Peritoneum
Bursae of peritoneal cavity
The PERITONEUM is serous membrane
that covers the walls of abdominal cavity and viscera in abdomen and pelvis. It
may be subdivided into parietal peritoneum and visceral
peritoneum. Transition of parietal peritoneum into visceral peritoneum realizes
by derivatives: ligament, mesentery and omentum.
If organ covered by peritoneum from all sides, such position is called intraperitoneal; if from three sides - mesoperitoneal
position; if only one side
- extraperitoneal or retroperitoneal.
Abdominal cavity
is limited:
·
above - by diaphragm
·
anteriorly and laterally - by muscles, fasciae, skin
·
behind - by lumbar and sacral portions of backbone and
lumbar muscles
·
from below – by bones,
ligaments and muscles of pelvis.
Abdominal cavity contains the organs of digestive and
urogenital systems and spleen.
Peritoneal cavity is complex of fissure between abdominal organs and walls
lined by parietal and visceral sheets that contain serous liquid. It can be
subdivided into superior storey and inferior storey, also cavity of lesser
pelvis.
Superior storey of peritoneal
cavity positioned between diaphragm and level of mesocolon
of transverse colon. It contains:
• hepatic bursa
surrounds right hepatic lobe and gallbladder;
• pregastric
bursa accommodates left hepatic lobe and anterior wall of stomach;
• omental
bursa is situated behind lesser omentum and it is
in touch with posterior stomach surface.
Lesser omentum
is formed by double peritoneal sheet that forms of hepatogastric
ligament and hepatoduodenal ligament.
Lesser omentum carries common bile duct,
portal vein and proper hepatic artery (DVA).
The lesser omentum (small omentum;
gastrohepatic omentum; Latin: omentum minus) is the double layer of peritoneum that extends from the liver to the lesser
curvature of the stomach and the start of the duodenum.
The primitive mesentery of a six weeks’
human embryo, half schematic. (Lesser omentum labeled at left.)
Schematic and enlarged cross-section through the body of a human embryo
in the region of the mesogastrium, at end of third
month
The lesser omentum is extremely thin, and is
continuous with the two layers ofperitoneum
which cover respectively the antero-superior
and postero-inferior surfaces of the stomach and
first part of the duodenum.
When these two
layers reach the lesser curvature of the stomach and the upper border of the duodenum, they join
together and ascend as a double fold to the porta hepatis.
To the left of the porta, the fold is attached
to the bottom of the fossa for the ductus venosus, along which it
is carried to the diaphragm, where the two layers separate to embrace the end
of the esophagus.
At the right border of the lesser omentum,
the two layers are continuous, and form a free margin which constitutes the
anterior boundary of the epiploic foramen.
Anatomically, the lesser omentum is
divided into ligaments, each starting with the prefix "hepato"
to indicate that it connects to the liver at one end.
Most sources divide it into two parts:[1]
·
hepatogastric ligament: the portion connecting to the lesser curvature of the
stomach
·
hepatoduodenal ligament: the portion connecting to the duodenum
In some cases, the following ligaments are considered part
of the lesser omentum:
·
hepatophrenic ligament: the portion connecting to the thoracic diaphragm[2]
·
hepatoesophageal ligament: the portion connecting to the esophagus[3]
·
hepatocolic ligament: the portion connecting to the colon
Between
the two layers of the lesser omentum, close to the
right free margin, are thehepatic artery, the common bile duct, the portal vein, lymphatics, and the hepatic plexus of nerves—all these structures being enclosed in a
fibrous capsule (Glisson's capsule).
Between the layers of the lesser omentum,
where they are attached to the stomach, run the right and left gastric arteries, as well as the gastric veins.
Hepatic
bursa communicates with omental bursa by the medium
of epiploic foramen (of Winslow). Last limited from above by caudate lobe of the liver, from below -
by superior part of duodenum, anteriorly - hepatoduodenal ligament, behind - by parietal sheet of
peritoneum.
Greater
omentum develops from 4 peritoneal sheets, which continue from gastrocolic ligament and, freely hanging down, covers the abdominal organs in
front. The gastrocolic ligament connects the transverse colon with the greater curvature of
the stomach.
