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AORTA - THORACIC & ABDOMINAL PARTS: Detailed MBBS Notes

(Basics to Advanced | Based on Gray's Anatomy for Students)

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OVERVIEW: THE AORTA AT A GLANCE

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PART 1: THORACIC AORTA

1A. Ascending Aorta

• Arises from the left ventricle at the level of the lower border of TIV
• Enclosed within the pericardial sac
• Only branches: the two coronary arteries (right and left), which arise from the aortic sinuses (sinuses of Valsalva) just above the aortic valve cusps
• Right coronary artery - supplies SA node, AV node, right ventricle, inferior LV
• Left coronary artery - divides into LAD (anterior interventricular) and LCx (circumflex)
• The ascending aorta becomes the arch when it exits the pericardium

Mnemonic for remembering aorta segments: "All Anatomy Describes Aorta" = Ascending, Arch, Descending, Abdominal

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1B. Arch of Aorta

Three Branches from the Superior Border of the Arch

All three branches are crossed anteriorly by the left brachiocephalic vein at their origins.

Mnemonic for arch branches (Right to Left): "Big Cats Swim" = Brachiocephalic, Common carotid (left), Subclavian (left)

Variant: Thyroid Ima Artery

Ligamentum Arteriosum

• Located in the superior mediastinum
• Connects the pulmonary trunk to the arch of the aorta
• Remnant of the fetal ductus arteriosus (which allowed blood to bypass the lungs during fetal life)
• Closes after birth to form this ligament
• Clinical importance: The ligamentum arteriosum is one of the THREE fixed attachment points of the aorta

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1C. Descending Thoracic Aorta

• Situated to the left of the vertebral column superiorly
• Approaches the midline inferiorly, lying directly anterior to the lower thoracic vertebral bodies

Branches of the Descending Thoracic Aorta (Table 3.3)

Key point: The right bronchial artery arises from the third posterior intercostal artery, NOT directly from the thoracic aorta (unlike the two left bronchial arteries).

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CLINICAL CORRELATIONS - THORACIC AORTA

Three Fixed Points of the Aorta (High-Yield for Exams)

1. The aortic valve
2. The ligamentum arteriosum
3. The point of passing behind the median arcuate ligament of the diaphragm

Coarctation of the Aorta

• Congenital narrowing of the aortic lumen just distal to the left subclavian artery origin
• Blood supply to abdomen and lower limbs is diminished
• Collateral vessels develop over time through the chest wall and abdomen
• Rib notching - dilated tortuous intercostal vessels erode inferior rib margins - visible on CXR
• Cardiac effects: increased afterload → cardiac failure
• Blood pressure difference between arms and legs is a key clinical sign

Aortic Dissection

• Splitting of the aortic wall longitudinally between the intima and media
• Creates a "false channel" (true lumen + false lumen)
• Can occur anywhere along the aorta
• If in ascending aorta/arch: can disrupt coronary and cerebral arterial flow → MI or stroke
• If in abdomen: can compromise visceral vessels → bowel or renal ischemia
• Stanford Type A (involves ascending) = surgical emergency; Stanford Type B (descending only) = medical management

Aortic Arch Anomalies

• Right-sided aortic arch: aorta courses to the right of trachea and passes over right main bronchus; can be associated with dextrocardia or complete situs inversus; also associated with aberrant left subclavian artery
• Common origin of brachiocephalic trunk + left common carotid: seen in ~25% of people (a normal variant)
• Aberrant right subclavian artery (arteria lusoria): the right subclavian arises as the last branch of the arch, passes posterior to the esophagus → can cause dysphagia (dysphagia lusoria)

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PART 2: ABDOMINAL AORTA

Course and Surface Marking

• Begins: aortic hiatus of the diaphragm at the lower level of vertebra TXII (as a midline structure)
• Ends: just left of midline at the lower level of vertebra LIV, where it bifurcates
• Surface anatomy of bifurcation: approximately 2.5 cm below the umbilicus OR at the level of a line connecting the highest points of the iliac crest (intercristal plane)
• Passes downward on the anterior surface of L1-L4 vertebral bodies

Relations of the Abdominal Aorta

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Branches of the Abdominal Aorta - Overview

