Human Structure and Development 212 Abdomen 1 Abdomen – 1 Human Structure and Development 212 Week 6 – 2005 Avinash Bharadwaj 212-Wk5 L1 - avb 2005

Regions of Abdomen Descriptive convenience Landmarks used Midclavicular lines (planes) Transpyloric and transtubercular planes Variation in descriptions Epigastrium, umbilical, hypogastrium Two each – hypochondrium, lumbar, iliac

Peritoneum Highly complex cavity, especially in the upper abdomen. Essential concepts Visceral and parietal layers Mesenteries (The mesentery, mesogastrium, mesocolon etc) Retroperitoneal structures Greater and lesser sacs

Peritoneum Lesser sac Greater sac Greater omentum Lesser omentum The mesentery –Small intestine Mesocolon – Transverse + sigmoid

Retroperitoneal Structures Organs which lose their mesentery Secondarily retroperitoneal Duodenum, pancreas, ascending colon, descending colon Organs which develop posterior to the cavity Primarily retroperitoneal Kidneys, adrenals

GI Tract – General Plan Four layers Submucosa Muscularis externa Lining epithelium + Lamina propria Muscle layer – muscularis mucosae Submucosa Main connective tissue layer Major network of blood vessels Network of nerves Muscularis externa Smooth muscle Inner circular Outer longitudinal Serosa or adventitia

Stomach Curvatures – variability in shape Parts Fundus, body, pyloric antrum and canal Functional divisions more important! Interior – rugae (Folds) Sphincters : “gate mechanisms” Functional Anatomical – thickening of circular muscle What type are the sphincters of the stomach?

Small Intestine Absorptive function Duodenum Jejunum and ileum Large surface area Circular folds of mucosa Villi – projections of epithelium Duodenum Largely retroperitoneal, C-shaped Openings of bile and pancreatic ducts Jejunum and ileum Long, with mesentery Gradual transition Thinner wall, smaller folds and villi, pattern of blood vessels

Colon General features Caecum + appendix Haustration Taeniae coli – three bands of longitudinal muscle Caecum + appendix Vermiform appendix Importance and positions Ascending, transverse and descending parts Location, peritoneal covering Flexures – hepatic and splenic Variability

Pattern of Blood Vessels Three major arteries Coeliac Superior mesenteric Inferior mesenteric Branches and anastomoses Long channels parallel to gut tube Short straight vessels Submucosa – rich network

Liver Largest gland in the body Functions Anatomical perspective Production of bile Metabolic functions – carbohydrates, amino acids Protein synthesis Breakdown of haemoglobin And many others…! Anatomical perspective

Liver Receives venous blood from abdominal GIT Portal vein Arterial blood supply – hepatic artery Hepatic veins – venous drainage to IVC Porta hepatis – the gateway Hepatic artery, portal vein, bile ducts One each from right and left ‘lobes’ Functional lobes more important! Anatomical lobes by landmarks

Liver Peritoneal connections Diaphragmatic surface Falciform ligament Lesser omentum Diaphragmatic surface “Visceral” surface Details of relations not necessary Ligamentum teres Obliterated umbilical vein Umbilical vein – blood from the placenta Ligamentum venosum Obliterated ductus venosus Ductus venosus – shunt between portal vein and IVC

Portal Vein IMV  Splenic SMV + Splenic  Portal vein Joined by smaller veins from stomach etc

Portasystemic anastomoses Junctional regions Oesophagus  systemic veins to thorax, stomach  portal vein Anal canal (terminal part  systemic) Other regions “Bare area” of liver Around the umbilicus Around retroperitoneal organs Liver disease especially “cirrhosis” Portal hypertension  “varicosity”.