Digestive System and Abdomen - Quick-Review Notes
Peritoneal Cavity
Peritoneum forms a potential space between parietal and visceral layers.
Two portions: greater sac (main) and lesser sac (omental bursa).
Lesser sac has superior recess behind the lesser omentum and inferior recess behind the stomach extending into the greater omentum.
Foramen of Winslow (epiploic foramen) connects the greater and lesser sacs.
Stomach and Omenta
Stomach has two curvatures: greater curvature and lesser curvature.
Greater omentum attaches to the greater curvature (gastrocolic ligament) and is divided into three ligaments: gastrocolic, gastrophrenic, gastrosplenic.
Lesser omentum attaches at the lesser curvature and first part of the duodenum; two parts: hepatogastric and hepatoduodenal.
Four regions of the stomach: cardia, body, fundus, pyloric region (pyloric antrum and pyloric canal).
Esophagus has left vagus (anterior) and right vagus (posterior) on abdominal part.
Angular notch (incisura angularis) marks the junction of the body with the pyloric region on the lesser curvature.
Gastric mucosa folds are rugae; pattern differs by region (fundus/body crisscross; pyloric region parallel to long axis).
Small Intestine
Upon reflection of the greater omentum, identify: duodenum, jejunum, ileum.
Duodenum: 4 parts (superior, descending, horizontal, ascending). First part is mobile; hepatoduodenal ligament attaches to it.
Inner duodenal mucosa has major and minor duodenal papillae; the hepatopancreatic ampulla (of Vater / pancreatoduodenal ampulla), formed by the union of the main pancreatic duct and the common bile duct, opens at the major papilla via hepatopancreatic sphincter (Oddi).
Accessory pancreatic duct opens at minor papilla; may join main duct or be separate.
Duodenojejunal junction (DJJ) is the mobile-jejunum junction; supported by suspensory ligament of Treitz, which supports the duodenojejunal flexure and part of the duodenum.
Jejunum vs ileum: jejunum is thicker-walled; ileum thinner; jejunum forms most of proximal 2/5 of mobile small intestine.
Ileum ends at the ileocecal junction; root of the mesentery runs obliquely from the duodenojejunal junction to the ileocecal junction.
Large Intestine
Large intestine frames the small intestine: cecum and ascending on the right; transverse on top; descending and sigmoid on left.
Cecum: contains iliocecal valve (ventral/anterior lip) and orifice; appendix opens into the cecum below the ileocecal orifice; appendix position varies; teniae coli converge at the base.
Appendix positions: retrocecal most common; others include paracecal, subcecal, pelvically, etc.
Taeniae coli, haustra, and appendices epiploicae are characteristic features of the colon; rectum lacks haustra and appendices.
Transverse colon has a freely movable segment; mesentery is the transverse mesocolon and is related to the inferior border of the pancreas.
Rectosigmoid junction around the level of S-3.
Liver, Gallbladder, and Biliary System
Liver surfaces: diaphragmatic and visceral; visceral surface contains IVC, gallbladder, ligamentum venosum, ligamentum teres, and porta hepatis.
Porta hepatis (hilus) transmits portal triad vessels: portal veins (right/left branches), hepatic arteries (right/left), and bile ducts (right/left).
Lesser omentum extends from the lesser curvature and initial duodenum to the visceral surface of the liver; right margin contains the hepatoduodenal ligament forming the portal triad boundary, which encloses the common bile duct (lateral), hepatic artery proper (medial), and portal vein (posterior).
Bare area of liver is the region without peritoneal covering; coronary and triangular ligaments anchor the liver to the diaphragm.
Falciform ligament suspends the liver; left triangular and right triangular ligaments connect liver to diaphragm.
Gallbladder: located on visceral surface of liver; fundus, body, neck; neck forms the cystic duct joining the common hepatic duct to form the common bile duct.
Cystic artery typically in Calot’s triangle (cystic duct, common hepatic duct, liver).
Common bile duct formed by union of hepatic duct(s) and cystic duct; opens into the major duodenal papilla.
Clinical notes: cholecystoenteric fistula can cause bile/gallstone passage to GI tract; gallstones can lodge at the hepatopancreatic ampulla.
