8 Peritoneal and GI development 1 Flashcards

1
Q

What is the peritoneum?

A

Thin serous membrane that lines the walls of the abdominal & pelvic cavities & “clothes” the viscera (organs)

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2
Q

What is the parietal peritoneum?

A

Lines the walls of the abdominal and pelvic cavities

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3
Q

What is the visceral peritoneum?

A

Covers the viscera (organs)

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4
Q

What is the peritoneal cavity? What is it divided into?

A
  • Potential space between the parietal and visceral peritoneum
  • Divided into greater and lesser sacs
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5
Q

What is peritoneal fluid?

A
  • 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)

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6
Q

What structures do the peritoneum form?

A
  • Omenta (greater and lesser)
  • Mesenteries
  • Ligaments
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7
Q

What is the difference in the peritoneal cavities of males and females?
Clinical risk?

A
  • 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

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8
Q

Where is the extraperitoneal tissue (connective tissue) found?

A

Between the parietal peritoneum and the fascial lining of the abdomen and pelvic walls (transversalis fascia)

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9
Q

What does retroperitoneal mean?

A

Any structure outside the peritoneal cavity

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10
Q

How is the peritoneal cavity divided?

A
  1. Greater sac:
    • Main compartment
    • Extends from the diaphragm down into the pelvis
  2. Lesser sac (omental bursa):
    • Smaller and lies behind the stomach and lesser omentum
    • Extends slightly into the greater omentum
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11
Q

What structures allows free communications between the greater and less omentum?

A

Epiploic foramen of Winslow

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12
Q

What is the function of the epiploic foramen (omental foreamen/ foramen of Winslow)?

A

The greater and lesser sacs are in free communication via epiploic foramen

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13
Q

What are the triad of vessels in the free border of the lesser omentum?

A
  1. Portal vein - posteriorly
  2. Hepatic artery proper - anteriorly to the left
  3. Common bile duct - anteriorly to the right
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14
Q

What is the greater omentum?

A
  • 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
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15
Q

What structure is the “Policeman of the abdomen”? Function?

A
  • Greater omentum

* Drawn to diseased or perforated structures to seal them off

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16
Q

What is the lesser omentum?

A

• 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

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17
Q

What is the hepatoduodenal ligament?

A

The free edge of the lesser omentum containing the portal vein, hepatic artery proper & common bile duct

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18
Q

What are mesenteries?

A
  • 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
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19
Q

Name the mesenteries in the abdomen

A
  1. Small intestine:
    • The mesentery
2. Colon: 
• Ascending
• Transverse
• Descending 
• Sigmoid mesocolons
  1. Vermiform appendix:
    • Mesoappendix
  2. Rectum:
    • Mesorectum
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20
Q
What is the The Mesentery?
Where does base start?
Which structures does it cross?
How long?
Contains branches of which structures?
A
  • 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
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21
Q

What are the anastomotic arcade differences between the jejunum and ileum?

A

• The SMA branches are a series of anastomotic arcades within The mesentery

  1. Jejunum:
    • Has few arcades
    • Long vasa recta
  2. Ileum:
    • Has many arcades
    • Short vasa recta
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22
Q

Sigmoid mesocolon:
What is it?
Root?
Transmits which vessels?

A
  1. Double-layered fold of peritoneum that connects the sigmoid colon to the posterior abdominal wall.
  2. Root:
    • In the left iliac fossa, crossing the bifurcation of the left common iliac vessels and the left ureter
  3. Transmits:
    • The sigmoid branches of the inferior mesenteric vessels plus nerves and lymphatics
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23
Q

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

A

Paraduodenal recesses

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24
Q

Transverse mesocolon:
Function?
Root?
Carries branches?

A
  1. Suspends the transverse colon from the posterior abdominal wall
  2. Root:
    • Just inferior to the pancreas
  3. Carries branches of the middle colic vessels
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25
Q

Transverse mesocolon divides the peritoneal cavity (greater sac) into which compartments?

A
  1. Supracolic

2. Infracolic

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26
Q

Which organs are contained in the supracolic compartments?

A
  • Liver
  • Gallbladder
  • Stomach
  • Spleen
27
Q

Which organs are contained in the infracolic compartments?

A
  • Jejunum
  • Ileum
  • Ascending and descending colon
28
Q

How is the infra colic compartment divided into right and left halves?

A

By The mesentery with each half having a parabolic gutter

29
Q

Name the peritoneal pouches, recesses, spaces and gutters present within the peritoneum?

A
  1. Hepatorenal recess (Morison’s pouch)

Pelvic peritoneal pouches:

  1. Rectovesical pouch
  2. Rectouterine pouch (of Douglas)
  3. Vesicouterine pouch
30
Q

What is the hepatorenal recess (Morison’s pouch)? What may collect there?

A
  • Rights posterior sub hepatic space

* Blood/ pus may collect here with the latter forming abscesses particularly if lying recumbent

31
Q

What is the rectovesical pouch?

A
  • In males

* Separates rectum from urinary bladder

32
Q

What is the rectouterine pouch (of Douglas)?

A
  • In females

* Separates the rectum from uterus

33
Q

What is the vesicouterine pouch?

