Peritoneum tutorial

okay we're now going to talk about the

peritoneum and answer the what questions

what is peritoneum in its parts

peritoneal fluid and mesothelium what is

the difference between intra and

retroperitoneal organs and what provides

innervation and vascular supply to the

peritoneum hello everyone my name is dr.

morton and i'm the noted anatomist so

here we have in this schematic a picture

of the trunk and the orange line

represents the diaphragm and above the

diaphragm are three serous sacs we have

the pericardial sac containing the heart

and then flanking either side of the

pericardial sac are two pleural sacs

both containing the lungs and below the

diaphragm is the peritoneal sac

engulfing abdominal pelvic organs and

that's what we're going to talk about

and so the abdominal pelvic cavity is

lined with a serous membrane called the


and the peritoneum completely or

partially lines the internal surface of

the abdominal wall and organs of the

abdominal cavity so let's do some

discussion of some of this jargon so

first of all what is a serous membrane

well serous membrane lines the wall in

organs of a body cavity and make serous

fluid so this picture shown here is a

cross-section through the abdominal

cavity so that's the serous membrane

we're going to talk about and so in pink

there's the serous membrane lining the

abdominal cavity and it makes fluid and

because this is the abdominal cavity

it's going to be peritoneal fluid which

then goes within the peritoneal cavity

the space or cavity within the serous

membrane and fills it

so what's mesothelium well if we now

take a little section like this like

that and blow it up that's mesothelioma

it's the tissue that comprises the

serous membrane and makes the peritoneal

fluid that goes in the peritoneal cavity

so what is peritoneum

well Greek for peritoneum means

stretched around and so the peritoneum

is the serous membrane that stretches

around or lines the abdominal cavity and

it's made of mesothelial tissue so there

in blue we just outlined or the lining

of this serous membrane that stretches

and wraps around the inside of the

abdominal cavity and organs

well the peritoneum is like a fist in a

balloon so there's a balloon and inside

the balloon is air and outside the

balloon or lining the balloon is plastic

and there's a fist

now watch Shing Shing Shing I'm gonna

ask a question is the fist in the

balloon and the answer is no what the

what because what happens now is we see

that inside the balloon is air but look

if we trace along the outside of the

balloon and see the fist going inside

the fist is not in the air the fist

simply pushed in the side of the balloon

and is covered in plastic okay so the

peritoneum is like a fist in a balloon

where there's a balloon and there's the

peritoneal cavity there's a fist and

there's the GI tract and so if we then

do this

she ching-ching notice that the

following is the GI tract in the

peritoneal cavity the answer is no why

well there's our mesothelioma sure

lining the outside and the Museo Thiele

tissue you'll notice and then notice the

peritoneal fluid the GI tract is not in

the fluid the GI tract simply pushed in

the side of the peritoneum and is

covered in mesothelium much like a fist

in the side of a balloon so what is

peritoneum well there's our peritoneal

cavity filled with peritoneal fluid and

the parietal peritoneum forms the wall

and the meze and Terry this double

membrane and the visceral peritoneum

that lines the organs and all the

parietal peritoneum

mez interior and visceral peritoneum are

all continuous with each other so what's

the difference between peritoneum and

mesothelium well distinguishing

peritoneum for mesothelioma is like

clothing and since there is a you can

classify t-shirt in two ways you can say

hey what's that made of oh it's made of


what is the name of that cotton well we

call it a t-shirt well the same way you

can classify the peritoneum in two ways

one by material and say oh that's made

of mesothelioma or by this name which is

peritoneum okay so now let's talk about

this peritoneal sac that has the

following three components parietal

peritoneum mesentery and visceral

peritoneum so the parietal peritoneum

and the word parietal means wall it's

the part of the peritoneal sac that

lines the wall and it's in contact with

the abdominal abdominal pelvic wall

there in blue and it's gonna be

innervated by somatic we're now going to

talk about the mesentery which mesentery

means middle and the primal peritoneum

when it comes around it reflects off the

posterior abdominal wall as a double

membrane like that and it transports

vessels and nerves we look at this other

cross-section in this schematic and you

see arteries and veins nerves and

lymphatics and they're coursing in this

double membrane from the posterior

abdominal wall into the gut tube into

the GI organs now the visceral

peritoneum it lines the intra abdominal

organs in the inter peritoneal space

it's also known as the serosa so there

you have it in green that's surrounding

and so when you take a look at pictures

like this often you see Oh mucosa

submucosa of them muscularis externa and

then the serosa or this of showing the

small intestine and you see all those

layers whenever you see this term serosa

that's synonymous to the visceral

peritoneum that we've just been talking


and now the peritoneal fluid that's it

there inside the cavity and its function

is to lubricate the surface of organs

and if you don't have enough fluid then

