Diagnostic Ultrasound - Abdomen and Pelvis

Bowel
Anatomy: Abdomen
GROSS ANATOMY
Divisions
• Esophagus: Cervical and thoracic segments
• Stomach
○ Hollow muscular organ between esophagus and small
intestine
○ Location: Intraperitoneal, in left upper quadrant,
bordered superiorly by left hemidiaphragm,
posterolaterally by spleen, posteroinferiorly by pancreas
– Greater omentum attached from greater curvature
and drapes over small and large intestines
– Lesser omentum attached from lesser curvature to
porta hepatis, covers lesser sac
○ Function
– Gastric acid production for breakdown of large
molecules of food into smaller molecules in
preparation for small intestinal absorption
– Storage of food
○ Sections
– Gastroesophageal junction/cardia, lower esophageal
sphincter
– Fundus and body: Delineated by horizontal plane
passing through cardia
– Antrum/pylorus: Lower section facilitating entry of
gastric contents into duodenum
○ Curvatures
– Greater curvature: Lateral wall of stomach
– Lesser curvature: Medial wall of stomach
○ Rugae/internal ridges increase surface area for digestion
○ Arterial supply
– Right and left gastric arteries supply lesser curvature
– Right and left gastroepiploic arteries supply greater
curvature
– Short gastric artery supplies fundus
○ Venous drainage
– Follow arteries and drain into portal vein and its
tributaries
• Small bowel
○ Between stomach and large intestine
○ ~ 4-7 meters in length
○ Centrally located in abdomen
○ Intraperitoneal, except for 2nd-4th portions of
duodenum
○ Function: Further breakdown of food molecules from
stomach with eventual absorption
○ Intraluminal extensions/folds valvulae conniventes
increase surface area for absorption
– Abundant in proximal small bowel, decrease in
number in distal small bowel loops
○ Duodenum
– C-shaped hollow tube connecting stomach with
jejunum
– Begins with duodenal bulb, ends in ligament of Treitz
(duodenojejunal junction)
– Arterial supply and venous drainage: Superior and
inferior pancreaticoduodenal artery,
pancreaticoduodenal veins
○ Jejunum
– Connects duodenum with ileum
– ~ 2.5 meters in length
– Begins at ligament of Treitz
– Along with ileum, suspended by mesentery
– Arterial supply and venous drainage: Superior
mesenteric artery and vein
○ Ileum
– Connects jejunum with ascending colon
– ~ 3.5 meters in length
– Along with jejunum, suspended by mesentery
– Arterial supply and venous drainage: Superior
mesenteric artery and vein
• Large bowel
○ Between small bowel and anus
○ ~ 1.5 meters in length
○ Peripherally located in abdomen
– Cecum and appendix, transverse colon, and
rectosigmoid are intraperitoneal
– Ascending colon, descending colon, and middle
rectum are retroperitoneal
– Distal rectum is extraperitoneal
○ Function: Absorption of remaining water, storage, and
elimination of waste
○ Sections
– Ascending colon: Located in right side of abdomen,
includes cecum where appendix arises
– Hepatic flexure: Turn of colon at liver
– Transverse colon: Traverses upper abdomen
– Splenic flexure: Turn of colon at spleen
– Descending colon: Left side of abdomen
– Sigmoid/rectum: At posterior pelvis
○ With taenia coli: 3 bands of smooth muscle just under
serosa
– Haustration: Sacculations in colon resulting from
contraction of taenia coli
– Epiploic appendages: Small fat accumulations on
viscera
○ Arterial supply
– Superior mesenteric artery supplies colon from
appendix through splenic flexure
– Ileocolic branch supplies cecum
– Right colic branch supplies ascending colon
– Middle colic branch supplies transverse colon
– Inferior mesenteric artery supplies descending colon
through rectum
– Left colic branch supplies descending colon
– Sigmoid branches supply sigmoid
– Superior rectal artery supplies superior rectum
– Middle and inferior rectum are supplied by arteries of
same name originating from internal iliac artery
○ Venous drainage
– Superior and inferior mesenteric veins
• Anus
○ External opening of rectum
– Termination of gastrointestinal tract
○ With sphincters for controlling defecation
○ Internal anal sphincter
– Thin ring of smooth muscle surrounding anal canal,
deep to submucosa
– Under involuntary control
– Continuous with muscularis propria of rectum
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