E2D Flashcards
intestines, pancreas, mesenteric arteries and portal vein
duodenum
C-shaped tube, about 10 inches long, that curves around head of pancreas; located in epigastric and umbilical regions; begins at pyloric orifice and ends at duodenojejunal flexure
its initial segment is intraperitoneal (like stomach): remaining of duodenum is secondary retroperitoneal (only its anterior surface is covered by peritoneum)
duodenum parts
1st (superior), 2nd (descending), 3rd (inferior, horizontal or transverse) and 4th (ascending)
duodenum relations
gastroduodenal artery passes posterior to 1st part of duodenum: a peptic ulcer in posterior wall of 1st part of duodenum can erode gastroduodenal artery or one of its branches causing a massive hemorrhage
gallbladder is anterior to 1st part and upper portion of 2nd part of duodenum inflammation of gallbladder can create adhesions or even a fistula between gallbladder and duodenum
superior mesenteric artery and vein pass anterior to 3rd part of duodenum; an aneurysm of SMA can compress 3rd part of duodenum causing intestinal obstruction
duodenum internal structure
in approximately the first 2cm, duodenal mucosa is smooth (duodenal ampulla/cap)
remaining of duodenum: mucosal surface has numerous folds circular folds (plicae circulares)
major duodenal papilla
small elevation located approximately half-way down posteromedial wall of 2nd part of duodenum, created by hepatopancreatic ampulla (of Vater); has small orifice at its tip (opening of hepatopancreatic ampulla) that releases bile and pancreatic enzymes into duodenum
minor duodenal papilla (inconstant)
located in 2nd part of duodenum, about 2cm above major duodenal papilla; marks opening of accessory pancreatic duct
jejunum and ileum
jejunum begins at duodenojejunal flexure and ileum ends at ileocecal junction; each has peculiar features, but there is a gradual change from one to the other (no sharp boundary between them)
coils of jejunum and ileum are intraperitoneal and freely movable; attached to posterior abdominal wall by mesentery of small intestine, which allows branches of superior mesenteric vessels, lymph vessels and nerves to reach jejunum and ileum
root of mesentery of small intestine extends inferiorly and to the right from left side of L2 to right sacroiliac joint
jejunum/ileum differences
coils of jejunum lie in upper part of infracolic compartment; coils of ileum are in lower part of infracolic compartment and pelvic cavity
jejunum has larger diameter and thicker walls than ileum
in jejunum circular folds are larger and more numerous than in ileum
jejunal arteries form less number of arcades than ileal arteries; straight arteries (vasa recta), which originate from last series of arcades, are longer in jejunum than ileum
aggregated lymphoid follicles/nodules (Peyer’s patches) are present in ileum along its antimesenteric border (not present in jejunum)
ileum has more mesenteric fat than jejunum
large intestine
extends from ileocecal junction to anus
mainly concerned with absorption of water and electrolytes and storage of undigested materials until they can be eliminated from body as feces
parts: cecum with vermiform appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal canal
ileal (ileocecal) orifice
located in medial wall of cecum; guarded by 2 mucosal folds (superior and inferior ileocecal lips, formerly known as ileocecal valve); play little or no role in preventing reflux from cecum to ileum (major role is played by circular muscle at end of ileum)
small vs large intestine
teniae coli: 3 bands of longitudinally arranged smooth muscles fibers, approximately equally spaced around circumference of large intestine named according to their relations to peritoneal attachments of transverse colon (omental tenia, mesocolic tenia and free tenia)
large intestine has fatty appendices (epiploic/omental appendices): not present in small intestine
wall of small intestine is smooth: wall of large intestine is sacculated (haustra)
vermiform appendix
narrow muscular tube containing large amount of lymphoid tissue
intraperitoneal: has small mesentery (mesoappendix) that contains appendicular vessels
McBurney’s point: located at junction of lateral and middle thirds of a line joining right ASIS to umbilicus; area of greatest tenderness in appendicitis
3 teniae coli converge at base of appendix (useful in locating appendix during surgery)
