8 Peritoneal and GI development 1 Flashcards
What is the peritoneum?
Thin serous membrane that lines the walls of the abdominal & pelvic cavities & “clothes” the viscera (organs)
What is the parietal peritoneum?
Lines the walls of the abdominal and pelvic cavities
What is the visceral peritoneum?
Covers the viscera (organs)
What is the peritoneal cavity? What is it divided into?
- Potential space between the parietal and visceral peritoneum
- Divided into greater and lesser sacs
What is peritoneal fluid?
- Small amount of serous fluid that the peritoneum secretes
* Lubricates the surfaces of the peritoneum to allow distension and free movement between the viscera (organs)
What structures do the peritoneum form?
- Omenta (greater and lesser)
- Mesenteries
- Ligaments
What is the difference in the peritoneal cavities of males and females?
Clinical risk?
- In males, the peritoneum is a closed cavity
- In females, there is communication with the exterior through the uterine tubes, the uterus, and the vagina
• Risk - may allow the spread of infection from the exterior to inside the peritoneal cavity
Where is the extraperitoneal tissue (connective tissue) found?
Between the parietal peritoneum and the fascial lining of the abdomen and pelvic walls (transversalis fascia)
What does retroperitoneal mean?
Any structure outside the peritoneal cavity
How is the peritoneal cavity divided?
- Greater sac:
• Main compartment
• Extends from the diaphragm down into the pelvis - Lesser sac (omental bursa):
• Smaller and lies behind the stomach and lesser omentum
• Extends slightly into the greater omentum
What structures allows free communications between the greater and less omentum?
Epiploic foramen of Winslow
What is the function of the epiploic foramen (omental foreamen/ foramen of Winslow)?
The greater and lesser sacs are in free communication via epiploic foramen
What are the triad of vessels in the free border of the lesser omentum?
- Portal vein - posteriorly
- Hepatic artery proper - anteriorly to the left
- Common bile duct - anteriorly to the right
What is the greater omentum?
- Derived from dorsal mesentery
- Attached to greater curvature of stomach and 1st part of duodenum
- Descends like an apron anterior to the small intestine before ascending to the transverses colon
- Consists of a double layer of visceral peritoneum folded upon itself (descending and ascending parts) => 4 layers in total
- Contains fat overlying the transverse colon and much of the small intestine
What structure is the “Policeman of the abdomen”? Function?
- Greater omentum
* Drawn to diseased or perforated structures to seal them off
What is the lesser omentum?
• Derived from the ventral mesentery
• Passes from the lesser curvature of the stomach
& 1st part of duodenum to
the inferior border of the
liver
• It can be subdivided
into the hepatogastric & hepatoduodenal ligaments
What is the hepatoduodenal ligament?
The free edge of the lesser omentum containing the portal vein, hepatic artery proper & common bile duct
What are mesenteries?
- Derived from the dorsal mesentery
- Tissue formed by a double layer of visceral peritoneum
- Suspend the abdominal viscera (organs) from the posterior abdominal wall
- Conduits for blood vessels, nerves & lymphatics
Name the mesenteries in the abdomen
- Small intestine:
• The mesentery
2. Colon: • Ascending • Transverse • Descending • Sigmoid mesocolons
- Vermiform appendix:
• Mesoappendix - Rectum:
• Mesorectum
What is the The Mesentery? Where does base start? Which structures does it cross? How long? Contains branches of which structures?
- A fan shaped double-layered fold of peritoneum connecting the jejunum and ileum to the posterior abdominal wall
- Its base starts at L2 and pass obliquely downwards to just above the right sacroiliac joint
- It crosses the 3rd part of the duodenum, the aorta and IVC, the right gonadal vessels and right ureter
- ~20 cm long
- It contains branches of the SMA and SMV, with nerves and lymphatics
What are the anastomotic arcade differences between the jejunum and ileum?