ABDOMINAL AORTA BRANCHES
├── VISCERAL (supplying organs)
│   ├── Unpaired (anterior)
│   │   ├── Celiac trunk (L1 - foregut)
│   │   ├── Superior mesenteric artery (L1 - midgut)
│   │   └── Inferior mesenteric artery (L3 - hindgut)
│   └── Paired (lateral/anterior)
│       ├── Middle suprarenal arteries
│       ├── Renal arteries (L1-L2)
│       └── Testicular / Ovarian arteries
├── POSTERIOR (body wall / diaphragm)
│   ├── Inferior phrenic arteries
│   ├── Lumbar arteries (4 pairs)
│   └── Median sacral artery
└── TERMINAL
    ├── Right common iliac artery
    └── Left common iliac artery

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2A. CELIAC TRUNK (Foregut Artery)

Mnemonic: "Left Spleen Company" = Left gastric, Splenic, Common hepatic

(i) Left Gastric Artery (smallest branch)

• Ascends to the cardioesophageal junction
• Sends esophageal branches upward through the esophageal hiatus (anastomoses with thoracic aorta esophageal branches)
• Turns right and descends along the lesser curvature of the stomach in the lesser omentum
• Anastomoses with right gastric artery

(ii) Splenic Artery (largest branch)

• Takes a tortuous course to the left along the superior border of the pancreas
• Travels in the splenorenal ligament to reach the hilum of the spleen
• Branches along the way:
  • Pancreatic branches - supply neck, body and tail of pancreas
  • Short gastric arteries - pass through gastrosplenic ligament to supply fundus of stomach
  • Left gastro-omental artery - runs along the greater curvature; anastomoses with right gastro-omental artery

(iii) Common Hepatic Artery (medium-sized)

• Runs to the right; divides into:
  1. Hepatic artery proper - ascends in free edge of lesser omentum; runs LEFT of bile duct, ANTERIOR to portal vein; divides into right and left hepatic arteries near porta hepatis; right hepatic gives the cystic artery to the gallbladder
  2. Gastroduodenal artery - descends posterior to the first part of the duodenum; divides into right gastro-omental artery and superior pancreaticoduodenal artery

Clinical note: In some individuals, the right hepatic artery arises aberrantly from the SMA (important in liver surgery and transplantation)

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2B. SUPERIOR MESENTERIC ARTERY (SMA - Midgut Artery)

Arterial Arcades - High Yield

• Jejunal and ileal arteries form anastomosing arcades in the mesentery before giving off vasa recta (straight arteries) to the bowel wall
• Jejunum: 1-2 arcades; long, closely spaced vasa recta → narrow windows in mesentery
• Ileum: 3-5 arcades; short, widely spaced vasa recta → low, broad windows in mesentery
• This difference is used to distinguish jejunum from ileum during surgery

SMA Syndrome: The SMA passes at an angle over the duodenum; rarely, it can compress the third part of the duodenum causing vomiting (treated with repositioning or surgery)

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2C. INFERIOR MESENTERIC ARTERY (IMA - Hindgut Artery)

Marginal Artery of Drummond

• A continuous arterial arcade formed by anastomoses between branches of the SMA and IMA, running along the inner border of the colon from the ileocecal junction to the rectosigmoid junction
• Clinically important as a collateral pathway when either the SMA or IMA is occluded

Critical Point (Sudeck's Point)

• The anastomosis between the last sigmoid artery and the superior rectal artery may be poor near the rectosigmoid junction
• This area (Sudeck's critical point) is at risk of ischemia after IMA ligation in colorectal surgery

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2D. PAIRED VISCERAL BRANCHES

Renal Arteries (L1-L2)

• Arise as lateral branches just inferior to the SMA, between L1 and L2
• Right renal artery is longer - passes posterior to the IVC, right renal vein, head of pancreas, and descending duodenum
• Left renal artery is shorter - passes posterior to the left renal vein and the body of the pancreas
• Each artery gives off an inferior suprarenal artery before entering the kidney at the hilum
• The renal artery divides into an anterior and posterior division, then into segmental arteries (5 segments - each is an end artery = no anastomosis → infarction if blocked)

Middle Suprarenal Arteries

• Small lateral branches arising just above the renal arteries
• Part of the triple arterial supply to the adrenal gland:
  1. Superior suprarenal artery (from inferior phrenic)
  2. Middle suprarenal artery (from aorta)
  3. Inferior suprarenal artery (from renal artery)

Gonadal Arteries (Testicular / Ovarian)

