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Download Anatomy and Physiology of the colon, rectum and anus
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Anatomy and Physiology of the main organs of the gastrointestinal tract stomach Functions of the Stomach Storing food Break down of food by releasing enzymes Physical breakdown by muscle contraction Secretes intrinsic factor – for Vit B12 absorption in small intestine Releases food into small intestine Small intestine Functions of Small intestine Major function is – mechanical digestion and absorption What is absorbed? Bile Salts Electrolytes and Vitamins Fats Large Intestine Large Intestine Larger diameter than small intestine Diameter between 2.5 and 7.5 cm 150 cms long Absorbs among other things - water and electrolytes Produces stool fermenting enzymes, vit B + K Converts food waste products into stool Large Intestine 1000-1500mls fluid enters the colon in 24 hours – reduced to 100150mls by absorption Normal transit time from mouth to anus is 32-41 hours ( sweetcorn test) Rectum Rectum Follows curvature of the spine, supported by the pelvic floor muscle. It is able to distend to store faeces The sigmo-rectal junction controls passage of faeces form the sigmoid to rectum Anal sphincter Anal sphincter Held closed by the internal sphincter under involuntary control External sphincter is under voluntary control The is the only part of the bowel we have conscious control over Normal Defaecation When stool is large enough peristalsis moves it into rectum We feel the desire to go – perception of rectal distension Rectum stretches, IAS relaxes, EAS contracts to allow sampling Flatus/stool We adopt sitting position Normal Defaecation Start to push which increases abdominal pressure EAS, IAS and pelvic floor muscle relax to form a funnel Repeated peristalsis moves stool down and out Once finished IAS contracts and the pelvic floor muscle returns to supporting role