the tissues can adhere to each other in

their form adhesions and connections and

increased friction and cause scarring

and in here Ashanti adherents of tissues

now what is the volume of peritoneal

fluid it's only 50 milliliters so

there's not a lot so most of this

peritoneal space or in the peritoneal

cavity is actually it's really small and

there's only a little bit of fluid so

how much is it well there's a can of

coke that's about it diet coke that's

about it 50 milliliters or 1.7

announces of a can of Diet Coke now if

you have too much peritoneal fluid it's

called ascites and so there's normal

about 50 milliliters and ascites can be

as little as 500 milliliters which is

you know bailout if can and a half of

Diet Coke to 1500 milliliters and now

we're getting close to you know you got

almost you know a little over four cans

of Diet Coke and at times people who

have really bad ascites 35 liters and so

to give you an idea what this looks like

here's an axial CT through the abdomen

at the level of the liver and there is a

vertebra like kind of some happy faces

and dark there you can see the bottom of

the lung and there's the liver and then

there's the stomach and bright there

there's the rib and there in those red

arrows that gray that darker gray is

showing this peritoneal fluid just

filling that peritoneal space we can

cause this big swollen abdomen by having

that much fluid okay so let's talk about

the peritoneal sac peritoneal sac is

formed by the product inium in blue and

visceral peritoneum in green it's the

space between it or B basically as the

sac is formed by those and it's filled

with peritoneal fluid now here we have

in the sagittal section the following

there's our liver and there's our

stomach and there's the pancreas and the

duodenum and there's the transverse

colon and those other five green circles

are the small intestine and then behind

we have the abdominal aorta and then we

also have at the very bottom and this

infra peritoneal space we've got the

bladder the uterus and the rectum okay

so the peritoneum is shown there in blue

parietal visceral mesentery in this

sagittal section so there's our prattle

peritoneum lining the wall the Me's and

Terry the double membrane coming off

that posterior wall engulfing organs and

there's a visceral peritoneum that's

surrounding in this case one loop a

small intestine in this picture now

they're in light blue filling this

cavity there's the peritoneal sac that

contains the peritoneal cavity which is

filled with peritoneal fluid now the

peritoneal cavity has two subdivisions

the greater sac which is primarily the

majority of the space of the peritoneal


and then behind the stomach and the

liver is the lesser sac behind the

lesser omentum so here we have another

cross-section through the liver and then

there's the stomach and there's the

spleen and there's our portal triad at

the free margin of the lesser omentum so

an orange surrounding the wall is the

prata peritoneum and in purple is the

visceral peritoneum and then in blue

there we've got this peritoneal cavity

that's filled with peritoneal fluid now

the peritoneal cavity has two

subdivisions the greater sac which is

the majority of the peritoneal cavity

but deep to the stomach we've got this

lesser sac right there and so basically

the greater sac plus the lesser sac

equals the peritoneal cavity and so the

lesser sac is really just the space deep

to the stomach and lesser omentum and a

little bit of the liver now to this the

communication between the greater and

lesser sac is through an opening called

the epiploic foramen of Winslow and it's

right there we're in a long deep to that

free border of the portal triad of the

lesser omentum we also call that part of

the lesser omentum that he padded wanna

ligament which I'll talk about more in a

few minutes

so the greater omentum is part of this

peritoneal sac a part of the peritoneum

that is this apron like fold of

peritoneum and attaches between the

stomach and transverse colon primarily

and it has four layers and so there we

have this apron like peritoneum that

drapes over the much of this the

intestines and organs of the of the

abdominal cavity and attaches to the

stomach here and then also to the

transverse colon there and together it

now makes this greater omentum now

anatomist we like to name everything and

so there's really three different parts

to the greater omentum the biggest part

is the part that goes between the

stomach and transverse colon hence the

name gastro stomach colic colon ligament

even though it's not a ligament like

bone it just attaches this means into

this parrots name that attaches stomach

to transverse colon this picture doesn't

show the gastro splat

neck ligament and the gastro phrenic

ligament the parts of the greater

omentum that goes between the stomach

and the spleen and the stomach and the

diaphragm and it has four layers so

basically there's two layers that come

from the front and back of the stomach

and two layers that come from the front

and back Ravel enveloping the transverse

colon so this major part of the greater

omentum has four layers in this picture

what we see is the following

there's the greater omentum in yellow

and so there is our stomach and then it

also attaches to our transverse colon

that you can see on either side now

let's do the following let's now outline

and remove that part of the greater

omentum and we see these blood vessels

that are in there the gastro mental

arteries and veins you don't see the

