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Human Body Study

Heart

A muscular pump, roughly fist-sized, that drives blood through the body. It beats around 100,000 times a day.

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.

Structure

Section titled “Structure”
  • Four chambers — two upper atria (receiving) and two lower ventricles (pumping).
  • Four valves — keep blood flowing one way only.
  • A wall of cardiac muscle (the myocardium), with its own blood supply via the coronary arteries.

How it works

Section titled “How it works”

A built-in pacemaker fires the rhythm; the right side pumps blood to the lungs, the left side pumps it to the rest of the body.

What it does

Section titled “What it does”

Maintains the pressure and flow that circulate blood continuously.

Key idea

Section titled “Key idea”

The heart is really two pumps in one housing, working in parallel — one for the lungs, one for the body.