The greater
omentum (also
the great omentum, omentum
majus, gastrocolic omentum, epiploon,
or, especially in animals, caul) is a large fold of visceralperitoneum
that hangs down from
the stomach. It extends from the greater curvature of the stomach, passing in front
of the small intestines and reflects on itself to ascend to the transverse
colon before reaching to the posterior abdominal
wall. The common anatomical term "epiploic"
derives from "epiploon" from the Greek
"epipleein" meaning to float or sail on,
since the greater omentum appears to float on the
surface of the intestines.
The functions of
the greater omentum are:
·
Fat deposition, having varying amounts of adipose
tissue[1]
·
Immune contribution, having milky
spots of macrophage collections[1]
·
Infection and wound isolation;
It may also physically limit the spread of intraperitoneal
infections.[1] The greater omentum
can often be found wrapped around areas of infection and trauma.
The greater omentum is the largest
peritoneal fold. It consists of a double sheet ofperitoneum
, folded on itself so that it is made up of four layers.
The
two layers which descend from the greater curvature of the stomach and
commencement of the duodenum pass in front of thesmall
intestines, sometimes as low down as the pelvis;
they then turn upon themselves, and ascend again as far as the transverse
colon, where they separate and enclose that part of the intestine.
These
individual layers may be easily demonstrated in the young subject, but in the
adult they are more or less inseparably blended.
The
left border of the greater omentum is continuous with
the gastrolienal
ligament; its right border extends as far as the commencement of the duodenum.
The
greater omentum is usually thin, presents a cribriform appearance, and always contains some adipose
tissue, which in obese people accumulates in considerable quantity.
The greater omentum is often defined
to encompass a variety of structures. Most sources include the following two:[2][3]
·
Gastrocolic
ligament - to transverse
colon (occasionally on its
own considered synonymous with "greater omentum"[2])
·
Gastrosplenic
ligament - to spleen
The splenorenal
ligament (from the left kidney to the spleen)
is occasionally considered part of the greater omentum.[
The right and left gastroepiploic
vessels provide the sole
blood supply to the greater omentum. Both are
branches of the celiac
trunk. The right gastroepiploic is a branch of
the gastroduodenal
artery, which is a branch of the common
hepatic artery, which is a branch of the celiac trunk. The left gastroepiploic artery is the largest branch of the splenic
artery, which is a branch of the celiac trunk. The right and left gastroepiploic
vessels anastomose within the two layers of the anterior greater omentum along the greater curvature of the stomach.
The
greater omentum develops from the dorsal
mesentery that
connects the stomach to the posterior abdominal wall.
During stomach development, the stomach undergoes its first 90° rotation along
the axis of the embryo, so that posterior structures are moved to the left and
structures anterior to the stomach are shifted to the right. As a result, the
dorsal mesentery folds over on itself, forming a pouch with its blind end on
the left side of the embryo. A second approximately 90° rotation of the
stomach, this time in the frontal
plane, moves structures inferior if they were originally to the left of
the stomach, and superior if they were originally to the stomach's right.
Consequently, the blind-ended sac (also called the lesser
sac) formed by the dorsal mesentery is brought inferiorly, where it
assumes its final position as the greater omentum. It
grows to the point that it covers the majority of the small and large
intestine.
Omentectomy refers to the surgical
removal of the omentum, a relatively simple procedure
with no major side effects, that is performed in cases where there may be
spread of cancerous tissue into the omentum. Examples
for this conditions are ovarian
cancer and advanced or
aggressive endometrial
cancer as well as
intestinal cancer. The procedure is generally done as an add-on when the
primary lesion is removed.
Inferior
floor of peritoneal
cavity extends from mesocolon of transverse colon to entrance into lesser pelvis.
Root
of small intestine mesentery divides the inferior storey into right and
left mesenteric sinuses. They
accommodate the loops of small intestine. Right mesenteric sinus is bordered by
mesenteric root and ascending colon. In place, where ileum
continues into cecum superior and inferior ileocecal
recesses are situated. One can see retrocecal
recess behind cecum. Right paracolic sulcus runs between ascending colon and parietal
peritoneum of lateral abdominal wall. Mesenteric root, descending colon and
sigmoid colon border left mesenteric sinus. Superior and
inferior duodenal recesses are positioned in area of duodenojejunal
junction. Mesocolon of sigmoid forms intersigmoidal
recess. Left paracolic sulcus runs between descending colon and parietal
peritoneum of left abdominal wall.