• Arise as anterior branches below the renal arteries
• Long slender vessels that pass downward and laterally on the anterior surface of psoas major
• Cross over the ureter ("water under the bridge" - ureter crosses anterior to gonadal vessels)
• In males: pass through the inguinal canal into the scrotum as testicular arteries
• In females: enter the pelvic cavity and pass in the suspensory ligament of the ovary as ovarian arteries
• Embryological note: The gonads develop retroperitoneally at L1 level, which explains the long course of these vessels

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2E. POSTERIOR BRANCHES

Inferior Phrenic Arteries

• Arise from the abdominal aorta immediately below the aortic hiatus (or occasionally from the celiac trunk)
• Pass upward to supply the inferior surface of the diaphragm
• Give superior suprarenal branches to the adrenal gland

Lumbar Arteries (4 pairs)

• Arise from the posterior surface of the abdominal aorta in 4 pairs (corresponding to L1-L4)
• Each lumbar artery passes posteriorly around the sides of the vertebral bodies
• Each gives off a dorsal branch (supplies back muscles and skin) and a spinal branch (enters the intervertebral foramen to supply the spinal cord and meninges)
• Clinical note: Lumbar arteries are at risk during abdominal aortic aneurysm repair; their spinal branches can supply the artery of Adamkiewicz

Median Sacral Artery

• Single posterior branch arising just above the aortic bifurcation at LIV
• Passes inferiorly across the lumbar vertebrae, sacrum, and coccyx
• A remnant of the embryonic caudal aorta

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2F. TERMINAL BRANCHES

• Right common iliac artery
• Left common iliac artery

• External iliac artery → becomes the femoral artery (lower limb supply)
• Internal iliac artery → pelvic viscera, perineum, gluteal region

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SUMMARY COMPARISON TABLE: FOREGUT vs MIDGUT vs HINDGUT SUPPLY

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HIGH-YIELD CLINICAL TOPICS (Advanced Level)

Abdominal Aortic Aneurysm (AAA)

• Defined as aortic diameter > 3 cm (or > 1.5x normal)
• Most are infrarenal (between renal arteries and bifurcation)
• Risk factors: atherosclerosis, hypertension, smoking, male sex, family history
• Clinically: pulsatile abdominal mass, abdominal/back pain; rupture = life-threatening emergency
• Screening: Ultrasound once in men aged 65 (smokers/ex-smokers)
• Surgery indicated when diameter > 5.5 cm or growing > 1 cm/year

Aortic Occlusion (Leriche Syndrome)

• Chronic occlusion at the aortic bifurcation
• Classic triad: (1) Bilateral hip/buttock/thigh claudication, (2) Impotence, (3) Absent femoral pulses

Celiac Artery Compression Syndrome (Median Arcuate Ligament Syndrome)

• Compression of the celiac trunk by the median arcuate ligament of the diaphragm
• Presents with postprandial epigastric pain, weight loss, and an epigastric bruit

Mesenteric Ischemia

• Acute: Usually from SMA embolus (from cardiac thrombus) or thrombosis - surgical/interventional emergency
• Chronic: Progressive occlusion ("intestinal angina") - postprandial pain, weight loss, food fear
• IMA is less commonly implicated as collateral supply is rich

Renovascular Hypertension

• Renal artery stenosis (usually atherosclerosis in adults, fibromuscular dysplasia in young women) reduces renal blood flow → activates RAAS → hypertension
• Diagnosed by Doppler US, CT angiography, or renal arteriography

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EMBRYOLOGICAL NOTES

• The aorta develops from the paired dorsal aortae that fuse in the embryo
• Celiac trunk, SMA, and IMA represent persistent vitelline arteries supplying the yolk sac-derived gut
• The ductus arteriosus connects the pulmonary trunk to the aortic arch in the fetus; after birth it closes → ligamentum arteriosum
• Failure to close = Patent Ductus Arteriosus (PDA) - a congenital heart disease
• Coarctation of the aorta occurs because of abnormal development at the site of the ductus arteriosus

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QUICK REVISION MNEMONICS

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AORTA - Complete Stepwise Branch Tree

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THORACIC AORTA

SEGMENT 1: ASCENDING AORTA

ASCENDING AORTA
├── Right Coronary Artery (RCA)
│   ├── Conus artery (to right ventricular outflow tract)
│   ├── SA nodal artery (60% of people)
│   ├── Right marginal artery
│   ├── AV nodal artery (80% of people)
│   └── Posterior descending artery (PDA) - in right dominant circulation
│
└── Left Coronary Artery (LCA)
    ├── Left Anterior Descending (LAD)
    │   ├── Diagonal branches (D1, D2)
    │   └── Septal perforators
    └── Left Circumflex (LCx)
        ├── Obtuse marginal branches (OM1, OM2)
        └── SA nodal artery (40% of people)