Epiploic foramen (Winslow) connects greater and lesser sacs; hepatoduodenal ligament forms anterior wall; portal triad structures lie within the ligament.
Pancreas and Spleen
Pancreas regions: head (within duodenal curve), uncinate process, neck, body, tail (contacts splenic hilum).
Head lies near IVC; uncinate process lies posterior to superior mesenteric vessels; SMA crosses the head.
Pancreaticoduodenal arteries: anterior/posterior branches from the superior pancreaticoduodenal; inferior pancreaticoduodenal usually from SMA.
Pancreatic ducts: main pancreatic duct runs from tail to head, joins the common bile duct to form the hepatopancreatic ampulla.
Spleen: located in left upper quadrant, posterior to stomach; hilus, visceral surface, diaphragmatic surface.
Peritoneal attachments: splenorenal (lienorenal) ligament and gastrosplenic ligament.
Blood Vessels (Abdomen)
Abdominal aorta: begins at and ends at bifurcating into common iliac arteries.
Celiac trunk (unpaired) → three branches: common hepatic, left gastric, splenic.
Common hepatic artery branches: hepatic artery proper; gastroduodenal artery.
Hepatic artery proper branches: right gastric, left hepatic, right hepatic (often gives cystic artery).
Gastroduodenal branches: supraduodenal (absent 30%), superior pancreaticoduodenal, right gastroepiploic.
Splenic artery branches: short gastric arteries; left gastroepiploic.
Superior mesenteric artery (SMA): branches include inferior pancreaticoduodenal, intestinal branches with vasa recta, ileocolic (gives appendicular artery), right colic, middle colic. Lies posterior to neck of pancreas; anterior to left renal vein and to 3rd part of duodenum.
Inferior mesenteric artery (IMA): left colic, sigmoidal arteries, superior rectal.
Renal arteries: posterior to renal veins; right renal artery longer than left.
Gonadal (testicular/ovarian) arteries: arise from aorta below renal arteries.
Portal circulation: portal vein formed by superior mesenteric and splenic veins; inferior mesenteric vein may join either the SMV, splenic vein, or their junction.
Draining veins: SMV, splenic vein, IMV; hepatic veins drain to IVC; GI tract blood does not drain directly into IVC.
Marginal artery (Drummond) runs along inner border of the large intestine via anastomoses of SMV and IMV branches.
Portal Hypertension and Collaterals
Portal hypertension causes dilation of submucosal veins in lower esophagus (esophageal varices), rectum, and around the umbilicus (caput medusae).
Paraumbilical veins connect with the periumbilical venous system; left gastric and esophageal plexuses communicate with azygos system.
Kidneys, Suprarenal Glands, and Ureters
Kidneys: retroperitoneal; right kidney usually lower than left due to liver.
Renal hilus: renal vein anterior, ureter posterior, renal artery between.
Renal fascia divides perirenal fat (inside) and pararenal fat (outside).
Left renal vein is longer; it crosses between the aorta and SMA and receives tributaries from left testicular/ovarian veins.
The renal pelvis branches into major calyces, which in turn branch into minor calyces, collecting urine from the renal papillae.
Ureters descend retroperitoneally to join the bladder later; renal pelvis is at the hilus.
Suprarenal (adrenal) glands: right (triangular) sits posterior to IVC; left (semilunar) adjacent to left kidney.
Arterial supply to adrenal glands from multiple sources: superior (from inferior phrenic), middle (from aorta), inferior (from renal); venous drainage typically right directly into IVC and left into the left renal vein.
Diaphragm and Posterior Abdominal Wall
Diaphragm portions: sternal, costal, lumbar, central tendon.
Lumbar portion formed by two crura: left crus and right crus; esophageal hiatus formed by the right crus; Treitz ligament extends from the right crus to support the duodenojejunal flexure.
Arcuate ligaments (lumbocostal arches): medial (over psoas), lateral (over quadratus lumborum), and median (anterior to aorta).
Major openings in the diaphragm with vertebral levels: caval foramen at ; esophageal hiatus at ; aortic hiatus at .
Spermatic Cord, Scrotum, and Testis
Spermatic cord contents: vas deferens, testicular artery, pampiniform plexus, cremasteric artery, artery to vas, genital branch of genitofemoral nerve, autonomic fibers, lymphatics.
