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Human Anatomy: GI Tract
Wednesday, Feb 19, 2003 1:00 PM
Jack Sun
Dr. Roque Page 1 of 5
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GI Tract
(Announcement) Dr. Roque: He doesn’t know how many questions will be on this year’s test,
but last year there were 20 questions from the Gross Anatomy lectures. Also, there will be a lot
of changes on this year’s test. This year there will be more questions given in the form of clinical
applications. So, pay close attention to the clinical examples given in the lectures.
Understand that the peritoneum and the peritoneal cavity and its spaces are very important
because of theirclinical implications. Try to understand the relationships of the structures to
each other within the peritoneal cavity, since manifestation of disease in one organ can involve
adjacent structures/organs. Examples:
 an ulcer in the stomach can lead to pancreatitis or intrabdominal bleeding
 gall bladder disease can result in obstruction of the duodenum
Subdivisions of the Peritoneal Cavity
 Organs develop in the extraperitoneal fatty layer and protrude into the peritoneal cavity
with their mesenteries, when this occurs, new cavities/spaces are formed
 This becomes important when fluid begins to accumulate in the peritoneal cavity and
based on the position of the patient the fluid can move as well
 Peritoneal cavity can be divided into two main spaces:
o Greater sac (N329)
 This is the space you see when you open up the abdomen. It is synonymous with
the peritoneal cavity itself.
o Lesser sac or Omental Bursa (N255, N256, N257, N258, N329)
 Enclosed space that lies posterior to the stomach
o Opening that connects the Greater Sac with the Lesser Sac is known as the foramen
of Winslow or epiploic foramen
 You can put your finger here to enter the lesser sac
**Refer to the Course Website for detailed embryology review**
In Class Demonstration (Stomach Development):
 Dr. Roque got a tube with two flaps of plastic sheets attached to each side of it. The tube
represents the stomach and two flaps represent the dorsal and ventral mesentery. It
almost looks like a butterfly (the body being the tube and the wings representing the two
plastic flaps)
 He used this to demonstrate the development of the stomach and its surrounding organs.
 Development of the stomach entails two rotations
o 1st the stomach rotates clockwise such that its left border moves anteriorly together
with the vagus nerve; ventral mesentery (front plastic flap) rotates to the right and
dorsal mesentery rotates to the left.
o 2nd the stomach rotates counterclockwise on its anteroposterior axis such that the
ventral mesentery moves up together with the liver which has started to develop.
The ventral mesentery becomes the lesser omentum that connect the liver to the
stomach and duodenal bulb. The dorsal mesentery moves down folds upon itself
and attaches the digestive tube to the pancreas and the POSTERIOR ABDOMINAL
WALL. The dorsal mesentery becomes the Greater Omentum. Thespace behind the
lesser omentum is the lesser sac and the opening to it is the foramen of Winslow.
o Greater and Lesser omenta hold the stomach in its place
Human Anatomy: GI Tract
Wednesday, Feb 19, 2003 1:00 PM
Dr. Roque Page 2 of 5
Peritoneal Cavities
 Fluid can accumulate in the spaces within the peritoneal cavity (such as pus and blood)
 When the patient lies down, and fluid is poured in, the fluid will flow to the lowest
portion or “dependent portion” of the peritoneal cavity = Morrison’s pouch or
Hepatorenal pouch or recess
 This is located beneath the visceral surface of the liver and anterior to the right kidney
Hepatorenal recess
 Fluid will accumulate in this area if
the patient is bed-ridden
 Now if this patient sits up to take their
medication, any fluid in the
hepatorenal recess will now flow to
the pelvic cavity
 Clinical Correlation: If a patient is in the hospital with a liver abscess and he is lying
down a lot, when he gets up to take a walk, the fluid in his hepatorenal recess will
flow on side of the ascending colon to his pelvic cavity. Now the patient will also
present with a pelvic disease. These two problems are not isolated incidents but related
to each other because the peritoneal cavities are connected. The doctor should realize
that the abscess fluid has traveled down to the pelvic cavity.
 These spaces are presented in all people and these problems can occur in all patients
Right Medial
Paracolic gutter
Left Lateral
Paracolic gutter
Paracolic gutters
 4 total paracolic gutters
 2 on each side of the Ascending colon and the Descending colon
 Paracolic gutters around the Ascending colon are called the Right Lateral and Medial
paracolic gutters
 Right Lateral paracolic gutter is on the outside of the ascending colon
 Paracolic gutters around the Descending colon are called the Left Lateral and Medial
paracolic gutters
 Any fluid that accumulates in the Right Medial paracolic gutter will stay in place and
cause abscess because it is blocked by ileum, parts of the colon and the greater omentum
anteriorly.
o This will have similar symptoms compared with a appendicitis, but it will present
with a different history
Human Anatomy: GI Tract
Wednesday, Feb 19, 2003 1:00 PM
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Peritoneum
 Parietal peritoneum – lines the peritoneal cavity (it covers the space)
 Visceral peritoneum – forms the serosal layer of the organs
 When the organ pushes through the parietal peritoneum and wraps itself around it that
peritoneum then becomes the visceral peritoneum
 When the organ protrudes through the peritoneum, the peritoneum also forms a stalk that
carries the blood and nerve supply to the organ; therefore, if you cut this stalk the organ
will die
 Stalk is the communicating line between the visceral and parietal peritoneum, and is
named according to its location.