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SEGMENT 2: ARCH OF AORTA

ARCH OF AORTA
├── 1st Branch → BRACHIOCEPHALIC TRUNK (largest)
│   ├── Right Common Carotid Artery
│   │   ├── Right Internal Carotid Artery
│   │   │   ├── Ophthalmic artery
│   │   │   ├── Anterior cerebral artery
│   │   │   ├── Middle cerebral artery
│   │   │   └── Posterior communicating artery
│   │   └── Right External Carotid Artery
│   │       ├── Superior thyroid artery
│   │       ├── Ascending pharyngeal artery
│   │       ├── Lingual artery
│   │       ├── Facial artery
│   │       ├── Occipital artery
│   │       ├── Posterior auricular artery
│   │       ├── Superficial temporal artery
│   │       └── Maxillary artery
│   └── Right Subclavian Artery
│       ├── Vertebral artery
│       ├── Internal thoracic (mammary) artery
│       │   ├── Anterior intercostal arteries (upper 6 spaces)
│       │   ├── Pericardiophrenic artery
│       │   └── Musculophrenic artery
│       ├── Thyrocervical trunk
│       │   ├── Inferior thyroid artery
│       │   ├── Suprascapular artery
│       │   └── Transverse cervical artery
│       ├── Costocervical trunk
│       │   ├── Supreme intercostal artery (→ 1st & 2nd posterior intercostals)
│       │   └── Deep cervical artery
│       └── Dorsal scapular artery
│
├── 2nd Branch → LEFT COMMON CAROTID ARTERY
│   ├── Left Internal Carotid Artery
│   │   └── (same branches as right - cerebral circulation)
│   └── Left External Carotid Artery
│       └── (same 8 branches as right side)
│
└── 3rd Branch → LEFT SUBCLAVIAN ARTERY
    └── (same branches as right subclavian)

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SEGMENT 3: DESCENDING THORACIC AORTA

DESCENDING THORACIC AORTA (T4 → T12)
│
├── Pericardial branches (small, to posterior pericardium)
│
├── Bronchial arteries
│   ├── Left Superior Bronchial artery (from thoracic aorta)
│   ├── Left Inferior Bronchial artery (from thoracic aorta)
│   └── Right Bronchial artery (from 3rd posterior intercostal artery)
│
├── Esophageal branches (4-5 vessels, anterior aspect)
│   ├── Superiorly anastomose with esophageal br. of inferior thyroid artery
│   └── Inferiorly anastomose with esophageal br. of left gastric artery
│
├── Mediastinal branches (to lymph nodes, nerves, areolar tissue)
│
├── Posterior Intercostal Arteries — 9 PAIRS (spaces 3 to 11)
│   Each intercostal artery gives:
│   ├── Dorsal branch
│   │   ├── Spinal branch (to spinal cord via intervertebral foramen)
│   │   └── Muscular/cutaneous branches (back muscles & skin)
│   ├── Collateral branch (runs along upper border of rib below)
│   └── Lateral cutaneous branch
│       [Note: Spaces 1 & 2 → from Supreme Intercostal Artery (costocervical trunk)]
│
├── Superior Phrenic Arteries (paired, small)
│   └── Posterior superior surface of diaphragm
│
└── Subcostal Arteries (1 pair — below rib 12)
    └── Posterior abdominal wall

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ABDOMINAL AORTA

SEGMENT 4: ABDOMINAL AORTA (T12 → L4)