Parietal sheet of peritoneum covering back surface of anterior
abdominal form plicae (folds) and fossae. The median
umbilical fold contains the remnant of the embryonic urachus;
the medial umbilical folds carry obliterated umbililal
arteries; lateral umbilical folds contain inferior epigastric
arteries. Supravesical fossae
positioned between median and medial umbilical folds. Medial umbilical
fossae located between medial and lateral umbilical folds. Lateral
umbilical fossae located laterally from lateral umbilical folds. Medial
and lateral umbilical fossae can be projected into superficial inguinal ring
and deep inguinal ring.
Cavity
of lesser pelvis
Peritoneal
cavity in the male pelvis contains rectovesical excavation
(pouch). Peritoneum in the female between uterus and urinary bladder form vesicouterinae excavation. Behind the uterus
peritoneum descends into the rectouterine
pouch (pouch of Douglas), which is the lowest point of the peritoneal
cavity. That is why some liquid from all peritoneal cavity
can collect here during some pathology. The entrance into the rectouterine pouch is narrowed by the rectouterine
folds, in which the rectouterine muscles run.
The
glistening appearance of the deep surface of the abdominal wall and of the
surfaces of the exposed viscera is due to the fact that the former is lined,
and the latter are more or less completely covered, by a serous membrane, the
peritoneum.
The
Peritoneum (Tunica Serosa)—The peritoneum is the
largest serous membrane in the body, and consists, in the male, of a closed
sac, a part of which is applied against the abdominal parietes,
while the remainder is reflected over the contained viscera. In the female the
peritoneum is not a closed sac, since the free ends of the uterine tubes open
directly into the peritoneal cavity. The part which lines the parietes is named the parietal portion of the peritoneum;
that which is reflected over the contained viscera constitutes the visceral
portion of the peritoneum. The free surface of the membrane is smooth, covered
by a layer of flattened mesothelium, and lubricated by a small quantity of
serous fluid. Hence the viscera can glide freely against the wall of the cavity
or upon one another with the least possible amount of friction. The attached
surface is rough, being connected to the viscera and inner surface of the parietes by means of areolar tissue, termed the subserous areolar tissue. The
parietal portion is loosely connected with the fascial
lining of the abdomen and pelvis, but is more closely adherent to the under
surface of the diaphragm, and also in the middle line of the abdomen.
The
space between the parietal and visceral layers of the peritoneum is named the
peritoneal cavity; but under normal conditions this cavity is merely a
potential one, since the parietal and visceral layers are in contact. The
peritoneal cavity gives off a large diverticulum, the omental
bursa, which is situated behind the stomach and adjoining structures; the neck
of communication between the cavity and the bursa is termed the epiploic foramen (foramen of Winslow). Formerly the main
portion of the cavity was described as the greater, and the omental
bursa as the lesser sac.
The
peritoneum differs from the other serous membranes of the body in presenting a
much more complex arrangement, and one that can be clearly understood only by
following the changes which take place in the digestive tube during its
development.
The
abdominal cavity (the space bounded by the vertebrae, abdominal
muscles,diaphragm and pelvic
floor) should not be confused with the intraperitoneal space(located within the
abdominal cavity, but wrapped in peritoneum). The structures within the intraperitoneal space are called "intraperitoneal"
(e.g. the stomach),
the structures in the abdominal cavity that are located behind the intraperitoneal space are called "retroperitoneal"
(e.g. the kidneys),
and those structures below the intraperitoneal space
are called "subperitoneal" or "infraperitoneal" (e.g. the bladder).
Although
they ultimately form one continuous sheet, two types or layers of peritoneum
and a potential space between them are referenced:
·
The
outer layer, called the parietal
peritoneum, is attached to the abdominal
wall and the pelvic
walls.[1]
·
The
inner layer, the visceral
peritoneum, is wrapped around the internal organs that are located inside
the intraperitoneal space. It is thinner than the
parietal peritoneum.
