Lower GI Anatomy - Lecture Slides.pptx

Lower Gastrointestinal tract Gross and Microanatomy Where opportunity creates success Dr Anthony Adefolaju...

Lower Gastrointestinal tract Gross and Microanatomy Where opportunity creates success Dr Anthony Adefolaju Lecturer in Medical Sciences (Anatomy) [email protected] UM1010 - GI Block Macro Learning Outcomes Describe the functional anatomy of the digestive tract (oral M1.I.GAS.AN cavity, oesophagus, stomach, duodenum, jejunum, ileum, A1 caecum and colon), accessory digestive organs (salivary glands, liver, gallbladder, pancreas) and the spleen. M1.I.GAS.AN Outline the major structures of the neurovascular supply to A2 the gastrointestinal system. Describe the organisation and clinical significance of the M1.I.GAS.AN parietal and visceral peritoneum, the greater and lesser sacs, A3 mesenteries and peritoneal ‘ligaments’. M1.I.GAS.AN Understand specific common clinical examples associated A4 with the gastrointestinal system. 1. Functional anatomy of the small intestine (duodenum, jejunum, ileum) 2. Functional anatomy of the large intestine (cecum, appendix, colon, What we will rectum, and anal canal) cover in this session 3. Their neurovascular supply 4. Lower GI histology. Introduct ion The digestive tract and associated organs.  Derivatives of the gut Regions of the GI tract derived from the primitive fore, mid, hindgut. Small intestine - Duodenum Location Shape Parts Relations The derivatives of the primitive midgut …… begins from distal half of the 2nd part of the duodenum. The 4th part leads to the jejunum at the duodenojejunal flexure Small intestine – Jejunum and Ileum Length - 2.5m Location Width - 2- 4cm Length Parts Relations Internal features Length - 3m Width - 2- 3 cm Small intestine – Jejunum and Ileum Location Most of the Length jejunum lies in the Parts left upper Relations quadrant whereas Internal features most of the ileum lies in the right lower quadrant  Small intestine – Jejunum and Ileum Histolo gy  Plicae circulares  Simple columnar epith.  Villi  Microvilli  Goblet cells  Enterocyte (absorbs nutrients)  Paneth cells (innate immunity)  Duodenal (Brunner) glands Duodenal glands Histolo (DG) are concentrated in gy the upper  Plicae circulares duodenum. They  Simple columnar epith. are large masses  Villi  Microvilli of compound  Goblet cells tubular mucous  Enterocyte glands, (absorbs nutrients)  Paneth cells (innate immunity) Alkaline mucus  Duodenal from duodenal glands neutralizes (Brunner) the pH of gastric glands chyme and  Compound supplements the tubular mucus from goblet Large intestine Location Length Parts Relations Caecum Internal features Vermiform appendix Ascending colon Transverse colon Descending colon Sigmoid colon Rectum and Large intestine Some unique features. 1. Haustra: These are small pouches. The sacs are formed by the inner circular muscle layer and give the colon its segmented appearance. 2. Omental appendices: These are small, fatty tags or omentum-like projections. 3. Taeniae coli. These Caecum Location Length Parts Relations Internal features Caecum The caecum is the first part of the large intestine inferior to the ileocecal opening. It is located in the right iliac fossa.  Appendix Location Length Parts Relations Internal features Vermiform appendix L. vermis, wormlike 6–10 cm long The appendix is a significant part of the MALT (mucosa-associated lymphoid tissue) with its lamina propria and submucosa filled with lymphocytes and lymphoid follicles (L).  