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Peritoneum & Peritoneal Cavity
Abdomen, Pelvis & Perineum Unit
Lecture 4
‫ حيدر جليل األعسم‬.‫د‬
Peritoneum
It is a thin serous membrane that lines walls of abdominal and pelvic
cavities (parietal peritoneum) & covers viscera (visceral peritoneum).
Peritoneal cavity is a potential space between parietal and visceral
layers. In males, this is a closed cavity, but in females, there is a
communication with the exterior through
the uterine tubes, uterus, and vagina.
Peritoneum secretes a small amount of
serous fluid (peritoneal fluid), which
lubricates surfaces of peritoneum and
allows free movement between viscera.
Extraperitoneal tissue is a layer of
connective tissue between fascial
lining of abdominal and pelvic walls
and parietal peritoneum; near
the kidneys this tissue contains a large
amount of fat, which supports the kidneys.
Embryology of peritoneal cavity
Embryonic Primordial abdominal cavity is
lined with mesoderm (parietal peritoneum).
The lumen of peritoneal sac is the peritoneal
cavity. As the organs develop, they
invaginate (protrude) into peritoneal sac,
acquiring a peritoneal covering, visceral
peritoneum. Some organs such as kidney,
pancreas and ascending and descending
colons protrude only partially into peritoneal
cavity (Retroperitoneal). Other viscera, such
as stomach, jejunum, ileum and spleen,
protrude completely into peritoneal sac and
are almost completely invested by visceral
peritoneum (Intraperitoneal). These viscera
are connected to abdominal wall by a
mesentery (two layers of peritoneum with a
thin layer of loose connective tissue
between them).
Folds of the peritoneum
They are folds of peritoneum that develops
from the original embryonic ventral and dorsal
mesentery of the abdomen and connect the
abdominal organs to each other or to abdominal
walls. Some of these folds (peritoneal ligaments,
omenta or mesenteries) permit blood, lymph
vessels, and nerves to reach the viscera.
Peritoneal Ligaments: two-layered folds of
peritoneum that connect solid viscera to
abdominal walls. Liver is connected to
diaphragm by falciform ligament, coronary
ligament, and right & left triangular ligaments.
Omenta: (omentum=single)
They are two-layered folds of peritoneum that
connect stomach to another viscus.
Mesenteries: are two-layered folds of
peritoneum connecting parts of the intestines
to posterior abdominal wall:
Omentum
two-layered folds of peritoneum connecting stomach to another viscus.
Lesser omentum extends from lesser curvature of stomach and first part
of duodenum to fissure of ligamentum
venosum and porta hepatis on undersurface
of liver. It is divided into two parts:
Medial hepatogastric ligament
Lateral hepatoduodenal ligament
Greater omentum connects greater
curvature of stomach and first part of
duodenum to transverse colon. It hangs
down like an apron in front of coils of
small intestine and is folded back on
itself to be attached to transverse colon.
Gastrosplenic omentum (ligament) connects stomach to the hilum of
spleen.
Mesenteries
Mesentery of small intestine: is a large, fan-shaped,
double-layered fold of peritoneum that connects
jejunum and ileum to posterior abdominal wall. Its
superior attachment is at duodenojejunal junction (to
the left of upper lumbar part of vertebral column). It
passes obliquely downward and to the right, ending at
ileocecal junction near upper border of right sacroiliac
joint. It contain aa, vv, nn & lymp.vv.
Transverse mesocolon: is a fold of peritoneum that
connects transverse colon to posterior abdominal wall.
It is originated from posterior abdominal wall across
anterior surface of head and body of pancreas and pass
outward to surround transverse colon.
Sigmoid mesocolon: is an inverted, V-shaped
peritoneal fold that attaches sigmoid colon to
abdominal wall. Apex of the 'V' is near the division of
left common iliac artery into its internal & external
branches. Sigmoid and superior rectal vessels, along
with the nerves and lymphatics associated with the
sigmoid colon, pass through this peritoneal fold.
Subdivisions of Peritoneal Cavity
The peritoneal cavity is the largest cavity in the body. It is divided into
two parts: Greater sac & Lesser sac (omental bursa). The greater and
lesser sacs are in free communication with one another through an oval
opening of lesser sac, or epiploic foramen.