Derivatives of the Peritoneum
 Connect visceral organs to each other, to abdominal walls, and to diaphragm
 Convey blood vessels and nerves to each other
 They include Mesentery and Omentum and Peritoneal ligaments
Posterior part of the Anterior Abdominal Wall
 Umbilicus
 Falciform ligament will connect to the liver
o Free end contains the Ligamentum Teres Hepatis (or Round Ligament of the Liver)
 Median umbilical fold
o Passes from the umbilicus to the apex of the urinary bladder
o Contains the median umbilical ligament
 Umbilical ligament is the remnant of the urachus – fibrous remnant of the allantois
 If it remains patent after birth, leakage of urine from the umbilicus can be seen,
especially in children
 Two medial umbilical folds on each side of the median umbilical fold
o Remnants of the umbilical arteries
o Umbilical cords contain two arteries and one vein (vein is superior and two arteries
are inferior) -- they remain open at birth
o This is important because exchange or blood transfusions might be needed
o Remember, in the fetus, umbilical arteries carry unoxygenated blood and umbilical
veins carry oxygenated blood
 Lateral umbilical folds
o They contain patent blood vessels: Inferior epigastric arteries and veins going to the
posterior aspect of the rectus abdominis
o Only the lateral umbilical folds contain patent vessels
Dr. Roque continued with the second part of the Gastrointestinal Tract Lecture Here.
(Lecture will start with the stomach since we covered the mounth though the esophagus during
the Cardiopulmonary System)
Stomach
 Know the different parts of the stomach (N258, N259)
o Cardia
Human Anatomy: GI Tract
Wednesday, Feb 19, 2003 1:00 PM
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o
o
o
o
Fundus
Body
pyloric part
pyloric sphincter
 Know the structures that form the bed of the stomach
o Important because of ulcers
o Ulcers commonly occur in the body of the stomach and may be found in the posterior
wall
o Anytime an ulcer erodes through the wall, the contents of the stomach will spill into
the lesser sac and the bed of the stomach
o Lesser Sac is the space that the stomach bed occupies, this is where the spilled
content will be found
 Contents of the Stomach Bed (N255, N256)
o Spleen
o Splenic Artery – artery most likely to be affected by posterior perforation of a
gastric ulcer
 This can result in internal abdominal bleeding and patient can go into shock
o Left kidney
o Pancreas – organ most likely to be affected in case of a perforating ulcer
 Clinical Vignette: A patient with a history of gastric ulcers suddenly presents
with a different type of pain radiating to the back with elevation of amylase and
lipase, and vomiting of blood, the patient has developed pancreatitis
o Diaphragm
o Left supernal gland
o Transverse mesocolon
o Posterior wall of omental bursa
 Curvatures of the Stomach (N258)
o Lesser curvature
 Continuous with RIGHT border of esophagus
 Mesentery attached to the lesser curvature is called Lesser Omentum
 Connects the lesser curvature to the 1st part of the liver and duodenum
 Contains the common bile duct, hepatic artery proper and portal vein
 Found posterior to the left lobe of the liver
 Lesser Omentum is divided into two parts
 Hepatogastric ligament – connects the stomach to the liver
 Hepatoduodenal ligament – connects the stomach to the duodenum
** If you were to put your finger behind the hepatoduodenal ligament, the space you
would enter would be the foramen of Winslow. Your finger will be behind the lesser
omentum and the space will be the lesser sac
o
Greater curvature
 Continuous with LEFT border of esophagus
 Mesentery attached to the greater curvature is called the Greater
Omentum
 Connects greater curvature to the transverse colon, spleen, and
diaphragm
 Function is to limit peritoneal infections
Human Anatomy: GI Tract
Wednesday, Feb 19, 2003 1:00 PM
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


Gastrocolic ligament – connects stomach to transverse colon
Gastrosplenic (gastrolienal) ligament – connects stomach to spleen
Grastrophrenic ligament – connects stomach to diaphragm
**Dr. Roque said don’t worry about the peritoneal ligaments, except for those in the
posterior aspect of the anterior abdominal wall**
 Internal Features of the Stomach (N259)
o Cardiac Orifice
o Rugae are the gastric ridge/ folds/ elevations
o Gastric pits are the valleys between the folds
 Opening of the gastric glands are located in the gastric pits
 Muscle Layers of the Stomach
o Outer layer – longitudinal muscle
 Runs mostly in the greater and lesser curvatures of the stomach
o Middle layer – circular muscle (in the pylorus, forms the pyloric sphincter)
o Inner layer – oblique (This layer is found only in the Stomach)
In the rest of the gastrointestinal tract there are only the OUTER longitudinal layer and
INNER circular layer (for example in the small and large intestines)
Duodenum (N261)
 C shaped Structure (1 ft long)
 Divisions of the Duodenum (N253, N261, N262)
o 1st part (superior part)
 In direct continuity with the pylorus
 It can be divided into two parts (Duodenal Bulb is the proximal half of the first
part of the duodenum)
 Duodenal ulcers occur mostly in the duodenal bulb
 Gall Bladder is found anteriorly to 1st part of the duodenum
 Clinical Vignette: If a patient has a gall bladder stone and it gets inflamed
and perforates posteriorly, the stones can get inside the duodenum. If the
stone is large enough, it can obstruct the duodenum.
 It also stains the anterior surface of the duodenum postmortem
 Neck of the pancreas is located inferiorly
 Hepatoduodenal ligament attached to the duodenal bulb
o 2nd part (descending part)
 Lots of ridges/ circular folds called Plicae Circularis found here
 This is beneficial because it increases the surface area for absorption of food
 Major duodena papilla is found in this region
 It contains the hepatopancreatic ampulla formed by the union of the
common bile duct and pancreatic duct
 Site of bile release and pancreatic enzyme release into the small intestines
o 3rd part (inferior, horizontal part)
 superior mesenteric artery and vein cross in front of the 3rd part
o 4th part (ascends superiorly)
 connects to the jejunum at the duodenojejunal flexure