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UNPAIRED ANTERIOR BRANCHES

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
CELIAC TRUNK  (L1 — FOREGUT)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
│
├── LEFT GASTRIC ARTERY (smallest)
│   ├── Esophageal branches (→ anastomose with thoracic aorta esophageal br.)
│   └── Gastric branches (lesser curvature, both surfaces)
│       └── Anastomoses with RIGHT GASTRIC ARTERY
│
├── SPLENIC ARTERY (largest, tortuous)
│   ├── Pancreatic branches
│   │   ├── Dorsal pancreatic artery
│   │   ├── Great pancreatic artery (arteria pancreatica magna)
│   │   └── Caudal pancreatic artery
│   ├── Short gastric arteries (5-7 branches → fundus of stomach)
│   └── Left Gastro-omental (gastro-epiploic) artery
│       └── Anastomoses with RIGHT GASTRO-OMENTAL artery (along greater curvature)
│
└── COMMON HEPATIC ARTERY
    │
    ├── HEPATIC ARTERY PROPER
    │   ├── Right Hepatic Artery
    │   │   ├── Cystic artery → gallbladder
    │   │   └── Right lobe of liver
    │   └── Left Hepatic Artery
    │       └── Left lobe of liver
    │
    └── GASTRODUODENAL ARTERY
        ├── Right Gastro-omental (gastro-epiploic) artery
        │   └── Greater curvature of stomach (right side)
        └── Superior Pancreaticoduodenal artery
            ├── Anterior superior pancreaticoduodenal artery
            └── Posterior superior pancreaticoduodenal artery
                └── Anastomose with INFERIOR pancreaticoduodenal
                    branches from SMA (forming pancreaticoduodenal arcade)

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━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
SUPERIOR MESENTERIC ARTERY — SMA  (L1 — MIDGUT)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
│
├── INFERIOR PANCREATICODUODENAL ARTERY (1st branch)
│   ├── Anterior inferior pancreaticoduodenal artery
│   └── Posterior inferior pancreaticoduodenal artery
│       └── Anastomose with SUPERIOR pancreaticoduodenal arteries (from celiac)
│
├── JEJUNAL ARTERIES (left side — 4-6 branches)
│   └── Form arterial arcades → Vasa recta → jejunum
│       [1-2 arcades; long closely-spaced vasa recta]
│
├── ILEAL ARTERIES (left side — 9-13 branches)
│   └── Form arterial arcades → Vasa recta → ileum
│       [3-5 arcades; short widely-spaced vasa recta]
│
├── ILEOCOLIC ARTERY (right side — most distal right branch)
│   ├── Ileal branch (→ anastomoses with SMA)
│   ├── Anterior cecal artery
│   ├── Posterior cecal artery
│   ├── Appendicular artery → appendix
│   └── Colic branch → ascending colon (lower part)
│
├── RIGHT COLIC ARTERY (right side)
│   ├── Ascending branch → anastomoses with middle colic
│   └── Descending branch → anastomoses with ileocolic
│       → Supply: ascending colon
│
└── MIDDLE COLIC ARTERY (right side — first right branch)
    ├── Right branch → anastomoses with right colic
    └── Left branch → anastomoses with left colic (IMA)
        → Supply: proximal 2/3 of transverse colon
        [Forms part of MARGINAL ARTERY OF DRUMMOND]

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━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
INFERIOR MESENTERIC ARTERY — IMA  (L3 — HINDGUT)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
│
├── LEFT COLIC ARTERY (1st branch)
│   ├── Ascending branch
│   │   ├── Upper descending colon
│   │   ├── Distal transverse colon
│   │   └── Anastomoses with MIDDLE COLIC (SMA)
│   └── Descending branch
│       ├── Lower descending colon
│       └── Anastomoses with 1st sigmoid artery
│
├── SIGMOID ARTERIES (2-4 branches)
│   ├── Lowest descending colon
│   ├── Sigmoid colon
│   ├── Anastomose superiorly with left colic branches
│   └── Anastomose inferiorly with superior rectal artery
│
└── SUPERIOR RECTAL ARTERY (terminal branch of IMA)
    ├── Descends into pelvis in sigmoid mesocolon
    ├── Crosses left common iliac vessels
    ├── Divides at SIII → right and left terminal branches
    └── Anastomoses:
        ├── Middle rectal artery (from internal iliac)
        └── Inferior rectal artery (from internal pudendal)

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PAIRED LATERAL BRANCHES

PAIRED LATERAL BRANCHES
│
├── MIDDLE SUPRARENAL ARTERIES (paired — just above renal arteries)
│   └── Adrenal glands
│       [triple supply: superior suprarenal (inf. phrenic) +
│        middle suprarenal (aorta) + inferior suprarenal (renal artery)]
│
├── RENAL ARTERIES (paired — L1/L2, below SMA)
│   ├── Right renal artery (longer — passes behind IVC)
│   └── Left renal artery (shorter)
│   Each gives:
│   ├── Inferior suprarenal artery → adrenal gland
│   ├── Ureteric branches → upper ureter
│   └── Anterior division + Posterior division
│       └── 5 Segmental arteries (end arteries — no anastomosis)
│           ├── Apical
│           ├── Upper
│           ├── Anterior inferior
│           ├── Posterior
│           └── Lower
│
└── GONADAL ARTERIES (paired — below renal arteries)
    ├── In Males → Testicular arteries
    │   ├── Pass through inguinal canal
    │   └── Supply testes + epididymis
    └── In Females → Ovarian arteries
        ├── Pass in suspensory ligament of ovary
        └── Supply ovaries + uterine tubes
            [Anastomose with uterine artery — branch of internal iliac]