• The SMA branches are a series of anastomotic arcades within The mesentery
- Jejunum:
• Has few arcades
• Long vasa recta - Ileum:
• Has many arcades
• Short vasa recta
Sigmoid mesocolon:
What is it?
Root?
Transmits which vessels?
- Double-layered fold of peritoneum that connects the sigmoid colon to the posterior abdominal wall.
- Root:
• In the left iliac fossa, crossing the bifurcation of the left common iliac vessels and the left ureter - Transmits:
• The sigmoid branches of the inferior mesenteric vessels plus nerves and lymphatics
As parts of the intestine’s move from being retroperitoneal to intraperitoneal, little folds of peritoneum may be raised or form little recesses such as the ___ recesses
Paraduodenal recesses
Transverse mesocolon:
Function?
Root?
Carries branches?
- Suspends the transverse colon from the posterior abdominal wall
- Root:
• Just inferior to the pancreas - Carries branches of the middle colic vessels
Transverse mesocolon divides the peritoneal cavity (greater sac) into which compartments?
- Supracolic
2. Infracolic
Which organs are contained in the supracolic compartments?
- Liver
- Gallbladder
- Stomach
- Spleen
Which organs are contained in the infracolic compartments?
- Jejunum
- Ileum
- Ascending and descending colon
How is the infra colic compartment divided into right and left halves?
By The mesentery with each half having a parabolic gutter
Name the peritoneal pouches, recesses, spaces and gutters present within the peritoneum?
- Hepatorenal recess (Morison’s pouch)
Pelvic peritoneal pouches:
- Rectovesical pouch
- Rectouterine pouch (of Douglas)
- Vesicouterine pouch
What is the hepatorenal recess (Morison’s pouch)? What may collect there?
- Rights posterior sub hepatic space
* Blood/ pus may collect here with the latter forming abscesses particularly if lying recumbent
What is the rectovesical pouch?
- In males
* Separates rectum from urinary bladder
What is the rectouterine pouch (of Douglas)?
- In females
* Separates the rectum from uterus
What is the vesicouterine pouch?
- In females
* Separates the urinary bladder from uterus
What is a peritoneal fold?
Reflection of peritoneum with more or less sharp borders
How are peritoneal folds formed?
Formed by peritoneum that covers blood vessels, duct and obliterated foetal vessels
Name the peritoneal folds visible on the parietal peritoneum on the interior of the anterior abdominal wall
- Median umbilical fold
- 2 medial umbilical folds
- 2 lateral umbilical folds
What is the median umbilical fold?
Embryological remnant of the urachus that extends from the urinary bladder to the umbilicus
What are the 2 medial umbilical folds?
Embryological remnant of the umbilical arteries extending from the internal iliac arteries to the umbilicus
What are the 2 lateral umbilical folds?
Raised by the inferior epigastric arteries extending from the deep inguinal rings on each side to the arcuate lines
What are the peritoneal ligaments?
2 layered folds of peritoneum that connect 2 organs together
Peritoneal ligaments in the liver?
Liver is connected to diaphragm by:
• falciform ligament
• coronary ligaments
• triangular ligaments (right and left)
What is an intraperitoneal organ?
When organ is almost totally covered with visceral peritoneum & is suspended within the peritoneal cavity by a mesentery
What is a retroperitoneal organ? And the types?
• Lie behind or outside the peritoneum are only partially covered with visceral peritoneum
- Primary - always retroperitoneal
- Secondary - initially intraperitoneal but migrate retroperitoneally during embryogenesis and lose their mesentery
What organ has absorbed its peritoneal covering and is truly intraperitoneal?
Ovary
Which organs are primary retroperitoneal?
1. Urinary: • Suprarenal/ adrenal glands • Kidneys • Ureters • Bladder
- Circulatory:
• Abdominal aorta
• Inferior vena cava - Digestive:
• Oesophagus (final part)
• Rectum (middle 1/3 with lower 1/3 totally extraperitoneal)
Which organs are secondary retroperitoneal?
