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Anatomy: GI & Abdomen – Pt. 1 Stomach, SI, Peritoneum, Liver & Colon Dr. Steven Gopaul Fthndation Year 1 Doctor, EOE 26March 2022 @BRITISHINDIANMEDIC@BIMAIAT@BINDIANMEDICS BIMA Anatomy Series Dr Steven Gopaul is an FY1 Foundation Doctor with a keen interest in General Surgery and Urology. Steven has a strong interest in medical education and has delivered over 10 lectures to medical students. In his free time, he likes to watch/play any type of sport and stock investing. Dr Steven Gopaul FY1 , EOE Deanery BIMA Anatomy Series Outline 1. Introduction 2. Stomach 3. Small intestines 4. Liver 5. Peritoneum 6. Colon 7. Final thoughts BIMA Anatomy Series Learning objectives 1. Leave with appropriate knowledge 2. Understand the relevance of the anatomy 3. Be able to confidently identify landmarks in spotters 4. Consolidation tips for dissection and final exams BIMA Anatomy Series Introduction • Mouth to anus. • functions are: ingestion (mouth), secretion (stomach + duodenum), mixing and propulsion, digestion, absorption and defecation • arterial supply by abdominal aorta • venous drainage to IVC via portal system • lymphatic drainage into thoracic duct BIMA Anatomy SeriesStomach Abdomen & GI Anatomy Pt.1 BIMA Anatomy Series Stomach • J-shaped bag. Has Four anatomical region: Cardia, Fundus, Body and Pylorus. The margins are made up of the lesser and greater curvature. The most inferior part of the lesser curvature is known as the Angular notch (junction of the body and pyloric region) and the LC gives rise to the hepatogastric lig. Sphincters regulate the amount of food that enters the stomach. • 2 sphincters: 1. Inferior Oesophageal sphincter- Th11 2. Pyloric sphincter- controls the exit of the digested mixture from the stomach. Made of smooth muscle. A- Coeliac trunk- anastomosis… V- R & L gastric veins drain into the hepatic portal vein. N- ANS, Parasympathetic from Vagus and Sympathetic via coeliac plexus which receives supply from Th6-Th9 segments. BIMA Anatomy SeriesStomach BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSmall Intestine Abdomen & GI Anatomy Pt.1 BIMA Anatomy SeriesSmall Intestine - Duodenum • C- shaped, around 25cm long and wraps around the head of the pancreas. • Superior/ cap part of the Duodenum (L1) from the pylorus, connected to liver by hepatoduodenal lig. • Descending (L1-L3) curves inferiorly around head of the pancreas, post. to transverse colon and ant. to R kidney and Vater’s • Inferior, travels laterally to the left, crossing the IVC & Aorta, post. to SMA. • Ascending (L3-L2), after it crosses the aorta, it ascends and curves anteriorly to join jejunum at a turn called the duodenojejunal flexure. At this flexure, is the suspensory muscle and lig. of the duodenum, contraction of the muscle widens the angle of the flexure and aids movement of intestinal contents into jejunum. BIMA Anatomy SeriesDuodenum BIMA Anatomy Series Small intestines BIMA Anatomy SeriesSmall Intestine – Jejunum & Ileum • In contrast to the duodenum, are intraperitoneal, attached to posterior abdominal wall by Mesentery. • 6m/ 20 ft long, Jejunum is 8ft and Ileum is 12 ft. • Jejunum starts at DJ flexure and there is not clear demarcation point between J & I (only via histology). Ileum terminates at Ileocaecal valve. At this point, the Ileum invaginates into caecum. Cannot propagate food contents forward but can prevent reflux. BIMA Anatomy SeriesSmall Intestine – Differences? BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesLiver Abdomen & GI Anatomy Pt.1 BIMA Anatomy Series Liver • Produces bile and has lots of metabolic functions. • Biggest gland in the body, 1.5 kg, located in the right upper quadrant. • Posteriorly, RL is related to the R Kidney (Renal impression), R Suprarenal gland (Suprarenal impression), descending part of the duodenum (duodenal impression), right colic flexure (colic impression) and the LL is related to the oesophagus (oesophageal impression) and stomach (gastric impression). • Fibrous capsule, hepatic lobules each with a small central vein. Functional unit is rather the portal acinus. Blood flow V: Portal vein A: Proper Hepatic artery BIMA Anatomy SeriesLiver BIMA Anatomy Series Liver cont. • Diaphragmatic surface: 1. superior part – mostly fuses with the diaphragm, bare area defines the coronary ligament that continues to the right triangular and left triangular lig, terminates as the fibrous appendix. 