veins we see the arteries of the right

and left gastro mental arteries that

supply the greater curvature of the

stomach and the greater omentum and it's

also called the gastroepiploic artery

zand veins because this term epiploic or

eppley means to float upon because the

greater momentum when the first

anatomist first opened up the abdominal

cavity we see this big apron floating

upon or looking like it's floating upon

the intestines and that's why they call

the vessels grant gastroepiploic gastro

for stomach epiploic for omentum okay so

now let's talk about the lesser omentum

and so the lesser omentum is a double

layer of peritoneum that attaches

between the stomach duodenum and the

liver and so there is this double layer

between the stomach in the liver in this

sagittal section and then it attaches

between the liver and the stomach so

let's take a look at a different view

here okay this anterior view so there's

our liver and there's the stomach and

there's the duodenum and just for

orientation there's the spleen okay and

so there I've now added since the

picture shows that the lesser omentum

dissected open

there's the lesser omentum she now the

lesser omentum has two components and so

the two parts of the lesser omentum are

called the hepatic duodenal and the

apado gastric ligaments so that dotted

line separates and so the part of the

lesser omentum that goes but

the liver in the duodenum is called

hepato - odd a duodenal ligament and the

part that goes during the liver in the

stomach is called the hip had a gastric

ligament now why do we make a

distinction between these two

well that hepatic Donnell ligament

houses three very important structures

that we called it together the portal

triad the hepatic arteries the bile

ducts and hepatic portal veins we call

those three things the portal triad and

there and then this the free margin on

the right side of the lesser omentum and

below that or deep - that is the

epiploic foramen going into the lesser

sac okay so now dissolve that out of the

way and we see these blood vessels

within the lesser omentum those are the

gastric arteries and veins are going

along the lesser curvature so I think of

gastric arteries and veins on the lesser

curvature of the stomach the lesser name

for the lesser curvature and the gastro

omental arteries and veins the greater

name for the greater curvature of the

stomach all right now describe how the

female peritoneal cavity is different

from the male all right to do that so

here basically in a nutshell the female

peritoneum has two openings and the male

peritoneum does not so here is in the

female we see the peritoneal sac and at

the bottom of the peritoneal sac are

these two openings now in the male and

we take a look at the peritoneal sac

there are no openings and so if we take

a sagittal section of that and blow it

up if we look on the lateral pelvic wall

there is one of those openings okay one

opening on this side because it's agile

the other open you need to be on the

other side and so if we now take this

little section and blow it up this is

what it's going to look like and we have

this peritoneum lining the top of the

pelvic cavity and then there is that

opening it's very small it's less than a

millimeter in diameter and there's a

uterine tube ovary and uterus to help

give some orientation and there's our

peritoneal cavity now in this sagittal

section it's that same space as showing

that peritoneal cavity lining okay and

so if we now go into here

the female peritoneum has an opening on

either side and there it is

now the purpose is for the following

when an egg in the ovary when the egg is

ovulated from the ovary it's going to

burst through the peritoneum into the

peritoneal cavity like that so now the

egg is in the peritoneal cavity and that

egg needs to get into the uterine tube

to go into the endometrium of the uterus

and so what happens is the egg moves

back into the uterine tube via the

opening in this pea female peritoneum

and now it's in the lumen and is able to

go to the endometrium of the uterus okay

all right now what is the innervation of

the peritoneum so here we have this

cross-section again and there's our

parietal peritoneum

now notice then yellow is this

intercostal nerve coursing within the

walls seg mentally all the way from and

as well you know from thoracic and

abdominal cavities and this intercostal

nerve knot gives sensation to the

overlying skin seg mentally but also is

going to seg mentally provide sensory

innervation to the Prato peritoneum

so Bridal peritoneum has somatic

sensation via the intercostal nerves and

somatic sensation means pain temperature

touch vibration key to this is pain

vibration and so if there's inflammation

that's it's gonna be a sharp localized

pain and so let's take a look and see if

that represents some type of a painful

sensation or any type of sensation then

that sensation course is along the

intercostal nerve and goes to the spinal


now there's also some somatic sensation

for the diaphragmatic Bridal peritoneum

that's different

because it's more like along the bottom

of the diaphragm that part of the Prado

pear team it's far away from the

abdominal wall it's somatic sensation is

via the phrenic nerves and so there's

our diaphragm and then there's our

peritoneal sac and the phrenic nerves

arise from the c3 c4 and c5 spinal cord

level see 3 4 & 5 keep the diaphragm

alive so they come down and they provide

motor innervation to the diaphragm but

they also appears through the diaphragm