position of appendix is variable; retrocecal (most common), hanging down into pelvis against right pelvic wall, below cecum, projecting upward anterior or posterior to terminal part of ileum
sensory fibers carrying pain from appendix terminate in spinal cord at level of T10; pain referred around umbilicus
pancreas
exocrine part produces enzymes involved in digestion of proteins, fats and carbohydrates
endocrine part (pancreatic islets [of Langerhans]) produces hormones (main ones are insulin and glucagon)
elongated organ that lies in epigastric and left hypochondriac regions; deeply located on posterior abdominal wall, behind peritoneal sac (most of it is secondary retroperitoneal)
pancreas head
lies within concavity of duodenum
uncinate process: tongue-like process of lower part of head that extends to the left, posterior to superior mesenteric vessels
pancreas neck
slightly constricted part between head and body
located anterior to origins of portal vein and superior mesenteric artery
pancreas body
longest part, extends to the leg and slightly superiorly
pancreas tail
located within splenorenal ligament; comes in contact with hilum of spleen (only part of pancreas that is intraperitoneal)
pancreas anatomical relations
anteriorly: lesser sac, stomach, root of transverse mesocolon
posteriorly: common bile duct, origin of portal vein, IVC, abdominal aorta with origin of superior mesenteric artery, splenic vein, left kidney, left suprarenal gland
superiorly: splenic artery
pancreas ducts
principal (main) pancreatic duct: begins in tail and runs length of organ opens into 2nd part of duodenum (together with common bile duct) on major duodenal papilla
accessory pancreatic duct: drains upper part of head opens into 2nd part of duodenum on minor duodenal papilla
two ducts usually communicate with each other
superior mesenteric artery (SMA)
unpaired visceral branch of abdominal aorta; originates from anterior aspect of abdominal aorta at level of L1, posterior to neck of pancreas
runs inferiorly and to the right at its origin it passes anterior to left renal vein, then it passes anterior to uncinate process of pancreas and 3rd part of duodenum and continues along root of mesentery of small intestine (aneurysms of initial part of SMA can compress left renal vein or 3rd part of duodenum)
supplies lower part of head of pancreas, distal part of duodenum, jejunum, ileum, cecum, appendix, ascending colon and proximal ⅔ of transverse colon
SMA branches
inferior pancreaticoduodenal artery jejunal and ileal (intestinal) arteries ileocolic artery right colic artery middle colic
inferior pancreaticoduodenal artery
divides into anterior and posterior branches, which pass to the right supplying lower part of head of pancreas and distal half of duodenum; anastomose with superior pancreaticoduodenal branches of gastroduodenal artery (anastomosis between CT and SMA)
jejunal and ileal (intestinal) arteries
12 to 15 in number; originate from left side of SMA, run between 2 layers of mesentery of small intestine to reach coils of jejunum and ileum, form arterial arcades that increase in number from jejunum to ileum; terminal arcades give rise to straight arteries that supply intestinal wall
ileocolic artery
lowermost of branches that originate from right side of SMA, runs inferiorly and to the right, toward ileocecal junction, behind peritoneum
its branches supply terminal ileum, cecum, appendix and beginning of ascending colon
right colic artery
runs to the right, behind peritoneum, to supply ascending colon and beginning of transverse colon; exhibits considerable variability (may originate from SMA, ileocolic artery, middle colic artery or it may be absent)
middle colic
runs between 2 layers of transverse mesocolon; its branches supply proximal ⅔ of transverse colon; anastomoses with left colic artery (branch of IMA)
inferior mesenteric artery (IMA)
lowest unpaired visceral branch of abdominal aorta; originates from anterior aspect of abdominal aorta at level of L3
runs inferiorly, posterior to peritoneum, in left infracolic space, crosses left common iliac vessels and continues into pelvis as superior rectal artery
supplies distal ⅓ of transverse colon, descending colon, sigmoid colon, rectum and upper half of anal canal
inferior mesenteric artery branches
left colic artery:
sigmoid arteries
superior rectal artery
left colic artery
runs to the left, behind peritoneum, its branches supply distal ⅓ of transverse colon and descending colon, anastomoses with middle colic artery (branch of SMA)
sigmoid arteries