---

POSTERIOR BRANCHES

POSTERIOR BRANCHES
│
├── INFERIOR PHRENIC ARTERIES (paired)
│   ├── Supply inferior surface of diaphragm
│   └── Superior suprarenal branches → adrenal glands
│
├── LUMBAR ARTERIES — 4 PAIRS (L1-L4)
│   Each lumbar artery gives:
│   ├── Dorsal branch
│   │   ├── Spinal branch (→ spinal cord via intervertebral foramen)
│   │   │   [L1 branch may be the Artery of Adamkiewicz
│   │   │    — main blood supply to lower 2/3 of spinal cord]
│   │   └── Muscular/cutaneous branches (back muscles & skin)
│   └── Abdominal wall branches
│
└── MEDIAN SACRAL ARTERY (single — just above bifurcation)
    └── Sacrum, coccyx, posterior rectum

---

TERMINAL BRANCHES

TERMINAL BRANCHES (at L4 bifurcation)
│
├── RIGHT COMMON ILIAC ARTERY
│   ├── Right External Iliac Artery
│   │   └── → Femoral Artery (below inguinal ligament)
│   └── Right Internal Iliac Artery (Hypogastric)
│       ├── Anterior division
│       │   ├── Superior vesical artery
│       │   ├── Inferior vesical artery (male) / Vaginal artery (female)
│       │   ├── Middle rectal artery
│       │   ├── Uterine artery (female)
│       │   ├── Obturator artery
│       │   ├── Internal pudendal artery
│       │   │   └── Inferior rectal artery
│       │   └── Inferior gluteal artery
│       └── Posterior division
│           ├── Iliolumbar artery
│           ├── Lateral sacral artery
│           └── Superior gluteal artery
│
└── LEFT COMMON ILIAC ARTERY
    └── (same divisions as right)

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COMPLETE COLUMNAR SUMMARY

AORTA
│
├── ASCENDING AORTA
│   ├── Right Coronary Artery
│   └── Left Coronary Artery (LAD + LCx)
│
├── ARCH OF AORTA
│   ├── Brachiocephalic Trunk → R. Common Carotid + R. Subclavian
│   ├── Left Common Carotid Artery
│   └── Left Subclavian Artery
│
├── DESCENDING THORACIC AORTA
│   ├── Pericardial branches
│   ├── Bronchial arteries (L×2, R×1)
│   ├── Esophageal branches (4-5)
│   ├── Mediastinal branches
│   ├── Posterior Intercostal arteries (9 pairs)
│   ├── Superior Phrenic arteries
│   └── Subcostal arteries (1 pair)
│
└── ABDOMINAL AORTA
    ├── Celiac Trunk → L. Gastric + Splenic + Common Hepatic
    ├── Superior Mesenteric Artery → Inf. Pancreat. +
    │   Jejunal + Ileal + Ileocolic + R. Colic + M. Colic
    ├── Middle Suprarenal arteries (paired)
    ├── Renal arteries (paired)
    ├── Gonadal arteries (paired)
    ├── Inferior Phrenic arteries (paired)
    ├── Lumbar arteries (4 pairs)
    ├── Inferior Mesenteric Artery → L. Colic +
    │   Sigmoid arteries + Superior Rectal
    ├── Median Sacral artery
    └── BIFURCATION (L4)
        ├── R. Common Iliac → R. External + R. Internal Iliac
        └── L. Common Iliac → L. External + L. Internal Iliac

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Tip for exams: Remember the order of abdominal aorta branches top to bottom using - "I Can't See My Testis Going In Lumbar Mess" = Inferior phrenic, Celiac, (Superior) Mesenteric, Middle suprarenal, Testicular/ovarian, Gonadal, Inferior phrenic (already counted), Lumbar arteries, Mesenteric inferior, (Median) Sacral