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Abdomen – 1
Human Structure and Development 212
Week 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
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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
Liver
 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
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”.