2. Anterior part – covered by peritoneum, divided by the falciform lig into the right and left lobe. • Visceral surface : in the shape of an H 1. Right sagittal fissure- posteriorly the groove of the IVC, fixed by a fibrous band (VC lig), anteriorly is the fossa of the GB. 2. Left sagittal fissure- posteriorly venous lig- occluded venous duct, anteriorly the round ligament of the liver- occluded umbilical vein. • Segments… BIMA Anatomy SeriesBIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotterSpotterSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesPeritoneum Abdomen & GI Anatomy Pt.1 BIMA Anatomy Series Peritoneum • Thin serous membrane which consists of a single layer of flattened cells (mesothelium). • Parietal peritoneum, which lines the walls of the abdominal and pelvic cavities. • Visceral peritoneum, which covers the organs. • Greater sac, which is the main component of the peritoneal cavity whereas the lesser sac is a small diverticulum from the greater sac with which it communicates via the epiploic foramen of Winslow. It lies behind the stomach and is called the Omental bursa sometimes. BIMA Anatomy SeriesPeritoneum BIMA Anatomy SeriesPeritoneum BIMA Anatomy SeriesPeritoneum BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesColon Abdomen & GI Anatomy Pt.1 BIMA Anatomy Series Colon • 150cm in length, from proximal to distal: ascending, transverse, descending and sigmoid. • Ascending colon is retroperitoneal, meets the right lobe of the liver and turns 90 degrees to move horizontally (R Colic flexure/ Hepatic flexure). This is the start of the transverse colon. • TC extends to spleen where it turns another 90 degrees to point inferiorly ( L Colic flexure/ Splenic flexure). Here the colon is attached to diaphragm by the phrenicocolic lig. It is the least fixed part of the colon. Is intraperitoneal and enclosed by transverse mesocolon. • DC, after LCF, the colon moves inferiorly towards the pelvis. Retroperitoneal. Located anteriorly to the L kidney, when it turns medially, becomes sigmoid colon. • Sigmoid is 40cm and in the LIQ. Extends from LIF to S3, this gives it the ”S” shape. Attached to the posterior pelvic wall by a mesentery known as the Sigmoid mesocolon. BIMA Anatomy SeriesColon BIMA Anatomy SeriesColon BIMA Anatomy SeriesSpotter BIMA Anatomy SeriesSpotter BIMA Anatomy Series Rectum • Temporary storage for faeces. Proximal to sigmoid colon and terminates into the anal canal. Begins at S3, macroscopically different from the colon and final segment is the Ampulla, is continuous with the anal canal. • Course of the rectum is marked by two major flexures: - Sacral, AP curve with concavity anteriorly (follows curve of sacrum and coccyx). - Anorectal flexure, AP curve with convexity anteriorly. Formed by tone of puborectalis muscle. • Sup. 1/3 , ant. And lateral surfaces covered by peritoneum. Middle 1/3 rd has only rd anterior covering and lower 1/3 has none. • Reflections of peritoneum from rectum to posterior walls form pouches. A- sup. Rectal (IMA), mid. Rectal (IIA) and inf. Rectal (int. pudendal) V- corresponding veins as like arteries. Portocaval anastomosis. N- Symp from lumbar splanchnic nerves & sup. and inf. Hypogastric plexuses. Para from pelvic splanchnic nerves and inferior hypogastric plexuses. Visceral afferent sensory fibres follow para supply. BIMA Anatomy SeriesRectum BIMA Anatomy Series Rectum relations BIMA Anatomy Series Anal canal • Final segment of GIT. Important role in defecation and mainting faecal continence. Begins as a continuation of the rectum and passes inferoposteriorly to terminate at the anus. • Sphincters: rd 1. Internal- surrounds upper 2/3 of anal canal. Formed by thickening of the involuntary circular smooth muscle in bowel wall. 2. External- voluntary muscle that surrounds lower 1/3 of the canal and overlaps with internal sphincter. Also blends superiorly with the puborectalis muscle of the pelvic floor. • At junction of rectum and anal canal there is a muscular ring, known as the anorectal ring (felt on DRE). Formed by fusion of internal, external sphincters and puborectalis muscle. • The columns are joined together at their inferior ends by anal valves. Above valves are small pouches known as anal sinuses (secrete mucus). The valves collectively form an irregular circle known as the Pectinate line/ Dentate line which divides the anal canal into upper and lower parts, which differ in structure, origin and neurovascular supply. BIMA Anatomy SeriesAnal canal BIMA Anatomy Series Final thoughts? BIMA Anatomy SeriesReferences All cadaveric images: https://sites.google.com/a/umich.edu/bluelink/resources/bluelink Theory: https://teachmeanatomy.info/ BD. Chaurasia’s Human Anatomy, 6 edition st MRCS System Modules: Essential Revision Notes, 1 edition. BIMA Anatomy SeriesTHANK YOU