The spermatic cord passes through the deep inguinal ring, which is located superior and lateral to the inferior epigastric vessels, before descending into the scrotum.
Coverings of the spermatic cord (from exterior to interior): external spermatic fascia (from external oblique aponeurosis), cremasteric fascia/muscle (from internal oblique), internal spermatic fascia (from transversalis fascia).
Processus vaginalis and tunica vaginalis; gubernaculum testis leaves a scrotal ligament postnatally.
Testis: tunica vaginalis (visceral and parietal layers); tunica albuginea; septa dividing the testis into lobules.
Nerves of the Abdomen (Overview)
Subcostal nerve = intercostal nerve #12 (T12).
Lumbar plexus branches near psoas major:
Lateral border: iliohypogastric, ilioinguinal, lateral femoral cutaneous, femoral.
Genitofemoral emerges on psoas and splits into genital (cremasteric reflex motor) and femoral (sensory thigh) branches.
Obturator and accessory obturator nerves (the latter absent in many).
Lumbosacral trunk contributes to sacral plexus.
Quick Reference: Key Spatial Relationships and Landmarks
Portal triad in hepatoduodenal ligament: portal vein (posterior), proper hepatic artery (medial), common bile duct (lateral).
Bare area and coronary ligaments anchor liver to diaphragm; triangular ligaments anchor lobes.
The gastrocolic ligament covers the transverse colon; gastrophrenic to the diaphragm; gastrosplenic to the spleen.
The left gastric vein drains lower esophagus into portal system; esophageal varices arise from portal hypertension.
The marginal artery provides an anastomotic channel along the colon between SMV and IMV branches.
Clinical Correlations (Condensed)
Cholecystoenteric fistula: inflamed gallbladder adheres to GI tract, gallstone can pass through GI tract causing obstruction.
Portal hypertension: esophageal varices, rectal varices, caput medusae.
Superior Mesenteric Syndrome (Nutcracker): left renal vein and third part of the duodenum pass between the aorta and SMA and may be compressed.
Consider variability in appendix position when diagnosing appendicitis (McBurney point localization).
Peritoneal Cavity
Peritoneum forms a potential space between parietal and visceral layers.
Two portions: greater sac (main) and lesser sac (omental bursa).
Lesser sac has superior recess behind the lesser omentum and inferior recess behind the stomach extending into the greater omentum.
Foramen of Winslow (epiploic foramen) connects the greater and lesser sacs.
Stomach and Omenta
Stomach has two curvatures: greater curvature and lesser curvature.
Greater omentum attaches to the greater curvature (gastrocolic ligament) and is divided into three ligaments: gastrocolic, gastrophrenic, gastrosplenic.
Lesser omentum attaches at the lesser curvature and first part of the duodenum; two parts: hepatogastric and hepatoduodenal.
Four regions of the stomach: cardia, body, fundus, pyloric region (pyloric antrum and pyloric canal).
Esophagus has left vagus (anterior) and right vagus (posterior) on abdominal part.
Angular notch (incisura angularis) marks the junction of the body with the pyloric region on the lesser curvature.
Gastric mucosa folds are rugae; pattern differs by region (fundus/body crisscross; pyloric region parallel to long axis).
Small Intestine
Upon reflection of the greater omentum, identify: duodenum, jejunum, ileum.
Duodenum: 4 parts (superior, descending, horizontal, ascending). First part is mobile; hepatoduodenal ligament attaches to it.
Inner duodenal mucosa has major and minor duodenal papillae; the hepatopancreatic ampulla (of Vater / pancreatoduodenal ampulla), formed by the union of the main pancreatic duct and the common bile duct, opens at the major papilla via hepatopancreatic sphincter (Oddi).
Accessory pancreatic duct opens at minor papilla; may join main duct or be separate.
Duodenojejunal junction (DJJ) is the mobile-jejunum junction; supported by suspensory ligament of Treitz, which supports the duodenojejunal flexure and part of the duodenum.
Jejunum vs ileum: jejunum is thicker-walled; ileum thinner; jejunum forms most of proximal 2/5 of mobile small intestine.
Ileum ends at the ileocecal junction; root of the mesentery runs obliquely from the duodenojejunal junction to the ileocecal junction.