Lesser Sac: lies behind stomach &
lesser omentum. The Boundaries are:
• Superiorly: diaphragm
• Inferiorly: extend till layers of
greater omentum fuse together.
• Left margin of the sac is formed by
spleen and gastrosplenic omentum &
splenicorenal ligament.
• Right margin opens into the greater sac
through opening of lesser sac (epiploic foramen)
Subdivisions of Peritoneal Cavity
Greater Sac: is the main and larger part of peritoneal cavity and extends
from diaphragm down into pelvis. Transverse mesocolon (mesentery of
transverse colon) divides abdominal cavity into:
A. Supracolic compartment, containing stomach, liver, and spleen,
B. Infracolic compartment, containing
small intestine and ascending and
descending colon. The infracolic
compartment lies posterior to the
greater omentum and is divided
into right & left infracolic spaces
by mesentery of the small intestine.
Free communication occurs between
supracolic and infracolic compartments
through paracolic gutters, grooves between
lateral aspect of ascending or descending
colon and posterolateral abdominal wall.
Epiploic foramen:
Boundaries:
• Anteriorly: Free border of
lesser omentum which
contain hepatic triad (bile
duct & hepatic artery
anteriorly, and portal vein
posteriorly)
• Posteriorly: Inferior vena
cava
• Superiorly: Caudate
process of the caudate
lobe of the liver
• Inferiorly: First part of the
duodenum
Subdivisions of Peritoneal Cavity
Duodenal Recesses: (Superior duodenal, Inferior duodenal, Paraduodenal &
Retroduodenal recesses). They are four small pocket-like pouches of
peritoneum close to duodenojejunal junction:
Cecal Recesses: (superior ileocecal, inferior ileocecal, and retrocecal
recesses). They are folds of peritoneum close to cecum and produce
three peritoneal recesses.
Intersigmoid Recess: is situated at apex
of inverted, V-shaped root of sigmoid
mesocolon; its mouth opens downward.
Subphrenic Spaces:
Right & left anterior subphrenic spaces
lie between diaphragm and liver, on each
side of falciform ligament.
Right posterior subphrenic space lies
between right lobe of liver, right kidney,
and right colic flexure.
Right extraperitoneal space lies between
the layers of the coronary ligament and
is therefore situated between the liver
and the diaphragm.
Subdivisions of Peritoneal Cavity
Paracolic Gutters:
Paracolic gutters lie on the lateral
and medial sides of the ascending
and descending colons,
respectively. The subphrenic
spaces and the paracolic gutters
are clinically important because
they may be sites for the
collection and movement of
infected peritoneal fluid.
Nerve Supply of the Peritoneum
A: Parietal peritoneum: is sensitive to pain, temperature, touch, and
pressure.
• Parietal peritoneum lining anterior abdominal wall is supplied by
lower 6 thoracic & first lumbar nerves.
• Central part of diaphragmatic peritoneum is supplied by Phrenic
nerves;
• Peripheral part of diaphragmatic peritoneum is supplied by lower 6
thoracic nerves.
• Parietal peritoneum in the pelvis is mainly supplied by Obturator
nerve, a branch of the lumbar plexus.
B: Visceral peritoneum is sensitive only to stretch and tearing, but not
sensitive to touch, pressure or temperature. It is supplied by autonomic
afferent nerves that supply the viscera or are traveling in the
mesenteries. Over-distention of a viscus leads to the sensation of pain.
Functions of the Peritoneum
1- Secretion of peritoneal fluid to lubricate and glide mobile viscera
easily on one another.
2- Peritoneal coverings of intestine tend to stick together in the presence
of infection. Greater omentum, which is kept constantly on the move by
peristalsis of neighboring intestinal tract, may adhere to other peritoneal
surfaces around a focus of infection. therefore, many of intraperitoneal
infections are sealed off and remain localized by greater omentum which
is called Watch dog or policeman of the abdomen.
3- Peritoneal folds (mesenteries) play an important part in suspending
various organs within peritoneal cavity and serve as a means of
conveying blood vessels, lymphatics, and nerves to these organs.
4- Large amounts of fat are stored in the peritoneal ligaments and
mesenteries, and especially large amounts can be found in the greater
omentum.
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