcic duct.
∆ Plasma cell come back to lamina propria producing IgA which secreted in the limem
∆ T cell localise site of Antigen and macrophages phagocytose foreign materials and also sectte cytokines mediating inflammation
∆ Activation of mast cell causes release of IgE.
✓ Exocrine function of pancreas is crucial for digestion of carbohydrates,fat and protein.
✓Proenzymes secreted by from the acinar cell by stimulation of CCK,Secrtin,VIP, Ach,Bombesin, Substance P.
✓ Bicarbonate rich fluid secrted from ductilar cell by stimulation of Secrtin which maintains optimum pH for enzyme action.
✓ Colon act as storage organ also absorbs electrolytes and water having 2 movement Segmentation (mixing,ring contraction) and propulsive (peristaltic)
✓Propulsive movement occurs several times a day causing passage of faeces to rectum.
✓All activities of colon stimulated after meals due to release of hormone such as 5-HT,Serotonin,motilin,CCK(Gastrocolic reflex)
✓During defecation there is contraction of abdominal muscles,increased intrabdominal pressure(Due to Valsalva monoevre) and relaxation of anorectal muscle occur.
✓Human body contains 10^14 microbiota outnumbering the host cells
✓Genom of the microbiota 100 fold or more than host
✓Microbiotoa means the microorganism resides in particular area and microbiome means their genome
✓Metabolic capacity of microbiota is equivalent to liver
✓Example of microbiota phylum in different parts of the body include Firmicutes,Bacteroids,Proteobacteria and Actinobacteria
✓There is degree of heredity but diet,drugs,physical activity,smoking,stress,natural aging has impact on microbiota
✓Intestinal microbiota acquired by the age of 2 years.
✓Dysbiosis between different components of microbiota asscoited with disease such as IBD, Colorectal cancer,liver disease including HCC,and also pathology outside GIT such as diabetes,asthma,obesity,CVS disease,psychiatric disorders such as depression.
✓Control of GOT function modulated by hormonal and neuronal factors
✓Centarl nervous system(CNS), Autonomic nervous system(ANS),Enteric nervous system(ENS) interact to regulate gut function.
✓ANS has parasympathetic pathway from vagal and sacral efferent causing increased smooth muscle tone,promoting sphicter relaxation(Cholinergic activity).And Sympathetic pathway releasing noradrenaline reduces smooth muscle tone and stimulate sphicter contraction.
✓ ENS senses contents and condtions in conjunction to ANS and regulates motility,fluid exchange,secrtion,blood flow etc.
✓ENS makes two layers of neuronal networks along the length of gut intrinsic the gut wall called Menteric(Auerbach's) plexus having motor control in smooth muscle layer and Meissner's plexus in the submucosal layer having secrtory control on epithelium, enteroendocrine cells and blood vessels.
✓ENS can act autonomously by variety of transmitter such as Ach, noradrenaline,5-HT,nitric oxide, Substance P,calcitonin related peptide
✓Peristaltic movement of the gut triggered by wall distension can be influenced by innervation innervation but independently can occur.Basically electrical rytm originating from interstitial cells of Cajal in circular layer of smooth muscle which are stellate cells of mesenchymal origin calling 'pacemaker" of gut.
✓Migarating motor complexes are waves of contraction speeding from stomach to ileum occuring about 5 per minute every 90 minute or so between meals and fasting and inhibited by eating.
✓Gut hormone includes Gastrin,Somatostatin,CCK,Secrtin,Motilin,GIP,VIP,GLP-1,Ghrelin,Peptide YY.
✓Peptide YY secrted from ileum and colon,stimulated by feeding and Modulates satiety.
✓Ghrelin secrted from stomach(oxyntic cell),stimulated by fasting inhibited by eating,stmulates appetite,acid secretion and gastric emtying.
✓Vasoactive intestinal peptide or VIP released from nerve fibres throughout the GIT stimulation unknown has causes vasodilation,relaxes smooth muscle,stimulyaes water and electrolytes secretion.
✓Glucagon like Peptide or GLP-1 secrted from L cells of Ileum and colon, stimulated by carbohydrates, protein,fats.It causes stimulation of insulin release,inhibit acid secretion and gastric emtying.
✓Gastric inhibitory peptide or GIP comes from K cells of Duodenum and from Jejunum, stimulated by glucose and fat.It stimulated insulin release,inhibits gastric secretion but enhances satiety.
✓Motilin released from Duodenum,Jejunum & Colon(Mo cells) stimulated by fasting and dietary fat.It regulates Peristaltic activity including migrating motor complexes.
✓Secretin comes from duodenum and Jejunum (S cells) stimulated by Dudenal acids and fatty acids .It stimulates pancreatic fluid and bicarbonate secretion, Decreases acid secrtion,Reduces gastric emtying.
✓Cholecystokinin(CCK) secrted from Duodenum Ang Jejunum (I cells) also from ileal and colonic nerve ending stimulated by products of protein digestion,fat and fatty acids,Suppressed by trypsin.It stimulates pancreatic enzyme secrtion,stimulates gallbladder contraction,Relaxes sphicter of Oddi,Modulates satiety,Decrease gastric acid secrtion,Reduces gastric emptying,Regulates pancreating growth.
✓Somatostatin released from D cell throughout the gut stimulated by fat ingestion which inhibits Gastrin and insulin secretion, Decreases acid secretion, Decreases absorption,Inhibit pancreatic secretion.
✓Gastrin secreted from G cells of stomach stimulated by protein ingestion, suppressed by acid and Somatostatin.It stimulates gastric acid secrtion,stimulates growth of gastrointestinal mucosa.
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