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Anatomy T eaching Session 5 Gastrointestinal Anatomy and Radiology The focus of this presentation is on GI anatomy revision through the context of basic radiology Aims and Objectives Abdominal Cavity • Describe the location of the stomach in the abdomen. • Identify the key landmarks that are visible or palpable on examination of the abdomen. • Describe the anatomical relations of the stomach. • Describe the four quadrants and nine regions of the abdomen and name the major organs that are • Know the arterial supply and venous drainage of the stomach. located deep to these regions. • Know the innervation of the stomach. • Describe the anatomy and function of the anterior abdominal wall muscles. • Identify the location and borders of the inguinal canal. Intestines • Describe the parts of the small and large intestine. Abdominal Viscera • Describe the location of the small and large intestine in the abdomen. • Identify the major organs within the abdominal cavity. • Describe the anatomical relations of the small and large intestine. • Describe the parietal and visceral peritoneum and the peritoneal cavity. Describe the innervation of the parietal and visceral peritoneum and its clinical significance. • Know the arterial supply and venous drainage of the small and large intestine. • Explain the terms ‘intraperitoneal’ and ‘retroperitoneal’ and give examples of intraperitoneal and • Know the innervation of the small and large intestine. retroperitoneal structures. • Understand the terms ‘mesentery’ and ‘omentum’. Understand their functions. Radiological Context • Describe and identify the abdominal viscera on an X-ray or a CT-Scan. Upper GI Tract • Understand how Radiology techniques are used to detect bowel conditions. • Describe the anatomy of the distal oesophagus. • Describe the anatomy of the parts of the stomach. The focus of this presentation is on GI anatomy revision through the context of basic radiology Disclaimer The following presentation has been made for medical students by medical students, therefore focus is on anatomy revision through the context of basic radiology. This is a learning tool that has not been reviewed by the University of Sheffield and therefore the use of this session is to facilitate your learning only. We are not accountable for any inaccuracies. The focus of this presentation is on GI anatomy revision through the context of basic radiology The Abdominal Cavity – Surface Anatomy • Abdominal cavity defined by palpable bony landmarks • Upper boundary (borders thorax) • Xiphisternum • Costal margin • Lower boundary (borders pelvis) • Iliac crests (palpable posteriorly) • Anterior superior iliac spines • Pubic tubercles • Other landmarks • Umbilicus • Linea alba The fthrough the context of basic radiologytomy revisionThe Abdominal Cavity – Surface Anatomy • The abdomen can be divided into discrete areas, separated by anatomical lines • Two major divisions: Four Quadrants Nine Regions Vertical Vertical Midline Midclavicular lines Horizontal Horizontal Transumbilical plane Subcostal Intertubercular 1 2 3 4 5 6 7 8 9The Abdominal Cavity – The Anterolateral Abdominal Wall • Abdominal walls composed of: • Skin • Superficial fascia • Muscles and aponeuroses • Parietal peritoneum • Different tissues work together to: • Protect abdominal viscera and maintain their position • Maintain posture • Increase intra-abdominal pressure (coughing, vomiting, childbirth and defecation) The through the context of basic radiologyatomy revisionThe Abdominal Cavity – The Anterolateral Abdominal Wall 1 2 4 3 The fthrough the context of basic radiologytomy revisionThe Abdominal Cavity – The Anterolateral Abdominal Wall The focus of this presentation is on GI anatomy revision through the context of basic radiologyThe Abdominal Cavity – The Anterolateral Abdominal Wall The focus of this presentation is on GI anatomy revision through the context of basic radiologyThe Abdominal Cavity – The Inguinal Canal • Inferomedial passage that crosses inferior part of the anterior abdominal wall • Runs parallel to medial half of the inguinal ligament • Extends from deep inguinal ring laterally to superficial inguinal ring medially Anterior Border Posterior Border Roof Floor Aponeurosis of the Transversalis fascia Transversalis fascia Inguinal ligament external oblique Medial fibres of the Internal oblique Laterally: internal internal oblique oblique and transversus Transversus abdominis abdominis aponeuroses (conjoint tendon) The fothrough the context of basic radiologyomy revisionThe focus of this presentation is on GI anatomy revision through the context of basic radiologyThe focus of this presentation is on GI anatomy revision through the context of basic radiology2003 The focus of this presentation is on GI anatomy revision through the context of basic radiologyAbdominal Viscera – Nine Regions Right hypochondriac Epigastric Left hypochondriac Liver Stomach Liver (tip) Gallbladder Liver Stomach Right kidney Pancreas Pancreas Small intestine Spleen Left Kidney Adrenal glands Spleen Duodenum Large/small intestine Right lumbar Umbilical Left lumbar Ascending colon Duodenum Descending colon Small intestine Small intestine Small intestine Right kidney Transverse colon Left kidney Right iliac Hypogastric/Suprapubic Left iliac Appendix Bladder Sigmoid colon Cecum Sigmoid colon Descending colon Ascending colon Small intestine Small intestine Small intestine Reproductive organsAbdominal Viscera - Imaging 2 1 3 4 10 9 5 8 7 6 The fthrough the context of basic radiologytomy revisionAbdominal Viscera - Peritoneum • Two continuous layers of connective tissue lined by mesothelium • Parietal peritoneum = lines internal surface of abdominopelvic wall • Visceral peritoneum = covers abdominal viscera • Peritoneal layers are separated by a cavity lined by 50-100mL fluid for lubrication • Pain is felt differently in both peritoneal layers. Why? • Parietal peritoneum is innervated by the same somatic nerves that innervate overlying muscles and skin. Sharp, severe and well localised. • Visceral peritoneum is innervated by the same visceral nerves that innervate underlying abdominal viscera. Dull and diffuse. The through the context of basic radiologyatomy revisionAbdominal Viscera – Peritoneal Problems The focusthrough the context of basic radiology revisionAbdominal Viscera – Retroperitoneal Viscera Suprarenal (adrenal) glands Aorta and IVC Duodenum Pancreas (except tail) Ureter Colon Kidney Esophagus Rectum The focus of this presentation is on GI anatomy revision through the context of basic radiologyAbdominal Viscera – Mesentery/Omenta • Peritoneum facilities neurovascular supply to viscera within • Achieves this through several peritoneal reflections and folds Mesentery Omentum Principle organ involved Small (and parts of large) Stomach intestine Duodenum Connections Posterior abdominal wall Small intestine Transverse colon Liver • Omenta divided into • Greater omentum (4 peritoneal layers) = connects greater curvature of stomach to small intestine • Lesser omentum (2 peritoneal layers) = connects lesser curvature of stomach and duodenum to the liverAbdominal Viscera – Blood Supply Coeliac trunk at T12. SMA at L1 IMA at L3 Renal artery L1 Common exam question The fthrough the context of basic radiologytomy revisionUpper GI T ract – The Distal Oesophagus • Crosses diaphragm at oesophageal hiatus • Spinal level = T10 • Oesophageal hiatus is an area of anatomic constriction -> food is likely to be impacted • Muscle fibres surrounding hiatus constitute the lower oesophageal sphincter • Functional sphincter -> opening dictated by surrounding muscle contraction • Arterial supply: left gastric artery • Venous drainage: oesophageal veins (systemic) and portal veins • Nerve supply: Vagus nerve (CNX) (parasympathetic) and sympathetic trunk fibres (sympathetic) Common exam questions!! The focus of this presentation is on GI anatomy revision through the context of basic radiologyUpper GI T ract – Barium Swallow • Barium marker used to visualise upper GI tract • Look for sizes and abnormalities in the organs constituting the tract • Can also visualise the swallowing process • Process 1. Fasting for approx. 