The Effects of Space Exploration on the Human Body

The first ever commercially flown crew of SpaceX returns to earth at the start of August, so we thought we'd take a look at a few of the effects visiting space may have made to their anatomy and physiology.

The most well-known effect of space travel is bone mineral density loss. Microgravity causes astronauts to lose 1 - 2% of it for every month that they are in space. For short term missions this is not too worrying, but a longer duration can mean that when they return back to land, their bones will be fragile and they have an increased risk of fractures. We still don't know if this density loss would ever reach a plateau or whether the bones would eventually just crumble.

Muscles have a similar fate. Due to the weightless environment, muscles no longer have to support the body's weight or movement, and they start to shrink with the tissue getting re-absorbed. Long-term missions can cause astronauts to lose up to 50% of their muscle mass!

Without gravity, the vertebra in the spine start to relax and expand, causing it to stretch and get longer. This technically makes the astronaut grow taller, potentially with a 3% increase upon their Earth-height!

Upon their return to Earth, 1 out of every 4 astronauts can experience heart palpitations or fainting if they stand for longer than 10 minutes. This is because whilst in space there is no gravity, so their cardiovascular system simply doesn’t have to work as hard to pump the blood around the body to counteract the opposite pull it generates. The changes to the cardiovascular system cause the cardiac output to reduce, the total volume of blood to lower and there may be a smaller amount of red blood cells than required.

Microgravity messes with balance and motor coordination controlled by the vestibular and sensorimotor systems, so once they are back home, astronauts may be unsteady on their feet, disorientated or suffer from motion sickness – potentially lasting for months!

Without the Earth’s atmosphere surrounding them, astronauts are exposed to space radiation. From UV rays causing skin burn, to cosmic rays mutating DNA or damaging brain cells, the full, long-term effects of this unseen energy may not be fully realised until we have been a space-faring race for a fair few more years.

Related AnatomyStuff resources:

Budget Femur Bone Model (Right)
Skeletal and Muscular Anatomy Chart / Poster
One Pound (1lb) of Muscle Model
Budget Flexible Spine Model with Pelvis
Anatomy of the Heart Chart / Poster
Budget Heart Model (2 part)

Further reading / sources:

NASA
https://www.nasa.gov/hrp/bodyinspace
Canadian Space Agency
https://www.asc-csa.gc.ca/eng/sciences/osm/concerns.asp
Human body in space
http://sitn.hms.harvard.edu/flash/2013/space-human-body/

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