- Head, neck and body of pancreas (NOT tail - located in splenorenal/ lienorenal ligament)
- Duodenum (NOT proximal 1st part - intraperitoneal)
- Ascending and descending colon (NOT transverse or sigmoid colons)
Describe the nerve supply to parietal peritoneum:
• Sensitive to?
• Supply to anterior abdominal wall?
• Supply to diaphragmatic peritoneum?
• Supply to parietal peritoneum in pelvis?
• Sensitive to pain, temperature, touch & pressure (well-
localised pain)
• Peritoneum lining the anterior abdominal wall supplied by:
- T7 to T12 & L1
• Diaphragmatic peritoneum is supplied by:
- phrenic nerves C3, 4, 5 (referred pain to the shoulder tip)
• Pelvis parietal peritoenum supplied by:
- Obturator nerve L2, 3, 4
Describe the nerve supply to visceral peritoneum:
• Sensitive to?
• Supplied by?
• Brain?
• The visceral peritoneum is sensitive only to stretch & tearing without being sensitive to
touch, pressure or temperature (diffuse & poorly localised pain)
- Supplied by autonomic afferent nerves that supply the viscera or are traveling in the mesenteries
- The brain cannot localise visceral pain & this is often referred to a dermatome (e.g. appendix pain refers to the T10 dermatome)
What are the sites of referred pain of gallbladder?
- Upper right abdomen
- Right shoulder tip
- May radiate to the epigastrium, or around the lower ribs, or directly through to the back
When is bilaminar disc formed? What are the layers called?
• Conceptus ~ 12 days post fertilisation implanted in uterine mucosa
• Forming bilaminar disc:
1. Hypoblast
2. Epiblast
When does the bilmainar disc become trilaminar? What are the 3 layers called?
• Bilaminar disc becomes trilaminar (gastrulation) in the early stages of development (only 2 weeks post conception) • The 3 layers formed in week 3 are: 1. Ectoderm 2. Endoderm 3. Mesoderm
What structures are derived from the ectoderm (epiblast)?
- Neural tube
* Body wall
What structures are derived from mesoderm?
- Cardiovascular system
- Musculoskeletal system
- Body cavities (coeloms)
What structures are derived from endoderm?
- Gastrointestinal tract
- Respiratory tract
- Reproductive tract
What happens in day 17 of GI development?
- Notochord burrows from primitive node, between ectoderm & endoderm
- Undergoes a series of developmental changes
- Becomes a plate that induces the overlying ectoderm to become the neural plate
What happens in day 18 (end of week 3) of GI development?
Cephalic-caudal and lateral folding of t§rilaminar disc
What happens in cephalic-caudal and lateral folding of the trilaminar disc?
- Starts at end of week 3 (18 days)
- Head and tail folds meet at 2 lateral folds at umbilicus
- Creates:
- Endodermal tube of pharynx and intestinal tract
- Stomach and intestinal tract
- Glands associated with the gastrointestinal tract
What are the stages of embryonic folding in gut tube formation?
Cephalic-caudal folding in 3 stages to follow gut tube creation:
- Endoderm - “pinched-off” to form gut tube, communicates with yolk sac
- Mesoderm moves to what will become the posterior abdominal wall
Lateral folds close body wall and enclose intra-embryonic coelom (peritoneal cavity)
What does the amnion cover?
Connecting stalk/ vitelli-intestinal duct/ umbilical cord
Where abouts is the complete body wall free in amniotic cavity?
Above and below umbilicus
What is exomphalos?
- Failure of intestine to return to abdomen
* Lies within peritoneum and amnion in umbilical cord
What is gastroschisis?
- Failure of abdominal wall
* Contents not covered by peritoneum or amnion
The stomach and proximal part of the duodenum have a ventral mesentery, (ends 1/2 way along duodenum) which becomes ___?
- Lesser omentum
- Falciform ligament
=> Have free edges (as mesentery ends 1/2 way along duodenum)