·
The
potential space between these two layers is the peritoneal
cavity; it is filled with a small amount (about 50 mL) of slipperyserous
fluid that allows the two
layers to slide freely over each other.
·
The
term mesentery is often used to refer to a double layer
of visceral peritoneum. There are often blood vessels, nerves, and other
structures between these layers. The space between these two layers is
technically outside of the peritoneal sac, and thus not in the peritoneal
cavity.
Peritoneal
folds are omenta, mesenteries and ligaments; they
connect organs to each other or to the abdominal wall.[2] There are two main regions of the
peritoneum, connected by the epiploic
foramen (also known as the omental
foramen or foramen of winslow):
·
The greater
sac (or general cavity of the abdomen),
represented in red in the diagrams above.
·
The lesser
sac (or omental
bursa), represented in blue. The lesser sac is divided into two "omenta":
·
The lesser
omentum (or gastrohepatic)
is attached to the lesser
curvature of the stomach and
the liver.
·
The greater
omentum (or gastrocolic)
hangs from the greater
curve of the stomach and
loops down in front of the intestinesbefore
curving back upwards to attach to the transverse colon.
In effect it is draped in front of the intestines like an apron and may serve
as an insulating or protective layer.
The mesentery is the part of the peritoneum
through which most abdominal organs are attached to the abdominal wall and
supplied withblood and lymph vessels and nerves.
In addition, in the pelvic
cavity there are several
structures that are usually named not for the peritoneum, but for the areas
defined by the peritoneal folds:
female
The
peritoneum develops ultimately from the mesoderm of the trilaminar
embryo. As the mesoderm differentiates, one region known as the lateral
plate mesoderm splits to
form two layers separated by an intraembryonic
coelom. These two layers develop later into the visceral and parietal
layers found in all serous
cavities, including the peritoneum.
As
an embryo develops, the various abdominal organs
grow into the abdominal cavity from structures in the abdominal wall. In this
process they become enveloped in a layer of peritoneum. The growing organs
"take their blood vessels with them" from the abdominal wall, and
these blood vessels become covered by peritoneum, forming a mesentery.[citation
needed]
Peritoneal
folds develop from the ventral and dorsal
mesentery of the embryo.[2]
In
one form of dialysis,
called peritoneal
dialysis, a glucose solution is sent through a tube into the
peritoneal cavity. The fluid is left there for a prescribed amount of time to
absorb waste products, and then removed through the tube. The reason for this
effect is the high number of arteries and veins in the peritoneal cavity.
Through the mechanism of diffusion,
waste products are removed from the blood.
Main
article: Primary
peritoneal carcinoma
Primary
peritoneal cancer is a cancer of the cells lining the peritoneum.
The
structures in the abdomen are classified as intraperitoneal, retroperitoneal or infraperitoneal
depending on whether they are covered with visceral peritoneum and whether they
are attached by mesenteries (mensentery, mesocolon).
Structures
that are intraperitoneal are generally mobile, while those that
are retroperitoneal are relatively fixed in their
location.
Some
structures, such as the kidneys, are "primarily retroperitoneal",
while others such as the majority of the duodenum, are
"secondarily retroperitoneal", meaning that structure developed intraperitoneally but lost its mesentery and thus became
retroperitoneal.
The
SPLEEN lies in epigastrium and belongs to secondary lymphatic organs and
is a big lymphatic node. Spleen is disposed in left hypochondriac region on the
level of 9 th -11th
ribs. Spleen has inferior margin and superior margin, anterior
extremity and posterior extremity. It has a diaphragmatic surface
(superior) and visceral surface (inferior). To the last adjoin stomach (facies gastrica), left kidney
with suprarenal gland (facies renalis),
left colic flexure (facies colica)
and tail of pancreas (facies pancreatica).
Place on visceral surface, where vessels and nerves enter and leave, is called
as splenic hilus.
Spleen is covered by peritoneum from all sides (lies intraperitoneally).
