Abdomen – 1

Human Structure and Development 212Week 6 – 2005

Avinash Bharadwaj

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

• Mucosa• 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

• 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

• 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

• 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

Peritoneal connections• 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

Liver

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”.