Large Intestine
Large intestine frames the small intestine: cecum and ascending on the right; transverse on top; descending and sigmoid on left.
Cecum: contains iliocecal valve (ventral/anterior lip) and orifice; appendix opens into the cecum below the ileocecal orifice; appendix position varies; teniae coli converge at the base.
Appendix positions: retrocecal most common; others include paracecal, subcecal, pelvically, etc.
Taeniae coli, haustra, and appendices epiploicae are characteristic features of the colon; rectum lacks haustra and appendices.
Transverse colon has a freely movable segment; mesentery is the transverse mesocolon and is related to the inferior border of the pancreas.
Rectosigmoid junction around the level of S-3.
Liver, Gallbladder, and Biliary System
Liver surfaces: diaphragmatic and visceral; visceral surface contains IVC, gallbladder, ligamentum venosum, ligamentum teres, and porta hepatis.
Porta hepatis (hilus) transmits portal triad vessels: portal veins (right/left branches), hepatic arteries (right/left), and bile ducts (right/left).
Lesser omentum extends from the lesser curvature and initial duodenum to the visceral surface of the liver; right margin contains the hepatoduodenal ligament forming the portal triad boundary, which encloses the common bile duct (lateral), hepatic artery proper (medial), and portal vein (posterior).
Bare area of liver is the region without peritoneal covering; coronary and triangular ligaments anchor the liver to the diaphragm.
Falciform ligament suspends the liver; left triangular and right triangular ligaments connect liver to diaphragm.
Gallbladder: located on visceral surface of liver; fundus, body, neck; neck forms the cystic duct joining the common hepatic duct to form the common bile duct.
Cystic artery typically in Calot’s triangle (cystic duct, common hepatic duct, liver).
Common bile duct formed by union of hepatic duct(s) and cystic duct; opens into the major duodenal papilla.
Clinical notes: cholecystoenteric fistula can cause bile/gallstone passage to GI tract; gallstones can lodge at the hepatopancreatic ampulla.
Epiploic foramen (Winslow) connects greater and lesser sacs; hepatoduodenal ligament forms anterior wall; portal triad structures lie within the ligament.
Pancreas and Spleen
Pancreas regions: head (within duodenal curve), uncinate process, neck, body, tail (contacts splenic hilum).
Head lies near IVC; uncinate process lies posterior to superior mesenteric vessels; SMA crosses the head.
Pancreaticoduodenal arteries: anterior/posterior branches from the superior pancreaticoduodenal; inferior pancreaticoduodenal usually from SMA.
Pancreatic ducts: main pancreatic duct runs from tail to head, joins the common bile duct to form the hepatopancreatic ampulla.
Spleen: located in left upper quadrant, posterior to stomach; hilus, visceral surface, diaphragmatic surface.
Peritoneal attachments: splenorenal (lienorenal) ligament and gastrosplenic ligament.
Blood Vessels (Abdomen)
Abdominal aorta: begins at and ends at bifurcating into common iliac arteries.
Celiac trunk (unpaired)
three branches: common hepatic, left gastric, splenic.
Common hepatic artery branches: hepatic artery proper; gastroduodenal artery.
Hepatic artery proper branches: right gastric, left hepatic, right hepatic (often gives cystic artery).
Gastroduodenal branches: supraduodenal (absent 30%), superior pancreaticoduodenal, right gastroepiploic.
Splenic artery branches: short gastric arteries; left gastroepiploic.
Superior mesenteric artery (SMA): branches include inferior pancreaticoduodenal, intestinal branches with vasa recta, ileocolic (gives appendicular artery), right colic, middle colic. Lies posterior to neck of pancreas; anterior to left renal vein and to 3rd part of duodenum.
Inferior mesenteric artery (IMA): left colic, sigmoidal arteries, superior rectal.
Renal arteries: posterior to renal veins; right renal artery longer than left.
Gonadal (testicular/ovarian) arteries: arise from aorta below renal arteries, typically at the level of the second and third lumbar vertebrae ().
Portal circulation: portal vein formed by superior mesenteric and splenic veins; inferior mesenteric vein may join either the SMV, splenic vein, or their junction.