A
  • In females

* Separates the urinary bladder from uterus

34
Q

What is a peritoneal fold?

A

Reflection of peritoneum with more or less sharp borders

35
Q

How are peritoneal folds formed?

A

Formed by peritoneum that covers blood vessels, duct and obliterated foetal vessels

36
Q

Name the peritoneal folds visible on the parietal peritoneum on the interior of the anterior abdominal wall

A
  • Median umbilical fold
  • 2 medial umbilical folds
  • 2 lateral umbilical folds
37
Q

What is the median umbilical fold?

A

Embryological remnant of the urachus that extends from the urinary bladder to the umbilicus

38
Q

What are the 2 medial umbilical folds?

A

Embryological remnant of the umbilical arteries extending from the internal iliac arteries to the umbilicus

39
Q

What are the 2 lateral umbilical folds?

A

Raised by the inferior epigastric arteries extending from the deep inguinal rings on each side to the arcuate lines

40
Q

What are the peritoneal ligaments?

A

2 layered folds of peritoneum that connect 2 organs together

41
Q

Peritoneal ligaments in the liver?

A

Liver is connected to diaphragm by:
• falciform ligament
• coronary ligaments
• triangular ligaments (right and left)

42
Q

What is an intraperitoneal organ?

A

When organ is almost totally covered with visceral peritoneum & is suspended within the peritoneal cavity by a mesentery

43
Q

What is a retroperitoneal organ? And the types?

A

• Lie behind or outside the peritoneum are only partially covered with visceral peritoneum

  1. Primary - always retroperitoneal
  2. Secondary - initially intraperitoneal but migrate retroperitoneally during embryogenesis and lose their mesentery
44
Q

What organ has absorbed its peritoneal covering and is truly intraperitoneal?

A

Ovary

45
Q

Which organs are primary retroperitoneal?

A
1. Urinary:
• Suprarenal/ adrenal glands
• Kidneys
• Ureters
• Bladder
  1. Circulatory:
    • Abdominal aorta
    • Inferior vena cava
  2. Digestive:
    • Oesophagus (final part)
    • Rectum (middle 1/3 with lower 1/3 totally extraperitoneal)
46
Q

Which organs are secondary retroperitoneal?

A
  • 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)
47
Q

Describe the nerve supply to parietal peritoneum:
• Sensitive to?
• Supply to anterior abdominal wall?
• Supply to diaphragmatic peritoneum?
• Supply to parietal peritoneum in pelvis?

A

• 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

48
Q

Describe the nerve supply to visceral peritoneum:
• Sensitive to?
• Supplied by?
• Brain?

A

• 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)
49
Q

What are the sites of referred pain of gallbladder?

A
  • Upper right abdomen
  • Right shoulder tip
  • May radiate to the epigastrium, or around the lower ribs, or directly through to the back
50
Q

When is bilaminar disc formed? What are the layers called?

A

• Conceptus ~ 12 days post fertilisation implanted in uterine mucosa
• Forming bilaminar disc:
1. Hypoblast
2. Epiblast

51
Q

When does the bilmainar disc become trilaminar? What are the 3 layers called?

A
• 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
52
Q

What structures are derived from the ectoderm (epiblast)?

A
  • Neural tube

* Body wall

53
Q

What structures are derived from mesoderm?

A
  • Cardiovascular system
  • Musculoskeletal system
  • Body cavities (coeloms)
54
Q

What structures are derived from endoderm?

A
  • Gastrointestinal tract
  • Respiratory tract
  • Reproductive tract
55
Q

What happens in day 17 of GI development?

A
  • 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
56
Q

What happens in day 18 (end of week 3) of GI development?

A

Cephalic-caudal and lateral folding of t§rilaminar disc

57
Q

What happens in cephalic-caudal and lateral folding of the trilaminar disc?

A
  • Starts at end of week 3 (18 days)
  • Head and tail folds meet at 2 lateral folds at umbilicus
  • Creates:
  1. Endodermal tube of pharynx and intestinal tract
  2. Stomach and intestinal tract
  3. Glands associated with the gastrointestinal tract
58
Q

What are the stages of embryonic folding in gut tube formation?

A

Cephalic-caudal folding in 3 stages to follow gut tube creation:

  1. Endoderm - “pinched-off” to form gut tube, communicates with yolk sac
  2. Mesoderm moves to what will become the posterior abdominal wall

Lateral folds close body wall and enclose intra-embryonic coelom (peritoneal cavity)

59
Q

What does the amnion cover?

A

Connecting stalk/ vitelli-intestinal duct/ umbilical cord

60
Q

Where abouts is the complete body wall free in amniotic cavity?

A

Above and below umbilicus

61
Q

What is exomphalos?

A
  • Failure of intestine to return to abdomen

* Lies within peritoneum and amnion in umbilical cord

62
Q

What is gastroschisis?

A
  • Failure of abdominal wall

* Contents not covered by peritoneum or amnion

63
Q

The stomach and proximal part of the duodenum have a ventral mesentery, (ends 1/2 way along duodenum) which becomes ___?

A
  • Lesser omentum
  • Falciform ligament

=> Have free edges (as mesentery ends 1/2 way along duodenum)