Supplies gut as far as opening of CBD, + foregut derivatives (liver, spleen & pancreas). Arises at T12, between crura of diaphragm a little below the median arcuate ligament.
- flanked by preaortic lymph nodes, with coeliac canglia on each side (sent along its branches)
- branches at upper border of pancreas (see Pl 284), into:
Runs across L crus, raises pancreatogastric fold, gives off oesophageal branch, enters lesser omentum and turns to R to run along lesser curve of stomach.
Passes to L along upper border of pancreas (giving off numerous pancreatic branches), turns forward in lienorenal ligament to hilum of spleen giving off ~6 short gastric vessels.
- ends as L gastroepiploic artery, continues along gr curve.
- may also give a short posterior gastric artery mid-way along its course.
Passes down & to R over pancreas as far as D1; then passes forward (raising peritoneal fold called the right gastropancreatic fold) at and curves up epiploic foramen as hepatic artery (lies on L of bile duct)
- this divides into R and L branches at the porta hepatis
- R gastric artery given off as it turns up into epiploic foramen (see Pl282) Ð runs along lesser curvature to meet L gastric.
- after giving off gastroduodenal artery.
- Gastroduodenal artery given off earlier, passes down behind the duodenum (vulnerable in active PUD) and divides into:
o i) R gastroepiploic (Pl283): passes forward between D1 and pancreas to reach greater curvature between two layers of greater omentum, Runs close to stomach; anastomoses with the other gastroepiploic
o ii) superior pancreaticoduodenal arteries (divides into small anterior and large posterior branches) which anastomose with similar branches from the inferior artery off the SMA. Supply duodenum, head of pancreas and bile duct.
The entrance of the bile duct marks the foregut / midgut boundary.
Veins correspond with arteries (R and L gastric, R and L gastroepiploic) ˆ portal vein
Portal vein formed by splenic and SMV behind neck of pancreas.
- veins of stomach drain into nearest part of SMV/portal vein complex.
- lower 1/3 of oesophagus drains into L gastric vein.
L gastric leaves lesser curvature by oesophagus, passes behind peritoneum of lesser sac to portal vein.
R gastric runs along lesser curvature to pylorus, and empties into the portal vein.
There is no gastroduodenal vein (closest equivalent is the prepyloric vein, runs over front of pylorus).
Short gastric and L gastroepiploic veins drain stomach through greater omentum and gastrosplenic ligament into hilum of spleen (ˆ empty to splenic vein)
Splenic vein: lies on (1) hilum of L kidney, (2) L psoas, (3) L sympathetic trunk, (4)L crus, (5) aorta & (6) IVC. Lies in front of L renal vein along its upper border (¨ Warren shunt). Below splenic artery.
- receives many tributaries from the tail, body, neck and head of the pancreas along the way
R gastroepiploic vein runs to right in greater omentum , descends over pancreas, collects anterior superior gastroepiploic vein and a tributary from the transverse colon and empties into the SMV.
Arises from L1 level, 1cm below coeliac. Forms axis of rotation of midgut loop; branches to proximal midgut arise from L, to caudal midgut from R. Descends behind splenic vein and pancreas with SMV lying to R, runs over L renal vein, uncinate process of pancreas and D3 before entering mesentery.
- hence can cause varicocoele through pressure on L renal vein, or chronic duodenal ileus
Runs between duodenum & pancreatic head (supplies both), splits ant and post & anastomoses with its superior colleague. R hepatic artery may arise with it and run up behind pancreas & portal vein.
Run between mesentery layers. Form arcades ¨ straight end arteries to intestine with ÒwindowsÓ between. Jejunal windows tall & narrow, ileal ones short & broad.
From R side of SMA;
branches are ileal (anastomosing with terminal SMA) and colic (anastomosing with R colic).
Terminal anterior & posterior branches (of ileal branch) supply caecum; appendiceal
artery supplies appendix from posterior
branch.
From R of SMA (or from middle colic or ileocolic or is absent).
- crosses right psoas, gonadal vessels, ureter and genitofemoral nerve (ant to everything)
- desc and ascending branches anastomose around mesenteric border as usual.
Highest branch from R side of SMA; runs forward in transverse mesocolon where an avascular window lies to R of it (used to access lesser sac or posterior stomach wall).
- arises at lower border of neck of pancreas and ascends between layers of transverse mesocolon
All branches of SMA have corresponding vein which joins SMV lying to R of SMA. SMV crosses the D3 and uncinate process of pancreas, then runs behind D1 as portal vein.
- Middle colic vein is guide to SMV at operation.
From aorta at level of L3 (umbilicus), 3-4cm above bifurcation. Runs obliquely down to pelvic brim immediately beneath peritoneal floor, and enters pelvis at bifurcation of L common iliac vessels and continues as superior rectal artery in the sigmoid mesocolon root.
- DoesnÕt cross the ureter but all its branches do (anteriorly).
- Supplies mucous membrane as far as upper third of anal canal, ie dentate line (muscle of rectal ampulla receives reinforcement from middle & inferior rectal arteries)
-
Desc branch
heads to LIF and gives braches that continue the inner colonic marginÕs
anastomotic channel.
3-4 branches to sigmoid colon, form anastomosing loops, last with the superior rectal artery.
Superior rectal vein (to L of superior rectal artery) ¨ IMV at pelvic brim which runs up to L of IMA.
- tributaries have same names as arteries
- lies on psoas, gonadal vessels, ureter and genitofemoral nerve.
- higher up lies to L of D-J flexure (see 292) before passing to R raising a peritoneal ridge with paraduodenal recess below it. IMV then passes below body of pancreas, anterior to L renal vein, and joins splenic or superior mesenteric vein (by running along inferior to splenic)
i)
Lymphoid follicles throughout mucous membrane of GIT;
aggregated into PeyerÕs patches in
terminal ileum. These enter a chain
of nodes common to small and large intestines:
ii) Mural nodes: in mesentery or small intestine; and paracolic nodes in colon
iii) Intermediate nodes lie along main blood vessels of supply
iv) Preaortic nodes.
Sympathetic & parasympathetic nerves supply entire GIT; running with arteries.
Most are via coeliac plexus; inferior hypogastric plexus contributes to hindgut.
2 plexuses are concentrations of nerve cells and fibres to the GI tract: collectively the enteric n.s.
i) Myenteric plexus (of Auerbach) lie between muscle layers
ii) Submucous plexuses (of Meissner)in submucosa.
Sympathetics (postganglionic, inhibitory) supply from spinal cord; parasympathetic (preganglionic, excitatory) from vagus & inferior hypogastric plexus.
- these fibres never pass directly to gut wall, as enteric plexi always intervene; the gut wall can function without the inputs
Afferents (some cells in the ganglion) pass via both sympathetics and parasympathetics (including pain)