How the heart works is covered in GCSE biology. Physical differences from a mechanical pump are only half the story.

The heart really differs from other mechanical pumps, in a functional sense, in that the pressure remains very low throughout, and this prevents the blood cells from being destroyed (haemolysis). This is one of the major barriers to replacing the heart with a mechanical alternative.

Pumps which do mimic the low pressure conditions tend to be too large to implant in a patient.

The atria are filled by blood entering the heart through veins, not arteries. This is quite nicely described here http://www.geocities.com/jw31645/heart-n.html

Veins 'bring' blood to the heart, arteries 'take' blood away.

Dr Matthew Benson

Dept of Pharmacology

University of Oxford

"Dr Sally Edwards, CEO of Heart Zones has proposed a set of gender specific formula for predicting Maximum Heart Rate. For males: 210 minus one half your age minus 1 per cent of total body weight plus 4. For females: 210 minus one half your age minus 1 per cent of total body weight plus 0."

"total body weight" -- in what units?