ICL 4.1: Peritoneum and Major Vessels of the Abdomen

Question 1

what is the peritoneum?

Answer 1

serous membrane that line the inner surface of the abdominal cavity and reflects on the abdominal viscera to cover them

Question 2

what is the parietal peritoneum?

Answer 2

the part of the peritoneum that lines the abdominal and pelvic walls

Question 3

what is the visceral peritoneum?

Answer 3

covers abdominal and pelvic organs either partly or completely

viscera partly covered by peritoneum simply raise the peritoneum from the abdominal wall, whereas the completely covered viscera are contained within peritoneal folds connecting them to the abdominal wall or to other viscera

Question 4

what is the peritoneal cavity?

Answer 4

potential space between the parietal and visceral peritoneum that usually containing a small amount of fluid; there’s nothing in side it!

it’s a closed space in males but it communicates with the exterior in females through the opening of the uterine tubes

intraperitoneal structure doesn’t mean it’s in the peritoneal cavity, it just means it’s totally covered by peritoneum

Question 5

what are the functions of the peritoneum?

Answer 5

1. it minimizes friction, resists infection, and stores fat
2. allows free movement of the abdominal viscera
3. in response to injury or infection (peritonitis), it exudes fluid and cells and tends to wall off or localize infection

Question 6

what is the omentum?

Answer 6

a fold connecting the stomach to another viscera

Question 7

what are the greater vs. lesser omentum?

Answer 7

greater omentum = a peritoneal fold connecting the greater curvature of the stomach to the transverse colon.

lesser omentum = a peroneal fold connecting the lesser curvature of the stomach to the liver

Question 8

what are the parts of the peritoneum attached to the stomach that aren’t omentum?

Answer 8

there are some peritoneal folds attached to he stomach called ligaments, not omentum

they include:
1. gastrophrenic ligament

2. gastrosplenic ligament
3. gastrocolic ligament

these ligaments are not true ligaments, they are merely double-layered folds of peritoneum

Question 9

what is the gastrophrenic ligament?

Answer 9

a peritoneal fold connecting the greater curvature of the stomach to the under surface of the diaphragm

Question 10

what is the gastrosplenic ligament?

Answer 10

a peritoneal fold connecting the greater curvature of the stomach and the hilum of the spleen

Question 11

what is the gastrocolic ligament?

Answer 11

a peritoneal fold connecting the greater curvature of the stomach to left colic flexure

Question 12

what is the mesentery?

Answer 12

a fold of peritoneum connecting the intestine (any part) to the posterior abdominal wall viscera

it has a fatty connective tissue core in which blood vessels, nerves and lymphatics travel to and from the small intestine

if an organ has a mesentery it means it’s intraperitoneal

organs with a mesentery are freely moveable!

Question 13

what is the lesser omentum? what are its 2 domains?

Answer 13

it attaches the lesser curvature of the stomach and the upper margin of the first part of duodenum to the margin of the fissure of ligamentum venosum and porta hepatis of the liver

it’s subdivided into 2 ligaments = hepatogastric and hepatoduodenal ligaments

it forms part of the anterior wall of the lesser sac

Question 14

what is the free margin of the lesser omentum?

Answer 14

the right free margin of the lesser omentum contains the portal triad = bile duct, proper hepatic artery and portal vein

the free margin of the lesser omentum forms the anterior wall of the opening to the lesser sac (epiploic foramen)

Question 15

what is the greater omentum? what are its 3 domains?

Answer 15

it attaches the greater curvature of the stomach to the posterior abdominal wall

it is a long, wide sheet of peritoneum covering almost the entire abdominal cavity like an apron

it’s subdivided into 3 ligaments = gastrophrenic, gastrosplenic, and gastrocolic ligaments

It forms the anterior and posterior walls of the inferior recess of the lesser sac (omental bursa)

Question 16

where is the root of the mesentery located?

Answer 16

the root of the mesentery (about 15 cm long) extends from the duodenojejunal flexure (above and to the left) to the ileocolic junction (below and to the right)

it crosses the 3rd part of duodenum, aorta, IVC, right gonadal vessels, right ureter and right psoas major muscle

Question 17

what is the transverse mesocolon?

Answer 17

a double layer of peritoneum which attaches the transverse colon to the posterior abdominal wall and anteriorly to:
left kidney, anterior surface of pancreas, superior mesenteric vessels, 2nd part of duodenum, and right kidney

it contains fat, blood vessels (middle colic artery and veins), lymphatics and nerves

Question 18

what are the subdivisions of the peritoneal cavity?

Answer 18

1. the greater sac
2. the lesser sac (omental bursa)

the greater sac and lesser sacs communicate through the opening to the lesser sac = epiploic or omental foramen

Question 19

what is the lesser sac?

Answer 19

a subdivision of the peritoneum that is a diverticulum or pouch of the greater sac

the lesser sac has superior recess and inferior recesses

Question 20

what are the borders of the lesser sac?