and as you can see goes to the


and provide sensory innervation of the

diaphragmatic portion of the parietal

peritoneum in the house that Jack built

no the visceral peritoneum gets it's

visceral sensation in a lot of these

stretch receptors and such by visceral

sensory neurons since these are visceral

sensory there is no pain receptors or

somatic sensation in these traveling in

these neurons and so visceral apparent

neurons they course along blood vessels

within the double-layer mesentery and

then they course all the way back and

follow visceral a Ference back to the

appropriate spinal cord levels or

brainstem levels what okay let's talk

about the peritoneum in its vascular

supply so where's the aorta in relation

to the peritoneum the answer in the

retroperitoneal space now the two

layered mesentery transports arteries

and veins and lymphatics and autonomics

from the retroperitoneal space into the

double layered musin terry and then to

supply the visceral peritoneum as well

as the organs contained therein now

define the terms retroperitoneal and

intraperitoneal and list the organs that

fall under each of these categories okay

so where is this retroperitoneal space

and what is it well this word prefix

retro means behind and peritoneal means

the peritoneum so we look over here we

go okay there's the peritoneum outlined

in blue and in yellow that's the

retroperitoneal space which is behind

the peritoneum

and within that retroperitoneal space

are retroperitoneal organs and so organs

are considered retroperitoneal if they

have peritoneum on their anterior side

only she on the anterior side only are

not suspended by mesentery

there's the mesentery no mesentery and

lie between the parietal peritoneum and

abdominal wall prattle peritoneum and

abdominal wall so if it lists if of all

of these three conditions are met then

an organ is considered retroperitoneal

what organs does the retroperitoneal

space contain sad pucker that's what it

contains and so what is that well sad

pucker is an acronym

4's super anal glands a a Orden IVC d

the duodenum second third and fourth

parts then P for the pancreas the head

neck and body you for the ureters C for

colon specifically a sending and

descending K for kidneys

efore esophagus and R for rectum darnell

killed them now what do want to make an

a mention here that most surgeons do not

consider the ascending and descending

colon as retroperitoneal surgeons muslim

consider these as intraperitoneal

because they the way they move and

within the abdominal cavity is more like

an intraperitoneal organ so even though

in embryology in most Anatomy texts we

talk about how the ascending and

descending colon or retroperitoneal in

reality they don't function that way all

right now what is an intraperitoneal

organ well the word intra means inside

and peritoneal means peritoneum so we

take a look at the peritoneal cavity and

Shing there's an organ inside the

peritoneal cavity and organs are

considered intraperitoneal if they

reside within the peritoneal cavity

check and are suspended by mesentery

check so those are the two factors that

consider if an organism true peritoneal

or not now what organs does

intraperitoneal does the inter

peritoneal space contain the answer to

that is salty Spurs or salted pardon me

salted Spurs now what does the acronym

salted Spurs meanwhile asses for stomach

a is for the appendix L is for liver

t is for transverse colon and D is for

duodenum the key to this is it's only

the first part of the duodenum that do

Audino bulb or duodenal cap the part

that's right after the pylorus and then

the S stands for small intestines

specifically jejunum and ileum the P is

for pancreas but only the tail the tip

of the tail that touches the spleen the

rectum but only the upper third the

spleen has just mentioned and the

sigmoid colon so that acronym of salted

Spurs is the acronym to tell you what

organs are considered intraperitoneal

all right so now may I please make a

small d2

or with regards to intraperitoneal

organs so here we have that

cross-section again of the abdomen and

blue the peritoneum now let's take a

section as if you're dissecting or

during surgery and you open up the

abdominal cavity so now you're looking

inside and you see that organ and you

see the fluid in the peritoneal cavity

now remember this fist in the balloon

analogy well there's the fist and

there's the air in the balloon the fist

is not inside the balloon

the fist simply pushed in the side of

the balloon and is covered in plastic

the intraperitoneal organs are not

inside the peritoneal cavity the organ

simply pushed in the side of the

peritoneal sac and is now covered in

visceral peritoneum

so here's an intraperitoneal organ

there's a retroperitoneal organ if you

follow the fashion within they're

actually in the same fashion planes when

you see an intraperitoneal organ even

you open up the abdomen it's not in the

cavity even though we call it an

intraperitoneal organ it's all contained

within this sac okay

alright now let's talk about the

peritoneum in a nutshell

all right so there's parietal peritoneum

that lines the wall the mesentery a

double membrane that goes to the

visceral peritoneum and there we have

all three and the behind the prado

peritoneum are retroperitoneal organs

and we remember that as sad pucker and

then the within the visceral peritoneum

we have intraperitoneal organs and

remember all those organs assaulted

Spurs and that my friends is the

peritoneum in a nutshell