VISCERAL BRANCHES OF THE ABDOMINAL AORTA

Detailed Anatomy Notes for Medical Students

OVERVIEW OF THE ABDOMINAL AORTA

Classification of Branches

PART I — UNPAIRED VISCERAL BRANCHES

1. CELIAC TRUNK (Celiac Axis / Truncus Coeliacus)

Origin & Level

• Arises from the anterior surface of the abdominal aorta immediately below the aortic hiatus
• Level: T12–L1 (anterior to upper part of vertebra LI)
• Supplies the foregut (abdominal esophagus → superior duodenum/proximal descending duodenum)

Primary Branches — "The Tripod of Haller"

        CELIAC TRUNK (T12-L1)
              |
    __________|__________
    |          |          |
Left       Splenic    Common
Gastric    Artery     Hepatic
Artery               Artery

Gray's Anatomy for Students — Fig. 4.124: Celiac Trunk distribution and DSA

A. Left Gastric Artery

• Smallest branch of the celiac trunk
• Course:
  • Ascends to the cardioesophageal junction
  • Gives esophageal branches upward (some pass through the esophageal hiatus to anastomose with thoracic aortic esophageal branches)
  • Turns right and descends along the lesser curvature of the stomach in the lesser omentum
• Supplies: Both surfaces of the stomach along the lesser curvature
• Anastomoses with the right gastric artery (from hepatic artery proper)

B. Splenic Artery

• Largest branch of the celiac trunk
• Course: Takes a tortuous course to the left along the superior border of the pancreas → travels in the splenorenal ligament → divides into multiple branches entering the hilum of the spleen
• Branches given off along its course:
  1. Pancreatic branches — numerous small branches to neck, body, and tail of pancreas
  2. Short gastric arteries — pass through the gastrosplenic ligament to supply the fundus of the stomach
  3. Left gastro-omental artery — runs rightward along the greater curvature of the stomach, anastomosing with the right gastro-omental artery

C. Common Hepatic Artery

• Medium-sized branch; the only celiac branch that passes to the right
• Divides into two terminal branches:

i. Hepatic Artery Proper

• Ascends to the liver in the free edge of the lesser omentum
• Runs left of the bile duct and anterior to the portal vein
• Divides near the porta hepatis into:
  • Right hepatic artery — gives off the cystic artery to the gallbladder
  • Left hepatic artery
• Also gives off: Right gastric artery — runs left along the lesser curvature, anastomosing with the left gastric artery

ii. Gastroduodenal Artery

• Descends posterior to the 1st part of duodenum
• Branches into:
  • Right gastro-omental artery — runs leftward along the greater curvature of the stomach, anastomosing with the left gastro-omental artery
  • Superior pancreaticoduodenal artery — divides into anterior and posterior branches that descend on each side of the head of the pancreas to anastomose with the inferior pancreaticoduodenal branches of the SMA

Key Point: The stomach receives supply from ALL THREE celiac trunk branches — it is the only organ with this distinction.

2. SUPERIOR MESENTERIC ARTERY (SMA)

Origin & Level

• Arises from the anterior surface of the abdominal aorta immediately below the celiac trunk
• Level: Lower part of vertebra LI (posterior to neck of pancreas)
• Supplies the midgut (distal duodenum → proximal 2/3 of transverse colon)

Relations

• Anterior: Splenic vein, neck of the pancreas
• Posterior: Left renal vein, uncinate process of pancreas, inferior part of duodenum

Gray's Anatomy for Students — Fig. 4.127: Initial branching and relationships of the SMA

Branches

        SUPERIOR MESENTERIC ARTERY (L1)
                     |
    _________________|_________________
    |          |                   |
LEFT SIDE    RIGHT SIDE (3)     FIRST BRANCH
(Multiple)                        |
    |                        Inferior Pancreati-
Jejunal &                    coduodenal Artery
Ileal arteries
              |          |          |
           Middle      Right     Ileocolic
           Colic       Colic     Artery
           Artery      Artery

A. Inferior Pancreaticoduodenal Artery

• First branch of the SMA
• Immediately divides into anterior and posterior branches
• These ascend on either side of the head of the pancreas
• Anastomose superiorly with the anterior and posterior superior pancreaticoduodenal arteries (from gastroduodenal)
• Supplies: Head and uncinate process of pancreas, duodenum

B. Jejunal and Ileal Arteries (Left-side branches)

• Numerous branches arising from the left side of the SMA main trunk
• Pass between two layers of the mesentery
• Form anastomosing arches (arcades) — number increases progressively from jejunum to ileum:
  • Jejunum: 1–2 arcades, then long vasa recta, narrow windows in the mesentery
  • Ileum: Multiple (up to 4–5) arcades, then short vasa recta, wide/broad windows in mesentery
• Vasa recta = straight end-arteries providing direct supply to gut wall