Appendix Variation s in position of the appendix Retrocaecal appendix occurs in 64% of 10,000. Pelvic appendix - 32% Sub-caecal appendix 2% Others share 2% Colon Location Length Parts Relations Internal features Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Location Length Parts Relations Internal features The rectum is the Flexures: terminal part of the The sacral flexure of the rectu large intestine. Upper right flexure Retroperitoneal and Middle left flexure Lower right flexure Subperitoneal) the perineal flexure 12 -15 cm Large intestine Histolo gy Epithelium Goblet cells Simple columnar epithelium Intestinal glands Lymphatic nodules Muscle Circular layer Longitudinal layer (taenia coli) Rectum & Anal canal Location Parts Relations Internal features The anal canal is the terminal part of the entire digestive tract. About 3.5 cm Anal columns (clinical significance) ATZ – Transitional zone - simple columnar and Anal canal Transitions occurring at the pectinate line. superior to the pectinate line - vessels and nerves are visceral inferior to the pectinate line - vessels and nerves are parietal or Anal canal – Clinical significance Haemorrhoids Predisposing factors? Faecal incontinence the inability to control bowel movements, causing stool (faeces) to leak Rectum & reflections of the peritoneum recto-uterine pouch. rectovesical pouch. pararectal fossae Blood Supply - Abdominal viscera  Abdominal aorta  Coeliac trunk  Renal artery  Common iliac artery  Internal iliac artery  Superior mesenteric artery  Inferior mesenteric artery Blood Supply - Abdominal viscera Why are they called mesenteric arteries? Superior Mesenteric Artery Branch es Jejunal and ileal arteries Ileocolic artery Right colic artery Middle colic artery Superior Mesenteric Artery Branch es Jejunal and ileal branches Ileocolic Right colic Middle colic The jejunum (A) has longer vasa recta (straight arteries) while the ileum (B) has more prominent arterial arcades compared to Inferior mesenteric artery Branch es Left colic Sigmoid arteries (2 – 4) Superior rectal Marginal artery Anastomotic connections between the Sup and Inf mesenteric arteries form the marginal artery. Porto-Caval anastomosis Tributaries of hepatic portal vein and portal– systemic anastomose s. Anastomoses provide a collateral circulation in cases of obstruction in the liver or portal vein. Nerve supply Innervat ion The gut receives innervation from the autonomic nervous system: Innervation Actual location of the plexuses in relation other structures Effects of ANS in the gut In general, sympathetic stimulation causes inhibition of gastrointestinal secretion and motor activity, and contraction of gastrointestinal sphincters and blood vessels. Conversely, parasympathetic stimuli typically Abdominal imaging 1. Functional anatomy of the small intestine (duodenum, jejunum, ileum) 2. Functional anatomy of the large What we intestine (cecum, appendix, colon, covered in rectum, and anal canal) this session 3. Their neurovascular supply 4. Lower GI histology. Additional resources Gray's anatomy for students https://uclan.alma.exlibrisgroup.com/leganto/public/44UOCL_INST/citation/55864838200 03821?auth=SAML Abrahams' and McMinn's clinical atlas of human anatomy https://uclan.alma.exlibrisgroup.com/leganto/public/44UOCL_INST/citation/55865199800 03821?auth=SAML Complete Anatomy https://uclan.alma.exlibrisgroup.com/leganto/public/44UOCL_INST/citation/55865371200 03821?auth=SAML Wheater's functional histology : a text and colour atlas https://uclan.alma.exlibrisgroup.com/leganto/public/44UOCL_INST/citation/55866190800 Macro Learning Outcomes Describe the functional anatomy of the digestive tract (oral M1.I.GAS.AN cavity, oesophagus, stomach, duodenum, jejunum, ileum, A1 caecum and colon), accessory digestive organs (salivary glands, liver, gallbladder, pancreas) and the spleen. M1.I.GAS.AN Outline the major structures of the neurovascular supply to A2 the gastrointestinal system. Describe the organisation and clinical significance of the M1.I.GAS.AN parietal and visceral peritoneum, the greater and lesser sacs, A3 mesenteries and peritoneal ‘ligaments’. M1.I.GAS.AN Understand specific common clinical examples associated A4 with the gastrointestinal system.