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Human Body Study

Cardiovascular System

The body’s transport network — a pump, a fleet of vessels, and the fluid they circulate.

The closed-loop circulation A four-chambered heart at the centre, with a pulmonary loop to the lungs above and a systemic loop to a body capillary bed below; red vessels carry oxygen-rich blood, blue vessels oxygen-poor. A separate inset shows blood at a vessel cross-section. Each label links to the article for that part. Blood RA LA RV LV Heart Arteries Capillaries Veins The closed-loop circulation — schematic, not to scale.

Main parts

Section titled “Main parts”
  • Heart — the four-chambered muscular pump that drives circulation.
  • Arteries — carry blood away from the heart under high pressure.
  • Veins — return blood to the heart; the body’s blood reservoir.
  • Capillaries — microscopic vessels where exchange with tissues happens.
  • Blood — the fluid itself: red cells, white cells, platelets, and plasma.

What it does

Section titled “What it does”
  • Delivery — brings oxygen and nutrients to every cell.
  • Removal — carries away carbon dioxide and waste.
  • Distribution — moves hormones, immune cells, and heat around the body.

Key idea

Section titled “Key idea”

The system is a closed loop under pressure. Roughly 100,000 heartbeats a day keep blood moving so that no cell — none of them more than a hair’s width from a capillary — goes without supply.