The human heart: An introduction

Atrium [ey-tree-uh m] noun.

Origin Latin for “entrance hall” 1570-80. Either of the two upper chambers on each side of the heart that receive blood from veins and in turn force it into the ventricles.

Ventricle [ven-tri-kuh l] noun.

Origin Latin for “little belly” 1350-1400. Either of the two lower chambers on each side of the heart that receive blood from the atria and in turn force it into the arteries.

How big?

The heart is roughly the size of two adult fists.

Where exactly?

The heart is actually in the middle of your chest and not to the left.

Lub dub, lub dub, lub dub

The heartbeat is simply the sound of its valves opening and closing.

Facts of the heart

• The king of hearts is the only monarch without a moustache in a standard pack of cards.
• There are 150 heart attacks each day in Australia.
• In Australia it is recommended that adults consume at least 500mg of omega-3 every day to help maintain heart health.
• Every 53 minutes an Australian dies from a heart attack.
• Laughter can actually relax your arteries. Your body responds to a good chuckle by lowering levels of the stress hormone cortisol. This can decrease your blood pressure.
• A study in The European Journal of Epidemiology found the risk of heart attacks was 20% greater on Monday for adult men and 15% for adult women.
• There are 96 million kilometres of blood vessels in your body, which is enough to wrap around the world twice, and then some.
• Men have an average of 70 heartbeats per minute. Women average 78.
• The aorta, the largest artery in the body is about the diameter of a garden hose.
• Capillaries are so small it takes ten of them to equal the thickness of a human hair.
• Your corneas are the only body parts that get no blood from the heart.
• Right now, your heart is pumping five and a half litres of blood around your body. A newborn has only one cup’s worth.
• When relaxed, 16 seconds is all it takes for your blood to travel from your heart to your big toe and back.
• It takes three weeks from conception until the heart starts beating.
• Adults who sit less throughout the day have a lower risk of early death particularly from cardiovascular disease.

Which animal has the biggest heart?

Hummingbird

Heart: similar size to an eraser on a pencil tip. Has the largest heart of any animal relative to its tiny body mass.

Chambers: four

Python

Heart: just over a centimetre in size, but balloons to almost double this after a mighty feast, to help speed up digestion.

Chambers: three

Giraffe

Heart: the largest heart of all land mammals, about 60 centimetres long. Heart beats around 170 times per minute to pump blood up its long neck.

Chambers: four

Elephant

Heart: weighs between 20 – 30 kilos, but only beats around 30 times a minute, making the elephant the largest animal with the lowest heart rate.

Chambers: four

Earthworm

Heart: technically, the earthworm has no heart, but its five aortic arches help pump blood around the body.

Chambers: none

Human

Heart: around the size of two clenched fists, or nine centimetres wide, with male hearts weighing slightly more than female hearts.

Chambers: four

Rabbit

Heart: it makes up a tiny part of its body weight, but rabbit hearts can beat up to 300 times per minute, meaning they can easily die of shock.

Chambers: four

Polar bear

Heart: a similar size to a cricket ball, polar bear hearts are about 20 centimetres wide. Their heartbeat slows from 40 to 27 beats per minute when hibernating.

Chambers: four

Pig

Heart: practically the same size as a human’s, pig hearts have been successfully transplanted into apes and pig valves are used in human transplants.

Chambers: four

Horse

Heart: around three times the size of a human’s and about the size of a melon, a running horse’s heart can clock 240 beats per minute.

Chambers: four

Dog

Heart: the heart size of a dog differs greatly by breed and gender, but in general terms, smaller dogs tend to have zippier heart rates than larger dogs.

Chambers: four

Blue whale

Heart: around the size of a small car, whale hearts need to pump about 7,000 litres of blood, compared to five and a half litres in a human.

Chambers: four