WHAT IS MECKEL’S DIVERTICULUM?
Meckel’s diverticulum is a congenital anomaly representing a persistent portion of the vitellointestinal
duct. It is located (if present) on the antimesenteric border of the ileum approximately 2 ft. (60 cm) from
the ileocecal junction. It is about 2 in. (5 cm) in length, and it occurs in approximately 2% of individuals.
It is important clinically because bleeding may occur from an ulcer in its mucous membrane.
WHAT IS CROHN DISEASE ?
Crohn disease (CD) is a chronic inflammatory bowel disease that most commonly affects the ileum and
involves an abundant accumulation of lymphocytes forming a granuloma (a typical feature of CD)
within the submucosa that may further extend into the muscularis externa. Neutrophils infiltrate the
intestinal glands and ultimately destroy them leading to ulcers.
With progression of CD, the ulcers coalesce into long, serpentine ulcers (“linear ulcers”) oriented along
the long axis of the bowel. A classic feature of CD is the clear demarcation between
diseased bowel segments located directly next to uninvolved normal bowel and a cobblestone
appearance that can be seen grossly and radiographically. The etiology of CD is unknown. Clinical
findings include intermittent bouts of diarrhea, weight loss, and weakness. Complications include
strictures of the intestinal lumen, formation of fistulas, and perforation.
Epidemiology More common in whites vs. blacks
More common in Jews vs. non-Jews
More common in women
Affects young adults
Extent Transmural
Location Terminal ileum alone (30%)
Ileum and colon (50%)
Colon alone (20%)
Involves other areas of GI tract (mouth to anus)
Gross Features Thick bowel wall and narrow lumen (leads to obstruction)
Aphthous ulcers (early sign)
Skip lesions, strictures, and fistulas
Deep linear ulcers with cobblestone pattern
Fat creeping around the serosa
What is Ulcerative colitis?
Ulcerative colitis is a type of idiopathic inflammatory bowel disease. It always
involves the rectum and extends proximally for varying distances. The inflammation is continuous,
that is, there are no “skip areas” as in CD. The etiology of ulcerative colitis is unknown. Clinical
signs include bloody diarrhea with mucus and pus, malaise, fever, weight loss, anemia, and may
lead to toxic megacolon.
Epidemiology More common in whites vs. blacks
No sex predilection
Affects young adults
Extent Mucosal and submucosal
Gross Features Inflammatory pseudopolyps
Areas of friable, bloody residual mucosa
Ulceration and hemorrhage
Location Mainly the rectum
May extend into descending colon
May involve entire colon
Does not involve other areas of GI tract
Clinical Findings Recurrent left-sided abdominal
cramping with bloody diarrhea and mucus
what is small intestine?
Small Intestine
The greater part of digestion and food absorption occurs in the small intestine, which extends from the
pylorus of the stomach to the ileocecal junction . The small intestine is divided into three
parts:
the duodenum,
the jejunum,
and the ileum.
WHAT IS DUODENUM?
The duodenum is a C-shaped tube approximately 10 in. (25cm) in length that curves around the head of
the pancreas
The duodenum begins at the pyloric sphincter of the stomach, and it ends by becoming continuous with
the jejunum. The first inch of the duodenum has the lesser omentum attached to its upper border and the
greater omentum attached to its lower border. The remainder of the duodenum is retroperitoneal.
The duodenum is divided into four parts:
• The first part runs upward and backward on the transpy-
loric plane at the level of the first lumbar vertebra.
• The second part runs vertically downward. The bile and the main pancreatic ducts pierce the medial
wall approximately halfway down, and they unite to form an ampulla that opens on the summit of a
major duodenal papilla
The accessory pancreatic duct (if present) opens into the duodenum on a minor duodenal papilla,
approximately 0.75 in. (1.9 cm) above the major duodenal
papilla.
• The third part passes horizontally in front of the vertebral column. The root of the mesentery of the
small intestine and the superior mesenteric vessels cross this part anteriorly.
• The fourth part runs upward and to the left to the duodenojejunal flexure. The flexure is held in
position by the ligament of Treitz, which is attached to the right crus
of the diaphragm.
Blood Supply
Arteries
The upper half of the duodenum is supplied by the superior pancreaticoduodenal artery, which is a
branch of the gastroduodenal artery. The lower half is supplied by the inferior
pancreaticoduodenal artery, which is a branch of the superior mesenteric artery.
Veins
The superior pancreaticoduodenal vein joins the portal
vein. The inferior pancreaticoduodenal vein joins the
superior mesenteric vein.
Lymph Drainage
The lymph vessels drain upward via the pancreaticoduodenal nodes to the gastroduodenal nodes and the
celiac nodes. They drain downward via the pancreaticoduodenal nodes to the superior mesenteric
nodes.
Nerve Supply
The duodenum is supplied by the sympathetic and vagus
nerves via the celiac and the superior mesenteric plexuses.
JEJUNUM AND ILEUM
The jejunum measures approximately 8 ft. (2.5 m) long and
the ileum, approximately 12 ft. (3.6 m) long. The jejunum
begins at the duodenojejunal flexure in the upper
part of the abdominal cavity and to the left of the midline. It
is wider in diameter, thicker walled, and redder in color
than the ileum.
The coils of the ileum occupy the lower right part of the
abdominal cavity and tend to hang down into the pelvis.
The ileum ends at the ileocecal junction. The coils of the jejunum and the ileum are suspended from the
posterior abdominal wall by a fan-shaped fold of peritoneum called the
mesentery of the small intestine.
Blood Supply
Arteries
Branches of the superior mesenteric artery anastomose with one another to form arcades.
Veins
The veins drain into the superior mesenteric vein.
Lymph Drainage
The lymph passes to the superior mesenteric nodes via
intermediate mesenteric nodes.
Nerve Supply
Sympathetic and vagus nerve fibers arise from the superior
mesenteric plexus.
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