Draining veins: SMV, splenic vein, IMV; hepatic veins drain to IVC; GI tract blood does not drain directly into IVC.
Marginal artery (Drummond) runs along inner border of the large intestine via anastomoses of SMV and IMV branches.
Portal Hypertension and Collaterals
Portal hypertension causes dilation of submucosal veins in lower esophagus (esophageal varices), rectum, and around the umbilicus (caput medusae).
Paraumbilical veins connect with the periumbilical venous system; left gastric and esophageal plexuses communicate with azygos system.
Kidneys, Suprarenal Glands, and Ureters
Kidneys: retroperitoneal; right kidney usually lower than left due to liver.
Renal hilus: renal vein anterior, ureter posterior, renal artery between.
Renal fascia divides perirenal fat (inside) and pararenal fat (outside).
Left renal vein is longer; it crosses between the aorta and SMA and receives tributaries from left testicular/ovarian veins.
The renal pelvis branches into major calyces, which in turn branch into minor calyces, collecting urine from the renal papillae.
Ureters descend retroperitoneally to join the bladder later; renal pelvis is at the hilus.
Suprarenal (adrenal) glands: right (triangular) sits posterior to IVC; left (semilunar) adjacent to left kidney.
Arterial supply to adrenal glands from multiple sources: superior (from inferior phrenic), middle (from aorta), inferior (from renal); venous drainage typically right directly into IVC and left into the left renal vein.
Diaphragm and Posterior Abdominal Wall
Diaphragm portions: sternal, costal, lumbar, central tendon.
Lumbar portion formed by two crura: left crus and right crus; esophageal hiatus formed by the right crus; Treitz ligament extends from the right crus to support the duodenojejunal flexure.
Arcuate ligaments (lumbocostal arches): medial (over psoas), lateral (over quadratus lumborum), and median (anterior to aorta).
Major openings in the diaphragm with vertebral levels: caval foramen at ; esophageal hiatus at ; aortic hiatus at .
Spermatic Cord, Scrotum, and Testis
Spermatic cord contents: vas deferens, testicular artery, pampiniform plexus, cremasteric artery, artery to vas, genital branch of genitofemoral nerve, autonomic fibers, lymphatics.
The spermatic cord passes through the deep inguinal ring, which is located superior and lateral to the inferior epigastric vessels, before descending into the scrotum.
Coverings of the spermatic cord (from exterior to interior): external spermatic fascia (from external oblique aponeurosis), cremasteric fascia/muscle (from internal oblique), internal spermatic fascia (from transversalis fascia).
Processus vaginalis and tunica vaginalis; gubernaculum testis leaves a scrotal ligament postnatally.
Testis: tunica vaginalis (visceral and parietal layers); tunica albuginea; septa dividing the testis into lobules.
Nerves of the Abdomen (Overview)
Subcostal nerve = intercostal nerve #12 (T12).
Lumbar plexus branches near psoas major:
Lateral border: iliohypogastric, ilioinguinal, lateral femoral cutaneous, femoral.
Genitofemoral emerges on psoas and splits into genital (cremasteric reflex motor) and femoral (sensory thigh) branches.
Obturator and accessory obturator nerves (the latter absent in many).
Lumbosacral trunk contributes to sacral plexus.
Quick Reference: Key Spatial Relationships and Landmarks
Portal triad in hepatoduodenal ligament: portal vein (posterior), proper hepatic artery (medial), common bile duct (lateral).
Bare area and coronary ligaments anchor liver to diaphragm; triangular ligaments anchor lobes.
The gastrocolic ligament covers the transverse colon; gastrophrenic to the diaphragm; gastrosplenic to the spleen.
The left gastric vein drains lower esophagus into portal system; esophageal varices arise from portal hypertension.
The marginal artery provides an anastomotic channel along the colon between SMV and IMV branches.
Clinical Correlations (Condensed)
Cholecystoenteric fistula: inflamed gallbladder adheres to GI tract, gallstone can pass through GI tract causing obstruction.
Portal hypertension: esophageal varices, rectal varices, caput medusae.
Superior Mesenteric Syndrome (Nutcracker): left renal vein and third part of the duodenum pass between the aorta and SMA and may be compressed.
Consider variability in appendix position when diagnosing appendicitis (McBurney point localization).