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Systemic Circulation: Delivering Oxygen and Nutrients to Body Tissues

Definition

Systemic circulation is the circuit that carries oxygenated blood from the left ventricle → aorta → systemic arteries → arterioles → capillaries (exchange) → venules → systemic veins → right atrium.

Contrast with Pulmonary Circulation

  • Pulmonary: Right ventricle → pulmonary arteries → lung capillaries (gas exchange) → pulmonary veins → left atrium.
  • Systemic: Left ventricle → body capillaries (nutrient/O₂ exchange) → right atrium.

Nutrient Transport Pathway

  1. Nutrients absorbed in small intestinal capillaries → portal vein → liver (processing) → hepatic veins → IVC → right heart → pulmonary circulation → left heart → systemic arteries.
  2. At systemic capillaries, nutrients diffuse to interstitial fluid → cells.

Key Vascular Segments

  • Arteries: Conductance (elastic) → distribution (muscular) → resistance (arterioles).
  • Capillaries: Exchange vessels; continuous, fenestrated, sinusoidal types.
  • Veins: Capacitance vessels (hold ~70% blood volume); valves prevent backflow.

Regulation

  • Local metabolic control (autoregulation).
  • Neural (sympathetic vasoconstriction).
  • Hormonal (angiotensin II, ADH, ANP, NO).

Systemic circulation is the final common pathway for delivering oxygen, nutrients, hormones, and immune cells to every tissue.

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