the astronaut heart and muscles and bones shrink and get weaker ...this because:
the earth's gravitational pull is strong so the heart pumps blood harder than it needs to in space so when a astronaut is in orbit it doesn't need to work so hard so they shrink.
hope this helps.
What happens to the bones when muscle shortening
Skeletal muscle tissue is striated muscle tissue connected to bones.
Muscle
ligaments attach bone to bone and tendons attach bone to muscle
In space, the lack of gravity-induced pressure on your bones leads to decreased bone density because your body does not need to support its weight in the same way as it does on Earth. As a result, astronauts in space experience bone loss due to reduced mechanical stress on their bones, which can lead to weakened bones and an increased risk of fractures.
The bones itself do not move, but it's the muscle that moves it.
What happens to your bones when you are weightless, is that your bones will get weaker and weaker. That is why everyday, astronauts, have to spend two hours on a treadmill everyday of there space expedition.
ligaments. tendons are muscle attached to muscle.
Astronauts' muscles atrophy in space due to the decreased work they do without Earth's gravity.
skeletal muscle Joints
Smooth Muscle
hi hows your muscle