Download - The Digestive System Lecture 4
The Digestive SystemLecture 5
Peritoneal Folds of Posterior
Abdominal Wall
a. Mesentery of small intestine:
▪ It is a broad, fan-shaped peritoneal fold
connecting coils of jejunum and ileum to
posterior abdominal wall.
▪ The border attached to posterior wall of
abdomen is called the root of the
mesentery, which is about 15 cm long, and
extends obliquely downwards and to the
right from duodenjejunal flexure to the
upper part of right sacroiliac joint. 1
Root of
mesentery of
small intestine
2
Mesentery of small
intestine
3
▪ The intestinal border of mesentery is about 6
m long and is thrown into numerous pleats.
▪ At this border the two layers of the
peritoneum separate to enclose the gut,
forming its visceral layer.
b. Transverse mesocolon:
▪ It is a broad peritoneal fold that connects the
transverse colon to posterior abdominal wall.
▪ Its two layers pass from anterior aspect of
head and body of pancreas to posterior
surface of transverse colon, where they
separate to enclose that part of the colon. 4
▪ Between the two layers of the transverse
mesocolon are the blood vessels, nerves
and lymphatics of the transverse colon.
5
Root of
transverse
mesocolon
6
Transverse mesocolon
7
Transverse
mesocolon
8
c. Sigmoid mesocolon:
▪ This fold connects the sigmoid colon to
pelvic wall.
▪ The line of attachment to pelvic wall has
the form of an inverted V, the apex of which
lies near the division of the left common
iliac artery.
▪ The left limb descends medial to the left
psoas major muscle.
▪ The right limb descends into the pelvis and
ends in the medial plane. 9
▪ The sigmoid and superior rectal vessels
pass between the two layers of the sigmoid
colon.
10
Sigmoid mesocolon
11
Sigmoid Mesocolon
12
d. Mesoappendix: ▪ It is a triangular peritoneal fold around the
vermiform appendix.
▪ It is attached to the back of lower end of
the mesentery, close to ileocaecal junction.
▪ Usually, it extends to tip of the appendix.
▪ The blood vessels, nerves and lymph
vessels of the vermiform appendix,
together with a lymph nodes lie between its
two layers.
13
Mesoappendix
Inferior ileocecal recess
Superior ileocecal recess
ileocecal fold
14
Lesser Omentum▪ Constitute the two layers of peritoneum
that descends from the fissure for
ligamentum venosum and porta hepatis to
the lesser curvature of stomach, and
proximal 2 cm of duodenum.
▪ Between the liver and the 1st 2 cm of
duodenum, the omentum presents a free
right border, which forms the anterior
boundary of the epiploic foramen.
15
▪ This free border contains between its two
peritoneal layers the portal vein, hepatic
artery and bile duct.
16
Lesser
omentum
17
Epiploic
foramen
18
Lesser
omentum
Common bile duct
Proper hepatic artery
Portal vein
Epiploic
foramen
19
Greater Omentum▪ It is the largest peritoneal fold, and
consists of a double sheet of peritoneum,
folded on itself to form four layers.
▪ The anterior two layers descend from
greater curvature of stomach and first 2 cm
of duodenum, pass downwards in front of
loops of small intestine for a variable
distance, and then they turns round and
ascend up to the transverse colon where
they loosely blend with the peritoneum on
the anterior surfaces of the transverse
colon and mesocolon. 20
▪ The greater is a storage house for fat.
▪ In addition, the greater omentum contains
numerous fixed macrophages, which can
be mobilized as free macrophages.
▪ These cells may accumulate in places into
dense, oval or round patches, visible to the
necked eye as 'milky spots‘ on the
omentum.
21
22
Greater omentum
(posterior fold)
Transverse
mesocolonGreater
omentum
(anterior
fold)
23Greater omentum)
Lesser Sac▪ Anterior wall: Forms by the posterior layer of
the anterior fold of greater omentum; posterior
surface of stomach; and lesser omentum.
▪ Posterior wall: Forms by the anterior layer of
the posterior fold of the greater omentum; and
posterior abdominal wall.
24A
24B
Greater omentum
(posterior fold)
Transverse
mesocolonGreater
omentum
(anterior
fold)
Lesser
sac
Peritoneal Compartments▪ The peritoneal cavity can be divided into three
compartments, supracolic, infracolic, and
pelvic.
▪ The dividing line between the supracolic and
infracolic compartments is the attachment of
the transverse mesocolon to the posterior
abdominal wall.
▪ The attachments of the liver to the diaphragm
and supraumblical part of the anterior wall of
the abdomen define the subdivision of the
supracolic compartment.
25
▪ To the right and left of the falciform
ligament are the right and left subphrenic
spaces.
▪ Behind the right lobe of the liver and in
front of the right kidney is the right
subhepatic space.
▪ Below the transverse mesocolon, the
infracolic compartment is subdivided into
right and left infracolic spaces, by the
attachment of the root of the mesentery of
small intestine.
26
Paracolic GutterThese gutters lie on lateral and medial sides
of ascending and descending colons,
respectively.
Intraperitoneal OrgansAn organ is said to be intraperitoneal when it
is almost totally covered with visceral
peritoneum. The stomach, 1st 2 cm of
duodenum, jejunum, ileum, transverse colon,
sigmoid colon, and spleen are good examples
of intraperitoneal organs.