Spleen
is covered by fibrous capsule, from which numerous small fibrous bands, trabeculae are given off in all directions into
parenchyma, these uniting, and constitute the framework of the spleen. Parenchyma
consists of splenic pulp, which has a white pulp
and red pulp and its structure described in detail in histology course.
To trace the membrane from one viscus to another, and from the
viscera to the parietes, it is necessary to follow
its continuity in the vertical and horizontal directions, and it will be found
simpler to describe the main portion of the cavity and the omental
bursa separately.
Vertical
Disposition of the Main Peritoneal Cavity (greater sac)—It is convenient to
trace this from the back of the abdominal wall at the level of the umbilicus.
On following the peritoneum upward from this level it is seen to be reflected
around a fibrous cord, the ligamentum teres (obliterated umbilical vein), which reaches from the
umbilicus to the under surface of the liver. This reflection forms a somewhat
triangular fold, the falciform ligament of the liver,
attaching the upper and anterior surfaces of the liver to the diaphragm and
abdominal wall. With the exception of the line of attachment of this ligament
the peritoneum covers the whole of the under surface of the anterior part of the
diaphragm, and is continued from it on to the upper surface of the right lobe
of the liver as the superior layer of the coronary ligament, and on to the
upper surface of the left lobe as the superior layer of the left triangular
ligament of the liver. Covering the upper and anterior surfaces of the liver,
it is continued around its sharp margin on to the under surface, where it
presents the following relations: (a) It covers the under surface of the right
lobe and is reflected from the back part of this on to the right suprarenal
gland and upper extremity of the right kidney, forming in this situation the
inferior layer of the coronary ligament; a special fold, the hepatorenal ligament, is frequently present between the
inferior surface of the liver and the front of the kidney. From the kidney it
is carried downward to the duodenum and right colic flexure and medialward in front of the inferior vena cava, where it is
continuous with the posterior wall of the omental
bursa. Between the two layers of the coronary ligament there is a large
triangular surface of the liver devoid of peritoneal covering; this is named
the bare area of the liver, and is attached to the diaphragm by areolar tissue.
Toward the right margin of the liver the two layers of the coronary ligament
gradually approach each other, and ultimately fuse to form a small triangular
fold connecting the right lobe of the liver to the diaphragm, and named the
right triangular ligament of the liver. The apex of the triangular bare area
corresponds with the point of meeting of the two layers of the coronary
ligament, its base with the fossa for the inferior vena cava. (b) It covers the
lower surface of the quadrate lobe, the under and lateral surfaces of the
gall-bladder, and the under surface and posterior border of the left lobe; it
is then reflected from the upper surface of the left lobe to the diaphragm as
the inferior layer of the left triangular ligament, and from the porta of the liver and the fossa for the ductus venosus to the lesser
curvature of the stomach and the first 2.5 cm. of the duodenum as the anterior
layer of the hepatogastric and hepatoduodenal
ligaments, which together constitute the lesser omentum.
If this layer of the lesser omentum be followed to
the right it will be found to turn around the hepatic artery, bile duct, and
portal vein, and become continuous with the anterior wall of the omental bursa, forming a free folded edge of peritoneum.
Traced downward, it covers the antero-superior
surface of the stomach and the commencement of the duodenum, and is carried
down into a large free fold, known as the gastrocolic
ligament or greater omentum. Reaching the free margin
of this fold, it is reflected upward to cover the under and posterior surfaces
of the transverse colon, and thence to the posterior abdominal wall as the
inferior layer of the transverse mesocolon. It
reaches the abdominal wall at the head and anterior border of the pancreas, is
then carried down over the lower part of the head and over the inferior surface
of the pancreas on the superior mesenteric vessels, and thence to the small
intestine as the anterior layer of the mesentery. It encircles the intestine,
and subsequently may be traced, as the posterior layer of the mesentery, upward
and backward to the abdominal wall. From this it sweeps down over the aorta
into the pelvis, where it invests the sigmoid colon, its reduplication forming
the sigmoid mesocolon. Leaving first the sides and
then the front of the rectum, it is reflected on to the seminal vesicles and
fundus of the urinary bladder and, after covering the upper surface of that viscus, is carried along the medial and lateral umbilical
ligaments on to the back of the abdominal wall to the level from which a start
was made.