T1 L1: Introduction to the peritoneal cavity

• Accessory organs of the gastrointestinal system

  • Liver
  • gallbladder
  • pancreas
• Parts of the small intestine

  • duodenum
  • jejunum
  • ileum
• Parts of the large intestine

  • caecum and appendix
  • ascending colon
  • transverse colon
  • descending colon
  • sigmoid colon
  • anal canal
• Foregut made of?

  • oesophagus
  • stomach
  • duodenum (part)
  • liver and biliary system
  • pancreas

  
• Midgut made of?

  • duodenum (part)
  • Jejunum
  • Ileum
  • caecum and appendix
  • ascending colon
  • proximal 2/3rds transverse colon

  
• Hindgut made of?

  • distal 1/3rd of transverse colon
  • descending colon
  • sigmoid colon
  • rectum
  • anal canal

  
• Organs of the endocrine system?

  • spleen
  • suprarenal (adrenal) gland

  
• Organs of the urinary system?

  • kidney
  • ureter
  • bladder

  
• Peritoneum 


  A thin, serous membrane lining the abdominal and pelvic cavities
• 2 types of peritoneum

  1. Parietal peritoneum: lines the walls of the abdominal and pelvic cavities
  2. Sensitive to pain, temperature, touch, pressure
  3. Innervated by T7-L1
  4. Normally well localised
  5. Visceral peritoneum: lines the abdominal and pelvic organs
  6. Sensitive to stretch, chemical irritation
  7. Innervated by afferent nerves that travel with autonomic supply to viscera
  8. Poorly localised
• Peritoneal cavity

  • a potential space between parietal and visceral peritoneum
  • contains peritoneal fluid
  • 'closed' cavity in males
  • communication with exterior via uterine tubes in females
  • mucous plug in external os (cervix) protect female peritoneal cavity from pathogens

  
• Intraperitoneal relationship

  • organs are completely covered with visceral peritoneum
  • organs are attached to each other/abdominal wall by a double fold of peritoneum of:
  • mesentry
  • ligaments
  • omentum
  • organs have greater mobility.

  
• Extraperitoneal relationship

  • organs are partially or entirely devoid of peritoneum
  • according to position can be:
  • Retroperitoneal (behind peritoneum, back of abdominal wall)
  • Subperitoneal (below peritoneum)
  • organs slightly movable or immovable

  
• Peritoneal relationships

  1. Intraperitoneal (organs completely covered with visceral peritoneum)
  2. Extraperitoneal (organs partially or entirely devoid of peritoneum)
  3. Retroperitoneal (behind peritoneum)
  4. Subperitoneal (below peritoneum)

  
• Peritoneal adhesions

  • pathological bonds between parts of peritoneum
  • can occur after infections, operations or damage
  • limit normal movement of viscera; can cause chronic pain, intestinal obstruction, difficulties with reoperative surgery

  
• Primary vs Secondary Retroperitoneal

  Primary - organs develop behind the peritoneum

  Secondary - organs begin as intraperitoneal but migrate behind peritoneum during development
• Retroperitoneal Organs (PEAR DUCK) (*= secondary retroperitoneal)


  • Pancreas* (apart from tail)
  • Esophagus (abdominal)
  • Aorta + IVC
  • Rectum (middle 1/3rd)
  • Duodenum* (distal)
  • Ureters (proximal)
  • Colon (ascending & descending*)
  • Kidneys
  • Suprarenal glands

  
• Intraperitoneal organs


  • stomach
  • liver
  • spleen
  • tail of pancreas
  • duodenum (proximal 2cm)
  • jejunum
  • ileum
  • caecum
  • appendix
  • transverse colon
  • sigmoid colon
  • rectum (upper 1/3rd)
  • ovaries
• Subperitoneal organs


  • rectum (lower 1/3rd)
  • urinary bladder
  • distal ureters
  • uterus
  • uterine tubes
• Peritoneal Folds

  • Mesentery: double layer of peritoneum that connects organs to body wall & gives pathway to blood vessels, nerves and lymphatics from posterior abdominal wall to organ
  • Omentum: double/quadruple layer of peritoneum from stomach/proximal duodenum to adjacent organs (lesser omentum and greater omentum)
  • Peritoneal ligament: double layer of peritoneum that connects an organ with another organ/body wall

  
• Fill in the blanks

  1 and 2. Intraperitoneal organ

  3. Subperitoneal organ

  4. Omentum (lesser)

  5. Retroperitoneal organ

  6. Mesentery

  7. Parietal peritoneum

  8. Peritoneal cavity

  
• Formation of the gut tube

  • folding occurs in 2 planes: cephalocaudal and lateral
  • this transforms embryo from a flat disc to a three dimensional vertebrate body form
  • gut tube develops from endoderm
  • peritoneum and mesentery form mesoderm

  
• The gut tube

  • Foregut: blind ending tube until week 4-5 when oropharyngeal membrane ruptures to form the mouth
  • Midgut: remains in communication with yolk sac via the vitelline duct until 14-20 weeks
  • Hindgut: cloacal membrane ruptures by end of week 7 to form urogenital and anal openings

  
• Lesser sac

  • lies behind stomach and lesser omentum
  • Epiploic foramen is the conduit between greater and lesser sacs

  
• Formation of the Greater omentum

  inferiorly, dorsal mesentery of the stomach enlarges in an inferior direction to form it

  fuses with the mesentery of the transverse colon to form an apron-like structure

  
• Greater Omentum

  • forms adhesions adjacent to inflamed organ to limit spread of infection and isolate wounds
  • Contains high volume of fat:
  • cushions organs
  • insulation against loss of body heat

  
• Midgut rotation weeks 5-10

  1. Tube initially as long as developing body - grows rapidly to provide surface required for nutrition
  2. Rate of growth outpaces development of space within the trunk. Midgut extends into proximal part of umbilical cord
  3. Once there is room, midgut returns to the abdominal cavity. In total, midgut rotates 270 degrees.
  4. As parts of the gut tube reach their final positions, their mesenteric attachments undergo modification (some shorten/disappear).

  
• Malrotation of the gut

  Can be asymptomatic, cause intermittent symptoms of intestinal obstruction, or can lead to development of a volvulus.

  Volvulus - a complete twisting of a loop of intestine around its mesenteric attachment site

  
• Root of the mesentery (of the small intestine)

  • extends from the duodenojejunal flexure
  • to the ileocaecal junction

  
• Subdivisions of the peritoneal cavity

  • Greater Sac - everything else
  • Supracolic
  • Infracolic - sub divisions divided by paracolic gutters
  • Right infracolic
  • Left infracolic
  • Lesser Sac - behind stomach

  
• Flow of ascitic fluid and pus

  • paracolic gutters provide pathways for flow of ascitic fluid and spread of infection from abdominal cavity into pelvic cavity
  • patients with peritonitis often placed at at least 45 degree angle to promote flow into pelvis and avoid spread of infection