27
Retroperitoneal OrgansRetroperitoneal organs lie behind the
peritoneum and are only partially covered
with visceral peritoneum. The pancreas,
ascending and descending colons, kidneys,
and ureters are examples of retroperitoneal
organs.
28
Nerve Supply of the Peritoneum
1. The parietal peritoneum:
▪ Is sensitive to pain, temperature, touch,
and pressure.
▪ The parietal peritoneum lining the central
part of diaphragm is supplied by the
phrenic nerve (C4) --- hence referred pain
from this area to tip of shoulder.
▪ The peritoneum lining the peripheral part
of diaphragm is supplied by the lower six
intercostals nerves. 29
▪ The remainder of the parietal peritoneum is
supplied by the lower six intercostals and
L1 nerves.
▪ In the pelvis the obturator nerve is the
chief source of supply.
2. The visceral peritoneum:
• Is sensitive only to stretch and tearing and is
not sensitive to touch, pressure, or
temperature.
. It is innervated by afferent nerves which
travel with the autonomic supply to the
viscera. 30
▪ Overdistension of a viscus leads to the
sensation of pain.
31
Stomach▪ Is the most dilated part of the
gastrointestinal tract, interposed between
end of esophagus and beginning of
duodenum.
▪ It lies in epigastric, umblical, and left
hypochondriac regions of abdomen.
▪ Its main functions is storage of food mixed
the food with gastric secretion to form a
semifluid chyme, and the controlled the rate
of delivery of chyme to the small intestine.
32
▪ It is roughly J-shaped and has two
openings, two borders, and two surfaces
33
Cardiac orifice▪ Is the opening by which esophagus
communicates with stomach.
▪ Lies on the left of median plane, behind the
7th left costal cartilage 2.5 cm from its
junction with the sternum (at the level of
T11 vertebra).
Pyloric orifice▪ Is the opening by which stomach
communicates with duodenum.
34
▪ Lies about 1.2 cm to the right of median
plane near the level of lower border of L1
vertebra (transpyloric plane), when the
body is in the supine position.
Right border (lesser curvature)▪ Continuous with right border of
esophagus.
▪ The angular incisure is a notch on this
border, nearer pylorus than esophagus.
Left border (greater curvature) Joins the left border of esophagus at an
acute angle, the cardiac notch. 35
Cardiac orifice
Pyloric
orifice
36
Anterior surfaceIs related to anterior abdominal wall, left
costal margin, left pleura and lung,
diaphragm, and left lobe of liver.
Posterior surface Is related to stomach bed (lesser sac,
diaphragm, spleen, left suprarenal gland,
upper part of left kidney, splenic artery, body
of pancreas, transverse mesocolon, and
transverse colon).
37
38
Stomach (Anterior Relations)
Greater omentum
(posterior layers)
39
Stomach (Posterior Relations)
The stomach is divided into three parts:
fundus, body and pylorus.
Fundus▪ Is dome-shaped and projects upwards and
to the left of cardiac orifice.
▪ It is usually filled with swallowed air.
BodyIs the largest part of stomach, extends from
cardiac orifice to level of angular incisure.
40
Pyloric part▪ Extends from body to pyloric orifice.
▪ It is subdivided into three regions: pyloric
antrum, pyloric canal, and pylorus.
a. The pyloric antrum:
Is the dilated proximal portion of pylorus.
b. The pyloric canal:
Is the narrow, cylindrical portion, 2 – 3 cm
long, which continues distally with pylorus.
41
c. The pylorus:
▪ Is the thickened portion of the stomach
that unites it to duodenum.
▪ The thickening is due to an increase in the
amount of circular muscle to form the
pyloric sphincter, which is concerned with
controlling the rate of discharge of stomach
contents into duodenum.
42
Pylorus
43
▪ When the stomach is empty, the mucosa
lies in large folds, called rugae.
▪ The stomach is completely enclosed by
visceral peritoneum, which leaves the
lesser curvature as the lesser omentum and
the greater curvature as the greater
omentum.
44
Arterial Supply:The arterial supply of stomach arises from
celiac trunk.
a. Right and left gastric arteries:
▪ Are branches of hepatic and celiac arteries,
respectively.
▪ They form an anastomosing arch along lesser
curvature.
b. Right and left gastroepiploic arteries:▪ are branches of gastroduodenal and splenic
arteries, respectively.
▪ They form a similar arch along the greater
curvature. 45
C. Short gastric arteries: • Branches of the splenic artery.
• They supply the fundus.
Venous Drainage▪ Veins from stomach drain into portal
circulation.
▪ The right and left gastric veins drain directly
into portal vein.
▪ The right gastroepiploic vein joins the
superior mesenteric vein.
46
▪ The left gastroepiploic and short gastric veins
join the splenic vein.
Lymph Drainage:▪ Lymph vessels from stomach follow the
arteries and drain into right and left gastric
nodes, the right and left gastoepiploic nodes,
and the short gastric nodes.
▪ Lymph from these node drains into the celiac
nodes.
47
Nerve Supply:The stomach is supply by sympathetic and
parasympathetic fibers (vagi) via the celiac
plexus.
48