8 hours prior 2. Swallowing barium drink 3. Series of X-rays, or fluoroscopy, taken to track progression of the drink down the GI tract 4. RepeatUpper GI T ract – Parts of the Stomach 2 1 3 9 10 8 7 4 5 6 The fthrough the context of basic radiologytomy revisionUpper GI T ract – Position of the Stomach • Primarily in left upper quadrant, but spans over multiple regions • Intraperitoneal • Anterior surface = diaphragm, left lobe of the liver and anterior abdominal wall • Posterior surface = pancreas The focus of this presentation is on GI anatomy revision through the context of basic radiologyUpper GI T ract – Neurovascular Supply of the Stomach • Which major abdominal artery supplies the stomach? The coeliac trunk • Anastomoses run along both curvatures of the stomach • Greater curvature = right and left gastro-omental arteries • Lesser curvature = right and left gastric arteries • Venous drainage: gastric and gastro-omental veins • Ultimately drain into hepatic portal vein • Innervation: Vagus nerve (CNX) parasympathetic and greater splanchnic nerve The focus of this presentation is on GI anatomy revision through the context of basic radiologyIntestines – Coronal Plane CT 1 1 2 2 3 3 4 4 5 5 6 6 7 7Small Intestine - Overview 1 2 3 5 4 6 7 The fthrough the context of basic radiologytomy revisionSmall Intestine - Duodenum • What is the major duodenal papilla? Opening of bile duct • Arterial supply • First half of the duodenum: branches of the coeliac trunk • Second half of the duodenum: branches of the superior mesenteric artery • Why the difference? The through the context of basic radiologyatomy revision Small Intestine – Jejunum and Ileum • Long and folded for large surface area • Folded mucosa = pilcae circulares • Villi and microvilli Jejunum Ileum More prominent Less numerous Pilcae circulares and pronounced No Yes Peyer’s patches? The fothrough the context of basic radiologyomy revisionSmall Intestine – Superior Mesenteric Artery • SMA leaves aorta at L1 • Splits into approximately 20 anastomosing branches called arcades • Arcades project straight arteries, called vasa recta, which supply intestinal wall • Branches are embedded in the mesentery of the small intestine • Relevant branches of the SMA that supply the small intestine: • Jejunal branches • Ileal branches • Ileocolic artery The fthrough the context of basic radiologytomy revisionLarge Intestine - Overview The focusthrough the context of basic radiology revisionLarge Intestine – Internal Anatomy The focusthrough the context of basic radiology revisionLarge Intestine – X RayLarge Intestine – X Ray Haustral Folds >6cm Haustral Folds Babu,Radiopaedia.org,rID: 18015Ultrasound • Is this high contrast? • No • Why don’t we use ultrasounds to look for deep abnormalities? • Because it can only offer insights about superficial structures. The fthrough the context of basic radiologytomy revision Case 1 Patient Presentation: Mr. John Doe, a 54-year-old male, presents with severe abdominal pain and bloating for the past two days. He reports nausea, vomiting, and inability to pass stools or gas. His last normal bowel movement was four days ago. He has a history of hypertension and an appendectomy at age 24. Physical Examination: The patient appears unwell, with tachycardia (112 bpm) and a mildly elevated temperature (37.8°C). His abdomen is distended with visible peristalsis and tenderness, particularly in the lower quadrants. Bowel sounds were initially hyperactive but have diminished. A rectal exam reveals an empty rectal vault with no blood. An abdominal X-ray is performed, showing dilated small bowel loops with air-fluid levels and a "step-ladder" pattern. There is no free air under the diaphragm, ruling out perforation. Review Questions: What could the diagnosis be? What are other possible causes of bowel obstruction in this patient? Why didn’t we go for a CT scan initially? The focus of this presentation is on GI anatomy revision through the context of basic radiologyAnswer Diagnosis: The findings suggest a small bowel obstruction (SBO), most likely due to adhesions from the patient’s prior appendectomy. A CT scan reveals dilated small bowel loops proximal to a transition point in the