Download Gastro18-GITractPt2

Checked by Dr. Roque
GI #18
Wed, 02/19/03, 2pm
Dr. Roque
Jennifer Uxer for Dustin Tauferner
Page 1 of 4
Gastrointestinal Tract Anatomy, Part II
I.
II.
III.
Duodenum—1ft (Small Intestines)
A. 1st part
 Liver, gall bladder
 Internal aspect has a c-shape, pyloric sphincter,
 Duodenal bulb—proximal section of the 1st part, no circular folds (plicae
circularis) that show up in the jejunum
B. 2nd part
 Major duodenal papilla
 This papilla contain the opening of the common bile duct and major
pancreatic duct—dump secretions in this section.
rd
C. 3 part
 Superior mesenteric artery and vein cross anteriorly to the 3rd part of the
duodenum. They are initially found behind the pancreas.
D. 4th part
 Found superiorly
 Contains the duodenal jejunal flexure, an almost 90° angle formed where the
2 join.
 Ligament of Treitz
Jejunum—8ft. (Small Intestines)
 Starts on the left side of the body and goes right
 Know the differences between the jejunum and the ileum. These are
especially important in surgery.
o There’s no strict demarcation between the 2 due to a gradual transition from
jejunum to ileum.
o So, the proximal jejunum and the distal ileum show their individual
characteristics.
o A barium swallow will show the differences: the jejunum will be feathery
looking with gaps in its lumen while the ileum will have a solid looking
lumen filled with barium.
 Bigger diameter
 Thicker walls
 Larger plicae circulares, which make thicker walls
 More vascular, darker color
 Lesser fat in mesentery
 “Windows”—areas where you can see light shining through the mesentery.
Formed because there is less fat creeping to the wall of the jejunum.
 Fewer arterial arcades (anastomoses)
 Longer vasa rectae due to fewer arcades
Ileum—12 ft. (Small Intestines)
 Found mainly in the right inguinal area
 Meckel’s diverticulum
Checked by Dr. Roque
GI #18
Wed, 02/19/03, 2pm
Dr. Roque
Jennifer Uxer for Dustin Tauferner
Page 2 of 4
o Found in 1 – 2% of the population
o Follows the Rule of 2’s
 Found in 2% of the population
 Found approximately 1-2 feet from the ileocecal junction
 Contains 2 types of mucosa: 1. gastric mucosa—can secrete acid
which causes ulcers and 2. duodenal mucosa (can also have
pancreatic mucosa containing Islets of Langerhans, which secrete
insulin)
o Can present clinically as bleeding or obstruction
o Food or intestinal contents can come out of the umbilicus if diverticulum
remains patent
 Peyer’s patches—aggregated lymph nodules in the submucosa
 More fat in the mesentery; therefore, no windows are found
 More arcades
 Shorter vasa rectae
 Distal part is almost smooth
IV. Large Intestines
A. General Features used to distinguish it from the small intestine
 Teniae coli
o Formed in sections where there is not a complete outer longitudinal
muscle layer
o See bands of muscle—teniae coli
o Not present in vermiform appendix and rectum—both have a
complete outer longitudinal muscle layer
o Useful for locating base of appendix, since the 3 teniae coli converge
at the base of the vermiform appendix.
 Haustrae coli—formed because the teniae coli are shorter than the length of
the large intestines. This causes bulges/pleats/sacculations in the intestine.
These are the haustrae coli.
 Omental (epiploic) appendages—fatty tags/adipose tissue—has lots of fat
compared to the small intestine
B. Parts
 Cecum
 Vermiform appendix
 Ascending colon
 Transverse colon
 Descending colon
 Sigmoid colon
 Rectum
 Anal canal
C. Vermiform appendix
 Mesoappendix-mesentery
 Completely peritonealized
Checked by Dr. Roque

GI #18
Wed, 02/19/03, 2pm
Dr. Roque
Jennifer Uxer for Dustin Tauferner
Page 3 of 4
No tenia coli—has a complete longitudinal muscle (way for the surgeon to
find it)
 Variable in location—retrocolic, subcecal, pelvic, retrocecal (65% of cases)
o Usually found behind the cecum because the appendix is usually short in
length
o The base, which is attached to the cecum, is in a fixed location with little
variation from person to person
o The tip can be found in different locations due to the length
o If it’s longer, it can hide behind the ascending colon making it retrocolic.
In this position, it almost touches the liver. If appendicitis develops, it
swells and can touch the liver causing an abscess.
 Base of appendix is found where 3 tenia coli converg. This can be identified
on the anterior abdominal wall as McBurney’s point. In appendicitis,
there’s usually pain and tenderness at this point. Draw a line from the
umbilicus to the ASIS and divide the line into thirds. The junction of the
medial 2/3 and lateral 1/3 is McBurney’s point.
V. Clinical Correlations
 Hypertrophy of the pyloric sphincter
o Called hypertrophic pyloric stenosis
o Common in children, especially in males
o Must be diagnosed early to correct; child spits up anything he ingests
 Ulcers
o Can be seen with a barium swallow
o Duodenal bulb is a common location
o Gastroduodenal artery is eroded by a duodenal ulcer and splenic artery can
be affected/eroded by gastric ulcers
 Omphalocoele
o Initially the intestines form outside of the embryo’s abdominal cavity due to
physiological herniation. They must move inside before the wall closes.
o Sometimes, they remain outside causing external intestinal herniation,
which must be repaired.
 Toxic megacolon
o Can be common
o Caused by absence of parasympathetic ganglia in the intestinal wall.
Because there’s no innervation, the intestines begin enlarging.
o The lack of innervation leads to absence of peristalsis which causes
obstructions.
VI. HTML Lecture Notes
 HTML lecture notes are on the schedule page of the GI web site—be sure to
look at these.
 He touched on the following in class.
 Inguinal Ligament
o Most inferior part of the external abdominal aponeurosis
o Aponeurosis curves around on itself
Checked by Dr. Roque
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GI #18
Wed, 02/19/03, 2pm
Dr. Roque
Jennifer Uxer for Dustin Tauferner
Page 4 of 4
o Muscles and vessels (i.e. psoas muscle, femoral artery and vein) pass behind
the inguinal ligament
o Runs from ASIS to the pubic tubercle
Lacunar ligament—a good site to anchor sutures when fixing an inguinal hernia
Superficial inguinal ring
o An opening—can be difficult to find, especially in females due to the
fibrous round ligament of the uterus
o See the ilioinguinal nerve exiting from this ring
Cremaster muscle—from the internal abdominal oblique muscles which are not
aponeurotic at their inferior part
Conjoint tendon
o Formed from the internal abdominal and transverse aponeurosis
o The conjoint tendon or falx inguinalis is found in front of the inguinal
triangle (Hasselbach’s triangle), formed by the rectus abdominus muscle,
inferior epigastric artery and inguinal ligament
o When it weakens, a direct hernia can result causing a bulging directly
into the anterior abdominal wall. A direct hernia may be found medial
to the inferior epigastric artery at the inguinal triangle
o In contrast, an indirect inguinal hernia enters through the deep ring, lateral
to the inferior epigastric artery.