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Gastrointestinal GUCASGI tract between: - Mouth - Anal canal2 Main functions • Digestion – to process and breakdown food • Absorption- transfer nutrients to circulation2 Groups of organs • Digestive tract • Accessory organs (salivary glands, gallbladder, liver, pancreas,) Salivary glands –seromucous solution, helps buffer the mouth pH, protects the surface of mouth and gut, antimicrobial action, maintains tooth structure , aids in The taste, aids to some extent with digestion (lingual lipase accessory Gall bladder – the gall bladder stores and concentrates bile, produced by liver, helps organs with fat digestionTHE GI TRACT • Oral cavity • Pharynx • Oesophagus • Stomach • Small intestine • Large intestinePharynx • 10-15cm • Air and food • 3 parts – Nasopharynx, Oropharynx, LaryngopharynxOesophagus • 20-25 cm • food to the stomach • Peristaltic movements • 3 muscle types: upper skeletal, middle mixed, lower smoothThe stomach • been eaten to form chymehat's • Located in upper third of stomach (Left hypochondrium) • Chyme moves through pyloric sphincter to enter the duodenum • Rugae: folds to increase surface area • Simple columnar epithelium (throughout GI tract)Three muscle layers of the stomach - Digestion/absorption The small intestine - Three parts DUODENUM -Secretions from the pancreas and bile, digestions of fats protiens and carbohydrates, bicarbonate secretions(alkaline) -Secretions enter from the major duodenal papilla JEJENUM ILEUMLayers of the duodenumLarge intestine • 150 cm long • 4 parts: colon, descending colon,rse sigmoid colon • Two flexures: Hepatic flexure, splenic flexureThe caecum • Most proximal part of large intestine • Found in the right iliac fossa • Can be palpated if inflammation or enlargement • Between the ilium caecum is the ileocecal valve prevents bowel refluxAscending colon The colon begins as the ascending colon, a retroperitoneal structure which ascends superiorly from the caecum. Transverse colon The transverse colonextends from the right colic flexure to thepleen. The transverse colon is the least fixed part of the colon, and is variable in position (it can dip into the pelvis in tall, thin individuals). Unlike the ascending and descending colon, the transverse colon is intraperitoneal Descending colon The colon then moves inferiorly towards the pelvis– and is called the descending colon. It is retroperitoneal in the majority of individuals, but is located anteriorly to the left kidney When the colon begins to turn medially, it becomes the sigmoid colon. Sigmoid colon The 40cm long sigmoid colon is located in the left lower quadrant of the abdomen, extending from the left iliac fossa to the level of the S3 vertebra. This journey gives the sigmoid colon its characteristic “S” shape.Right hepatic flexure Left splenic flexure SPECIALISED STRUCTURES - Taenia Co -li longitudinal bands of smooth muscle outside the ascending, transverse and descending colon, isn’t continuous - Haustra/ haustrations- circumferential contraction of the inner muscle layer of the colon - Appendice epiloicae- Pouches of peritoneum filled with fat mainly on the transverse and sigmoid colonHistology - Simple columnar - Goblet cells – produce mucous to protect intestinal lininngTHE GUT Coeliac trunk – foregut , oesophagus till ½ duodenum Superior mesenteric artery- midgut, last half of duodenum till first 2/3 of transverse colon Inferior mesenteric artery- hind gut, last 1/3 of transverse colon till rectum VENOUS DRAINAGEQuestions ?