2 or 3 in number; run between 2 layers of sigmoid mesocolon supply sigmoid colon
superior rectal artery
inferior continuation of IMA; descends into pelvis posterior to rectum; supplies rectum and upper half of anal canal
anastomoses with middle and inferior rectal arteries (branches of internal iliac and internal pudendal arteries, respectively)
marginal artery
continuous arterial channel that skirts inner margin of colon from ileocecal junction to rectosigmoid junction
formed by anastomoses between branches of ileocolic, right colic, middle colic, left colic and sigmoid arteries
can serve as a source of collateral circulation to a part of colon after its chief arterial supply has been obstructed or ligated
portal vein
drains blood from most of alimentary canal (from lower ⅓ of esophagus to upper ½ of anal canal), spleen and pancreas; terminates in liver
begins posterior to neck of pancreas by union of superior mesenteric and splenic veins
runs superiorly and to the right, passes posterior to 1st part of duodenum, runs within hepatoduodenal ligament (posterior to proper hepatic artery and common bile duct); divides into right and left terminal branches at porta hepatis
portal vein tributaries
splenic vein inferior mesenteric vein superior mesenteric vein R/L gastric veins superior panrceaticoduodenal veins cystic veins paraumbilical veins
splenic vein
begins at hilum of spleen, runs to the right, posterior to pancreas, and inferior to splenic artery
joins superior mesenteric vein posterior to neck of pancreas to form portal vein; receives tributaries that correspond with branches of splenic artery (short gastric, left gastroepiploic, pancreatic veins) as well as inferior mesenteric vein
inferior mesenteric vein
drains territory supplied by inferior mesenteric artery (receives left colic, sigmoid and superior rectal veins); ascends on posterior abdominal wall, posterior to peritoneum; usually terminates by joining splenic vein posterior to pancreas, but may end at junction of splenic and superior mesenteric veins or drain into superior mesenteric vein
superior mesenteric vein
ascends in root of mesentery of small intestine on right side of SMA; passes anterior to 3rd part of duodenum and uncinate process of pancreas; joins splenic vein posterior to neck of pancreas to form portal vein; receives tributaries that correspond with branches of SMA (inferior pancreaticoduodenal, jejunal, ileal, ileocolic, right colic and middle colic veins) and right gastroepiploic vein
right and left gastric veins
collect blood from lesser curvature of stomach; drain directly into portal vein
superior pancreaticoduodenal veins
drain into portal vein or superior mesenteric vein
cystic veins
drain gallbladder directly into liver or join portal vein
paraumbilical veins
very small veins that run along round ligament of liver; connect veins of anterior abdominal wall with portal vein (usually its left branch)
portal-systemic anastomoses
P-SA
in normal conditions, portal venous blood passes through liver and drains into IVC, which then carries it to heart (direct route)
other routes of communication exist between portal and systemic (SVC, IVC) circulations; become important if direct route is blocked causing portal hypertension (ex.: cirrhosis of liver); in patients with portal hypertension, portal-systemic anastomoses become enlarged (varicose veins), can rupture and bleed
wherever non-peritoneal areas of intestines, liver and pancreas (portal circulation) are in contact with body wall (systemic circulation)
esophagus P-SA
in lower part of esophagus, esophageal veins that drain into left gastric vein (portal circulation) anastomose with esophageal veins that drain into azygos venous system (systemic circulation, SVC); enlargement of these veins in portal hypertension causes esophageal varices
rectum P-SA
in walls of rectum and anal canal; tributaries of superior rectal vein (portal circulation) anastomose with tributaries of middle and inferior rectal veins (systemic circulation, IVC); enlargement of these veins in portal hypertension causes internal hemorrhoids (most hemorrhoids are NOT associated with portal hypertension)
abdominal wall P-SA
in anterior abdominal wall; paraumbilical veins (portal circulation) anastomose with superficial veins of anterior abdominal wall which drain superiorly into axillary vein or inferiorly into femoral vein (systemic circulation); enlargement of these veins in portal hypertension causes caput Medusae