Gray's Anatomy for Students — Fig. 4.128: SMA distribution

C. Middle Colic Artery (Right-side, 1st)

• Arises as SMA emerges from beneath the pancreas
• Enters the transverse mesocolon, divides into:
  • Right branch → anastomoses with right colic artery
  • Left branch → anastomoses with left colic artery (IMA branch)
• Supplies: Transverse colon (proximal 2/3)

D. Right Colic Artery (Right-side, 2nd)

• Inconsistent branch (may be absent or arise from ileocolic)
• Passes retroperitoneally to the right → supplies ascending colon
• Divides into:
  • Descending branch → anastomoses with ileocolic artery
  • Ascending branch → anastomoses with middle colic artery

E. Ileocolic Artery (Right-side, 3rd / terminal)

• Final right-side branch
• Descends toward the right iliac fossa
• Divides into superior and inferior branches:
  • Superior branch → ascending colon (anastomoses with right colic artery)
  • Inferior branch → divides further into:
    • Colic branch — supplies first part of ascending colon
    • Anterior cecal branch — anterior cecum
    • Posterior cecal branch — posterior cecum
    • Appendicular artery — runs in free margin of mesoappendix to supply the appendix
    • Ileal branch — supplies terminal ileum; anastomoses with SMA

3. INFERIOR MESENTERIC ARTERY (IMA)

Origin & Level

• Smallest of the three anterior branches of the abdominal aorta
• Arises from the anterior surface of the abdominal aorta at vertebra LIII
• Initially descends anterior to the aorta, then passes to the left
• Supplies the hindgut (distal 1/3 transverse colon → upper rectum)

Branches

        INFERIOR MESENTERIC ARTERY (L3)
                     |
       ______________|______________
       |                           |
   Left Colic              Sigmoid Arteries
   Artery                  (2-4 branches)
       |                           |
   Ascending                Terminal Branch:
   Branch  +                Superior Rectal
   Descending                   Artery
   Branch

Gray's Anatomy for Students — Fig. 4.129: IMA distribution

A. Left Colic Artery

• First branch of the IMA; ascends retroperitoneally
• Divides into:
  • Ascending branch → passes anterior to left kidney → enters transverse mesocolon → supplies upper descending colon and distal transverse colon; anastomoses with the middle colic artery (SMA)
  • Descending branch → supplies lower descending colon; anastomoses with first sigmoid artery

B. Sigmoid Arteries

• 2–4 branches descending to the left in the sigmoid mesocolon
• Supply: Lowest descending colon and sigmoid colon
• Anastomose superiorly with left colic branches, inferiorly with superior rectal artery

C. Superior Rectal Artery

• Terminal branch of the IMA
• Descends into the pelvic cavity in the sigmoid mesocolon, crossing left common iliac vessels
• At vertebra SIII it divides into two terminal branches descending on each side of the rectum
• Anastomoses with:
  • Middle rectal arteries (from internal iliac artery)
  • Inferior rectal arteries (from internal pudendal artery)

PART II — PAIRED VISCERAL BRANCHES

1. Middle Suprarenal Arteries

• Small, lateral branches of the abdominal aorta arising just above the renal arteries
• Part of the triple blood supply to the suprarenal gland (alongside superior suprarenal from inferior phrenic, and inferior suprarenal from renal artery)

2. Renal Arteries

• Lateral branches, largest paired visceral branches
• Arise just inferior to the SMA origin, between vertebrae LI–LII
• Right renal artery is longer (passes behind the IVC, right renal vein, head of pancreas, and descending duodenum)
• Left renal artery is shorter (passes behind the left renal vein, body of pancreas, and splenic vein)
• Each divides into segmental arteries (end-arteries) supplying kidney segments
• Also give off inferior suprarenal arteries

3. Testicular / Ovarian Arteries

• Anterior branches arising below the renal arteries
• Long, slender vessels passing downward and laterally on the anterior surface of psoas major
• Testicular arteries → pass through inguinal canal to supply testes
• Ovarian arteries → enter pelvic cavity to supply ovaries

ANASTOMOSES AND WATERSHED AREAS (Clinically Important)

Key Anastomoses

Watershed Zones (Vulnerable to Ischemia)

Clinical Pearl: The splenic flexure watershed is clinically the most critical — it is the most common site of ischemic colitis following aortic surgery, low-flow states, or IMA ligation.

SUMMARY TABLE

• Three unpaired anterior branches — Celiac Trunk (T12–L1), SMA (L1), and IMA (L3) — color-coded by gut territory (foregut/midgut/hindgut)
• All named branches with their organ distributions labeled
• Collateral anastomoses highlighted in gold dashed lines — gastric arcade, gastro-omental arcade, pancreaticoduodenal arcade, Marginal Artery of Drummond, and Arc of Riolan
• Watershed zones marked with warning indicators — especially the clinically critical splenic flexure (Griffiths' point) and Sudeck's point at the rectosigmoid
• Paired visceral branches — suprarenal, renal, and gonadal arteries
• A color-coded legend panel for quick reference