Answer 20

anterior wall: it lies behind the qaudate lobe of the liver, lesser omentum, stomach and the anterior two layers of the greater omentum

posterior wall: is formed by the peritoneum covering the diaphragm, the upper part of the left kindney and left suprarenal gland, pancreas, and the posterior two layers of the greater omentum

left margin: is formed of the spleen, gastrosplenic and splenorenal (lienorenal) ligaments

Question 21

what is the opening to the lesser sac?

Answer 21

aka epiploic or mental foramen

the opening that connects the greater and lesser sacs

it is located behind the right free margin of the lesser omentum

Question 22

what are the boundaries of the opening to the lesser sac?

Answer 22

anterior: the right free border of the lesser omentum, containing bile duct, proper hepatic artery, portal vein
inferiorly: superior surface of the first part of duodenum
superiorly: caudate process of the liver
posteriorly: IVC

Question 23

how does the peritoneal cavity develop? specifically the lesser and greater sacs?

Answer 23

there is a dorsal mesentery connecting the posterior abdominal wall to the stomach and a ventral mesentery connecting the stomach to the liver and anterior abdominal wall

the ventral mesentery between the stomach and the liver forms the lesser sac which the part between the liver and anterior wall forms the falciform ligament

the dorsal mesentery forms the greater sac

Question 24

what are intraperiotneal organs?

Answer 24

they are covered with visceral peritoneum throughout except at sites where the mesentery attaches

intraperitoneal organs are mobile

examples: small intestine, transverse colon, spleen and liver

Question 25

what are retroperitoneal organs?

Answer 25

they are covered with visceral peritoneum on one or more sides

they do NOT have a mesentery and are immobile

there are primary and secondary retroperitoneal organs

examples: kidneys, ascending and descending colon

Question 26

what are primary retroperitoneal organs? what are some examples of them?

Answer 26

this means the structures were retroperitoneal during the entirety of their development

1. adrenal glands
2. kidneys
3. ureter
4. aorta
5. inferior vena cava
6. esophagus (thoracic part, part inside abdominal cavity is intraperitoneal)
7. rectum (lower third is extraperitoneal)

Question 27

what are secondary retroperitoneal organs? what are some examples of them?

Answer 27

this means that the structures initially were suspended in mesentery aka they were intraperitoneal early on during development, then their mesenteries were absorbed into the posterior abdominal wall, pulling them behind the peritoneum during development

1. head, neck and body of the pancreas (but not the tail)
2. duodenum (except for the proximal first segment, which is intraperitoneal)
3. ascending and descending portions of the colon (but not the transverse colon, sigmoid or the cecum)
4. upper 2/3 of the rectum

Question 28

what are the 2 peritoneal compartments?

Answer 28

1. supracolic
2. infracolic

the projecting transverse mesocolon incompletely divides the peritoneal cavity into:

1. supracolic compartment above
2. infracolic compartment below

Question 29

how is the supracolic compartment of the peritoneal divided?

Answer 29

the supracolic compartment is divided into right and left subphrenic spaces by the facliform ligament

each of the right and left subphrenic spaces is further subdivided into superficial and deep spaces

1. the right superficial subphrenic space lies between the diaphragm and anterior surface of the right lobe of liver, and limited superiorly by the anterior layer of coronary ligament
2. the right deep subphrenic space lies between the liver the right kidney, hepatorenal or subhepatic space, and limited superiorly by the posterior layer of coronary ligament. It communicates inferiorly with the right paracolic gutter
3. left superficial subphrenic space: between the diaphragm anterior surface of the left lobe of the liver and anterior surface of the stomach
4. left deep subphrenic space is the omental bursa. It comminucate with hepatorenal (subhepatic) space through omental foramen

Question 30

how is the infracolic compartment of the peritoneal divided?

Answer 30

the infracolic compartment is further subdivided by root of the mesentery into 4 paracolic gutters

1. right medial paracolic gutter (right paramesenteric gutter)
2. right lateral paracolic gutter
3. left medial paracolic gutter (left paramesenteric)
4. left lateral paracolic gutter

with the exception of the right medial paracolic (right paramesenteric) gutter, all other three gutters communicate with the pelvic cavity, i.e., fluid collection in these gutters can trickle down to the pelvic cavity

Question 31

what is the blood supply of the abdominal viscera?

Answer 31

1. celiac artery
2. superior mesenteric artery
3. inferior mesenteric artery

all are branches of the abdominal aorta and are unpaired arteries

Question 32

what is the celiac artery? what are its branches?

Answer 32

it is the artery of the embryonic foregut and supplies the abdominal viscera

it arises from the abdominal aorta immediately below the aortic opening of the diaphragm (T12)

1. left gastric artery
2. splenic artery
3. common hepatic artery

Question 33

what is the route and branches of the left gastric artery?

Answer 33

it’s a branch of the celiac artery which originates from the abdominal aorta

runs over the lesser curvature of the stomach between the two layers of the lesser omentum and ends by anastomosing with the right gastric branch of the proper hepatic

branches:
1. gastric branches

2. esophageal branches

Question 34

what is the route and branches of the splenic artery?

