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Systemic Circulation – Core Facts

• Arteries: carry blood away from heart; veins: toward heart; capillaries: exchange; lymphatics return excess fluid.
• Aorta = largest vessel, distributes nutrient-rich blood; veins hold ≈ 60\% of blood (reservoir function).

Aorta – Segments & Key Branches

• Ascending aorta → coronary arteries (supply myocardium).
• Aortic arch → three branches:
– Brachiocephalic trunk → right common carotid + right subclavian.
– Left common carotid.
– Left subclavian.
• Descending aorta:
– Thoracic aorta (above diaphragm).
– Abdominal aorta (below diaphragm) → common iliac arteries.

Head & Neck Vessels

• Common carotids → internal (brain – Circle of Willis) & external (face/scalp) carotids.
• Vertebral arteries (from subclavians) ascend through transverse foramina → Circle of Willis.
• Primary drainage: internal, external jugular & vertebral veins → subclavian → brachiocephalic → SVC.
• Clinical: most CVAs involve middle cerebral artery of Circle of Willis → hemiplegia.

Upper Limb Pathway

• Arterial: subclavian → axillary → brachial → radial & ulnar → hand.
• Venous (deep): radial/ulnar → brachial → axillary → subclavian → brachiocephalic → SVC.
• Venous (superficial): cephalic (lateral), basilic (medial), connected by median cubital (common venipuncture).
• Brachial artery: blood-pressure site; radial artery: pulse site.

Thoracic Cavity Branches

• Visceral: pericardial, bronchial, esophageal, mediastinal.
• Parietal: posterior intercostal, subcostal, superior phrenic.
• Venous return via azygos system → SVC.

Abdominal Aorta – Branches

• Unpaired: celiac trunk, superior mesenteric, inferior mesenteric.
• Paired: inferior phrenic, suprarenal, renal, lumbar, gonadal.
• Terminal bifurcation → common iliac arteries (external & internal).

Hepatic Portal System

• Digestive veins (splenic, gastric, superior mesenteric) → hepatic portal vein → liver (detox/storage) → hepatic vein → IVC.
• Only kidneys & liver drain directly into IVC; others use portal route.

Lower Limb Vessels

• Arterial: external iliac → femoral → popliteal → anterior/posterior tibial + fibular → foot.
• Venous (superficial): dorsal venous arch → great saphenous (medial) & small saphenous (lateral) → femoral/popliteal.
• Venous (deep): fibular & tibial → popliteal → femoral → external iliac → common iliac → IVC.

Quick Recall Points

• Circle of Willis = internal carotid + vertebral contributions; collateral flow to brain.
• Celiac trunk branches: left gastric, splenic, common hepatic.
• Superior mesenteric supplies small intestine & proximal colon.
• Common order (right upper limb) : aorta → brachiocephalic trunk → right subclavian → axillary → brachial → radial/ulnar.
• Azygos vein drains thorax; hepatic vein drains processed blood to IVC.