Abdominal Wall Layers and Peritoneum

Question 1

What is the rectus sheath?

Answer 1

The central abdominal aponeurosis, formed by the interwoven aponeurotic fibres of the external oblique, internal oblique and transverse abdominus muscles

The rectus sheath encloses the rectus abdominus, pyramidalis if present, superior and inferior epigastric vessels, and the termination of the lower 5 intercostal nerves and T12 spinal nerve

Question 2

What is the arcuate line?

Answer 2

A horizontal line approximately halfway between the umbilicus and the pubic symphysis. This demarcates the point where the posterior wall of the rectus sheath ends, and the aponeurosis of the EO, IO and TA combine to form an anterior wall only.

Question 3

What are the layers of the anterior and posterior walls of the rectus sheath?

Answer 3

Above the arcuate line:
Anterior wall - EO and half of IO
Posterior wall: half of IO and TA

Below the arcuate line:
Anterior wall only: EO, IO, TA

Question 4

What is the linea alba?

Answer 4

A touch tendinous midline structure running vertically along the middle of the rectus sheath (formed by the interwoven fibres of the aponeuroses of EO, IO and TA)

Attachments:
xiphoid process and pubic symphysis

Question 5

What are the layers of the abdominal wall?

Answer 5

Superficial to deep:

Skin
Subcutaneous tissue

Campers fascia - fatty superficial fascial layer
Scarpa’s fascia - deep fibrous fascial layer

External oblique
Internal oblique
Rectus abdominus
Transverse abdominus
Pyramidalis

Transversalis fascia
Extraperitoneal fat
Peritoneum

Question 6

What is the peritoneum?

Answer 6

A continuous membrane (made of simple squamous epithelial cells) lining the abdominal cavity and covering the abdominal organs.

Made of two layers (parietal and visceral) that are continuous with each other.

Supports viscera and provides pathways for neurovascular and lymph vessels to travel to and from viscera.

Question 7

What are the layers of the peritoneum?

Answer 7

Outer: parietal peritoneum
- lines internal surface of abdominopelvic wall

Intermediate: peritoneal cavity

• thin space between parietal and visceral peritoneal layers
• contains a small amount of lubricating fluid
• fluid allows viscera to move without friction, and contains immune cells to resist infection

Internal: visceral peritonem
- covers the majority of abdominal viscera

Question 8

What is the innervation of the different parietal layers?

Answer 8

Peritoneal:

• innervated by the same cutaneous nerves as the region of the abdominal wall it lies within
• sensitive to pain, temperature, pressure and touch

Visceral:

• innervated by the organs it covers
• sensitive only to stretch and tearing (poorly localized pain)

Question 9

Which layer of peritoneum is more sensitive to nociception and other sensory input?

Answer 9

Parietal - innervated by the same cutaneous nerves that innervate the region of the abdominal wall they lie within. Sensitive to pain, touch, pressure, and temperature.

Visceral is innervated by the same nerves that innervate the organ and has only poorly localized pain sensation from stretch and tearing.

Question 10

What is the difference between intraperitoneal and extraperitoneal organs?

Answer 10

Intraperitoneal - completely contained within peritoneal membrane, lined with visceral peritoneum on all surfaces.
- most are attached to posterior abdominal wall by mesenteries

Extraperitoneal / retroperitoneal organs:

• only anterior wall is covered by visceral peritoneum
• posterior wall is covered by adventitia and lies behind the peritoneal membrane

Question 11

What are the 3 intraperitoneal and 9 extraperitoneal organs?

Answer 11

Intraperitoneal:

• stomach
• liver
• spleen

Extraperitoneal:
Suprarenal / adrenal glands
Aorta / IVC
Duodenum (except cap)
Pancreas (except tail)
Ureters
Colon (except transverse)
Kidneys
Osophagus
Rectum

Question 12

What are the peritoneal ligaments?

Answer 12

Double layered folds of peritoneum that connect abdominal viscera to other organs or to the abdominal wall

Liver (5)

• coronary
• falciform
• round ligament
• hepatogastric
• hepatoduodenal

Stomach (4)

• hepatogastric
• gastrophrenic
• gastrosplenic
• gastrocolic

Spleen (2)

• gastrosplenic
• splenorenal

Question 13

What are the 5 peritoneal ligaments of the liver?

Answer 13

coronary
falciform
round
hepatogastric (part of lesser omenta)
hepatoduodenal (part of lesser omenta)

Question 14

What are the 4 peritoneal ligaments of the stomach?

Answer 14

hepatogsatric (part of lesser omenta)
gastrophrenic
gastrosplenic
gastrocolic

Question 15

What are the 2 peritoneal ligaments of the spleen?

Answer 15

gastrosplenic

splenorenal

Question 16

What are mesenteries?

Answer 16

• double layer of peritoneum caused by invagination of peritoneum by an organ
• connects organ to posterior abdominal wall

Question 17

what are the omenta?

Answer 17

Greater omenta:

• 4 layered fold of peritoneum hanging down like an apron
• from greater curvature of stomach and proximal duodenum to anterior surface of transverse colon and mesentery
• acts as abdominal policeman
• named for organ it connects to (mesogastrium, mesoappendix, mesocolon etc)

Lesser omenta:

• from lesser curvature of stomach and proximal duodenum to liver
• 2 layered fold of peritoneum
• 2 components: hepatogastric ligament (flat sheet) and hepatoduodenal ligament (free edge containing portal triad)