Answer 34

it’s a branch of the celiac artery which originates from the abdominal aorta

it runs a tortious course over the upper border of pancreas behind the stomach, being separated from it by the omental bursa – the terminal part passes in front of the left kidney within the lienorenal ligament where it breaks into 5-8 terminal splenic branches which enter the hilus of the spleen

branches:
1. left gastro-omental artery

2. short gastric arteries (5-8)
3. terminal splenic branches
4. pancreatic branches

Question 35

what is the route and branches of the common hepatic artery?

Answer 35

it’s a branch of the celiac artery which originates from the abdominal aorta

it runs to the right, over the superior border of the first part duodenum, below the epiploic foramen – here, it gives off the gastroduodenal branch, and become proper hepatic and enters the free border of the lesser omentum to end in the porta hepatis by dividing into right and left hepatic arteries

branches:
1. gastroduodenal artery which passes behind the first part of duodenum and ends at its lower border by dividing into right gastroomental and superior pancreaticoduodenal artery

2. supraduodenal artery

Question 36

what are the branches of the proper hepatic artery?

Answer 36

1. right gastric artery:

runs in the lesser curvature of the stomach and anastomoses with left gastric artery.

2. right hepatic artery

supplies the right lobe of the liver and gives cystic artery to the gall bladder

3. left hepatic artery: supplies qaudate, quadrate and left lobes of the liver

Question 37

what are the anatomic variations associated with the celiac artery?

Answer 37

1. celiac artery may be absent and the individual branches may arise separately from aorta
2. left gastric may give off the left hepatic artery
3. common hepatic may arise entirely from the superior mesenteric

Question 38

what is the route of the superior mesenteric artery?

Answer 38

it is the artery of the embryonic midgut

it arises from the aorta 1cm below the celiac artery (L1), behind the pancreas and splenic vein

it passes downward, forward, and to the right, crossing anterior to the abdominal aorta, left renal vein , uncinated process of pancreas and horizontal part of duodenum – here, it enters the root of the mesentery and continue downward and to right crossing the inferior vena cava, right ureter, right gonadal vessels and right psoas major muscle

Question 39

what are the branches of the superior mesenteric artery and what do they supply?

Answer 39

1. inferior pancreaticoduodenal artery
2. jejunal and ileal branches
3. middle colic –> transverse colon
4. right colic –> ascending colon
5. ileocolic –> ascending colon, cecum, appendix and terminal ileum

Question 40

what is the inferior mesenteric artery?

Answer 40

this is the artery of the hind gut of the embryo

it arises 3-4 cm above the bifurcation of the aorta

it ends as it crosses the left common iliac artery by becoming the superior rectal artery

Question 41

what are the branches of the inferior mesenteric artery?

Answer 41

1. left colic –> divides into ascending and descending branches
2. sigmoidal branches
3. superior rectal –> direct continuation of the inferior mesenteric

Question 42

what is the portal venous system?

Answer 42

the hepatic portal venous system begins at the venous ends of capillaries in the organs of the GI tract and ends at the venous sinusoids in the liver

the portal vein is formed by the joining of the splenic vein with the superior mesenteric vein behind the neck of pancreas

the portal vein runs in the free margin of the lesser omentum to reach the porta hepatis where it divides into right and left branch

portal vein –> branch –> smaller branch –> capillary –> sinusoid –> RHV/LHV –> IVC

Question 43

what are the tributaries of the portal vein?

Answer 43

1. superior mesenteric vein
2. splenic vein
3. left gastric artery
4. right gastric vein
5. cystic vein end in the right branch of the portal vein
6. paraumbilical vein drains into the left branch

Question 44

what are the tributaries of the superior mesenteric vein?

Answer 44

1. veins that accompany the branches of the superior mesenteric artery
2. right gastro-omental
3. pancreaticoduodenal veins

Question 45

what are the tributaries of the splenic vein?

Answer 45

1. small splenic vein
2. left gastro-mental vein
3. short gastric veins
4. inferior mesenteric vein

Question 46

what are the sites of the port-caval anastomosis?

Answer 46

1. at the lower end of esophagu between the tributaries of the left gastric veins (portal) and tributaries of esophageal veins which drains in azygos vein (systemic)
2. at the anal canal between the tributaries of superior rectal veins, which drains into inferior mesenteric vein, which is, in turn, into splenic, and tributaries of the middle and inferior rectal veins
3. around the umbilicus between the periumbilical superficial veins drained by thoraco-epigastric vein and paraumblical veins along the round ligament (portal)
4. on the posterior abdominal wall between the intestinal tributaries of portal vein and lumbar veins (systemic)

Question 47

what is portal hypertension?

Answer 47

portal HTN occurs when portal circulation through the liver is obstructed by liver disease (cirrhosis) or tumor

the high portal pressure promotes the enlargement (varices) of alternate pathways to the caval system