Peritoneum

• Peritoneum

  Serous membrane lining abdominal cavity and part of pelvic cavity
• Histologically is it divided into:

  • outer layer of fibrous tissue: gives strength to membrane
  • Inner layer of mesothelial cells: secrete serous fluid that lubrificates surface and allows for movements of vicera
• • Periteneum is in the form of a closed sac which is invaginated by number of vicera. As result peritoneum is divided into

  Outer parietal layer

  Inner viceral layer

  Folds of peritoneum that suspends vicera
• Peritoneum is s complete closed sac that lines abdominal walk (parietal) and becomes continuous snd reflected around abdominal organs (viceral), except in female, peritoneum is not closed, it opens into the free ends of uterine tubes, vagina.
• Parietal peritoneum

  • outer layer of peritoneum
  • Lines inner surface of abdominal wall mad pelvic wall
  • Composed if fibrous layer continous with transversalis fascia and serous layer that produce lubricant fluid that lubrificates peritoneal cavity allowing viceral and parietal layers to slide smoothly over each other.
  • Sensitive to pain, temperature and mechanical stimulus due to its somatic innervation

  
• Viceral peritoneum

  • Inner layer mesothelial cells that covers external surface of most abdominal organs (liver, stomach, spleen)
  • Reflects off the organ to become continuous with parietal peritoneum creating a closed sac
  • Single layer of mesothelial cells + CT
  • Insensitive to pain, supplied by autonomic nerves

  
• Peritoneal cavity

  • Potential space btw parietal and viceral peritoneum
  • Contains thin layer of serous fluid:lubrificates
  • Closed in males but open in females
  • Divided into various compartments by peritoneal folds and ligaments which helps support and organise abdominal organs
  • Broadly divided into greater and lesser sac(omental bursa). The sac communicates with each other through epiploic foramen (T12)

  
• Peritoneal folds

  Double layer of peritoneum that extends from abdominal wall to organs or btw organs.

  • Provide support to organs
  • Contains blood vessels, nerve, lymphatics
  • Suspend: provide mobility to vicera
• Classification of peritoneal folds

  1. Mesenteries: double layer of peritoneum that anchor vicera to posterior abdominal wall.

  Mecolon: fold of peritoneum that attaches colon to posterior abdominal wall /Sigmoid mesocolon: sigmoid colon to posterior abdominal wall/transverse mesocolon.

  2. Omenta: peritoneal fold that connects stomach to other organs. Greater omentum (stomach with transverse colon)/ lesser omentum ( lesser curvature + proximal duodenum to liver. Includes hepatogastric and hepatoduodenal lig. Contains portal vein, hepatic artery and bile duct)

  
• Intraperitoneal organs

  • Completely surronded by peritoneum and are suspended within peritoneal cavity by mesentery or mesentery like structures (liver, stomach, spleen, transverse+ sigmoid colon, jejunum, ileum
• Retroperitoneal organs

  • Partially covered with peritoneum

  2 types:

  1. Retroperitoneal: peritoneum only on ant suf. lies btw peritoneum and posterior abdominal wall. Are immobile (ascending + descending colon, adrenal gland, pancreas except tail, kidney, urethra, rectum,duodenum except ampulla)
  2. Subperitoneal: peritoneum only on sup suf (urinary bladder, porstate, seminal vesicles, uterus)

  
• Peritoneum in transverse section

  
• Greater sac

  • main and larger part of peritoneal cavoty
  • Extends from diaphragm to pelvis and includes most of peritoneal cavity.

  Subdivided into supracolic and infracolic

  • Supracolic: above transverse mesocolon. Contains stomach, liver and spleen
  • Infracolic: below transverse mesocolon, contains small intestine n parts of large intestine. Futher divided by mesentery of small intestine into right and left infracolic spaces

  
• Right and left infracolic sapces

  • Right infracolic space: triangular
  • Left infracolic space: larger and quadrangular

  
• Lesser sac

  • Aka omental bursa, smaller subdivision of peritoneal cavity.
  • Situated posterior to stomach and lesser omentum and provides space where stomach can expand and move during digestion
  • Communicates with greater sac through epiploic foramen.

  
• Epiploic foramen

  • Natural opening that connects lesser sac to greater sac
  • Bordered anteriorly by hepatoduodenal ligament (portal triad) and posteriorly by inferior vena cava, superiorly by caudate lobe of liver and inferiorly by first part of duodenum

  
• • The pelvic peritoneal space in males includes: the rectovesical pouch : between rectum & urinary bladder
  • The pelvic peritoneal space in females includes :

  the rectouterine pouch (Douglas’s pouch) : between rectum & uterus and the vesicouterine pouch : between urinary bladder & uterus

  
• Pelvic peritoneum in males

  • Peritoneum descend to cover front and middle sides of rectum
  • Then it reflects anteriorly to cover upper poles of seminal vesicles and upper part of base of urinary bladder forming rectovesical pouch

  
• • In males
  • From rectum: peritoneum reflects laterally to side walls of pelvis forming right and left pararectal fossae
  • From upper suf of urinary bladder peritoneum extends laterally to side walks of pelvis forminh right and legt patavesical fossae
  • From upper suf of urinary bladder peritoneum extends forwards and upwards to lower part of anterior abdominal wall forming median umbilical fold, 2 medial umbilical folds and 2 lateral umbilical folds
• In females peritoneum covers front and sides of rectum→ reflects anteriorly to cover posterior fornix of vagina and posterior surface of uterus forming rectouterine pouch→then it covers fundus of uterus and anterior surface of uterus→reflects forwards to upper surface of urinary bladder forming vesicouterine pouch

  
• In females from rectum peritoneum extends forwards and upwards to lower part of posterior aspect of anterior abdominal wall as in males.

  • On each side peritoneum extends from anterior and posterior walls of uterus to side walls of pelvis forming the 2 broad ligaments.
  • The rectouterine folds correspond to sacrogenital fold in male and it extends from the sides of uterine cervix to sacrum.
• functions of peritoneum

  • Movement: reduced friction from movements (peristalsis and respiration)
  • Protection( contains phagocytes and lymphocytes which participates in immune reaction.
  • Absorption: mesothelial cells act as semipermanent membrane that permits water and electrolytes to diffuse straight to blood vessel
  • Storage of fat
  • healing and adhesion
• Intraperitoneal organs

  • Completely covered by peritoneum
  • mobile: These organs tend to have a greater degree of mobility within the abdominal cavity due to their suspension by mesenteries.
  • Stomach, superior part of duodenum, jejunum, ileum, appendix, transverse colon, sigmoid colon, supraampular part of rectum, spleen and ovaries
• Mesoperitoneal organs

  • Covered with peritoneum on 3 surfaces
  • liver, gallbladder, ascending part of duodenum, cecum, ascending colon, descending colon, ampular part of duodenum, urinary bladder, uterus
• retroperitoneal organs

  • Peritoneum only on anterior surface
  • located in retroperitoneal space
  • not movable at all
  • descending and horizontal parts of duodenum, anal canal, pancreas, kidneys, adrenal glands, ureters, urinary bladder, major vessels (aorta, inferior vena cava)