mid-ileum, with collapsed bowel distally. There is no bowel wall thickening or signs of perforation, supporting the diagnosis of SBO without ischemia. Management: The patient is managed conservatively with IV fluids, nasogastric tube decompression, and bowel rest (NPO). Surgical consultation is advised in case of worsening symptoms or ischemia. The focus of this presentation is on GI anatomy revision through the context of basic radiologyAnswer • What are other possible causes of bowel obstruction in this patient? • Hernias: An external or internal hernia could trap bowel loops, causing obstruction. • Neoplasms: A tumour within the bowel or compressing it externally can lead to blockage. • Inflammatory Bowel Diseases: Conditions like Crohn’s disease may cause strictures that obstruct the bowel. • Foreign Bodies or Bezoars: Swallowed objects or masses of indigestible material can obstruct the lumen. • Volvulus: Twisting of the bowel on its mesentery, commonly involving the sigmoid colon or cecum, can obstruct blood flow and the lumen. • Infections: Severe infections, such as tuberculosis, may cause bowel obstruction via strictures or inflammatory masses. The focus of this presentation is on GI anatomy revision through the context of basic radiologyA patient is admitted to the hospital with an abdominal pain in their right upper quadrant. Which of the organs is located there? • A) Liver • B) Caecum • C) Descending colon • E) Ileum The focthrough the context of basic radiologymy revisionA patient is admitted to the hospital with an abdominal pain in their right upper quadrant. Which of the organs is located there? • A) Liver • B) Caecum RLQ • C) Descending colon LLQ • E) Ileum RLQ The focthrough the context of basic radiologymy revisionA patient had an aneurysm from one of the unpaired arteries that branches from the abdominal aorta at level of T12. Which one is more likely to be affected? • A) Superior mesenteric artery • B) Inferior mesenteric artery • C) Coeliac trunk • D) Renal artery The focthrough the context of basic radiologymy revisionA patient had an aneurysm from one of the unpaired arteries that branches from the abdominal aorta at level of T12. Which one is more likely to be affected? • A) Superior mesenteric artery L1 • B) Inferior mesenteric artery L3 • C) Coeliac trunk T12 • D) Renal artery L1 The focthrough the context of basic radiologymy revisionA medical student is dissecting the abdominal cavity. Which of the following will help them identify the small intestine? • A) Haustra • B) Plicae circulares • C) Epiploic appendages • D) Taeniae coli The focus of this presentation is on GI anatomy revision through the context of basic radiologyA medical student is dissecting the abdominal cavity. Which of the following will help them identify the small intestine? • A) Haustra • B) Plicae circulares • C) Epiploic appendages • D) Taeniae coli The focus of this presentation is on GI anatomy revision through the context of basic radiologyPouria, a 35-year-old male, has many organs. Which of the following are retroperitoneal? • A) Stomach • B) Tail of the pancreas • C) Aorta • D) Liver The focus of this presentation is on GI anatomy revision through the context of basic radiologyPouria, a 35-year-old male, has many organs. Which of the following are retroperitoneal? • A) Stomach • B) Tail of the pancreas • C) Aorta • D) Liver The focus of this presentation is on GI anatomy revision through the context of basic radiologyThanks for Listening! Session 5 psanikhani1@sheffield.ac.ukReferences • Anatomy handbook. University of Sheffield. School of medicine and population health. Gastrointestinal anatomy. • https://teachmeanatomy.info/ • https://www.radiologyinfo.org/en/info/abdominct • https://www.radiologycafe.com/radiology-basics/abdomen/abdomen-anatomy/ • https://www.radiologycafe.com/radiology-basics/abdomen/abdomen-anatomy/ • https://radiopaedia.org/articles/small-bowel-obstruction?lang=gb • https://med.emory.edu/departments/emergency-medicine/sections/ultrasound/case-of-the-month/abdominal/small_bowel_obstruction1.html • https://geekymedics.com/abdominal-aorta/ • The rest are in the footnotes.