3 ms·

Your Body Is Younger Than You Think (2005)

64 points by orcul 7y ago

rdiddly 7y ago
You could also say my body is billions of years old because that's the age of most of my atoms. In every way except the one that counts, it seems I'm not my age!
schwartzworld 7y ago
Ah yes, the old Ship of Theseus thought experiment. If someone went around collecting all the molecules lost in my sweat, spit, urine and feces, and built a new person out of it, which one is me?
- ahelwer 7y ago
  Easy but uncomfortable answer: neither, because "you" don't exist.
  - vokep 7y ago
    Harder to explain but more comfortable answer: neither, because "you" don't exist in your body, but the entire universe, and "you" as far as you're concerned, is the pattern emerging "on top" of the molecules that make "you".
glitchc 7y ago
This article is out of date. More research indicates that neuroplasticity is a measurable phenomenon and the cortex does indeed create new brain cells.
jessriedel 7y ago
> The inner lens cells form in the embryo and then lapse into such inertness for the rest of their owner's lifetime that they dispense altogether with their nucleus and other cellular organelles. Does anyone know what metabolic processes these cells continue to perform, if any? If they literally drop their nucleus and other organelles, is there anything left besides the cell membrane, cytoskeleton, and cytoplasm? How do they repair damage, and in what sense are they a living cell rather than just an inert husk like the dead cells in the cuticle of hair? I believe "inner lens cells" refers to the lens fibers, but this is all Wikipedia had to say: > New lens fibers are generated from the equatorial cells of the lens epithelium, in a region referred to as the germinative zone. The lens epithelial cells elongate, lose contact with the capsule and epithelium, synthesize crystallin, and then finally lose their nuclei (enucleate) as they become mature lens fibers.... > Another important factor in maintaining the transparency of the lens is the absence of light-scattering organelles such as the nucleus, endoplasmic reticulum, and mitochondria within the mature lens fibers. Lens fibers also have a very extensive cytoskeleton that maintains the precise shape and packing of the lens fibers; disruptions/mutations in certain cytoskeletal elements can lead to the loss of transparency https://en.wikipedia.org/wiki/Lens_(anatomy) https://en.wikipedia.org/wiki/Lens_(anatomy)
- skadamou 7y ago
  My understanding is that most of the metabolic activity required in the lens takes place in the germinative zone you mentioned and then proteins necessary for lens health diffuse through abundant gap junctions from the lens cortex into the lens core. Take all of that with a grain of salt though. I haven't studied this in depth but I did work in a lab that studied gap junctions of the lens in undergrad Also, here is an NCBI article all about the lens: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5538311/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5538311/
  - jessriedel 7y ago
    Thanks!

64 points by orcul 7y ago

You could also say my body is billions of years old because that's the age of most of my atoms. In every way except the one that counts, it seems I'm not my age!

schwartzworld 7y ago

Ah yes, the old Ship of Theseus thought experiment. If someone went around collecting all the molecules lost in my sweat, spit, urine and feces, and built a new person out of it, which one is me?

ahelwer 7y ago
Easy but uncomfortable answer: neither, because "you" don't exist.
- vokep 7y ago
  Harder to explain but more comfortable answer: neither, because "you" don't exist in your body, but the entire universe, and "you" as far as you're concerned, is the pattern emerging "on top" of the molecules that make "you".

glitchc 7y ago

This article is out of date. More research indicates that neuroplasticity is a measurable phenomenon and the cortex does indeed create new brain cells.

jessriedel 7y ago

> The inner lens cells form in the embryo and then lapse into such inertness for the rest of their owner's lifetime that they dispense altogether with their nucleus and other cellular organelles. Does anyone know what metabolic processes these cells continue to perform, if any? If they literally drop their nucleus and other organelles, is there anything left besides the cell membrane, cytoskeleton, and cytoplasm? How do they repair damage, and in what sense are they a living cell rather than just an inert husk like the dead cells in the cuticle of hair? I believe "inner lens cells" refers to the lens fibers, but this is all Wikipedia had to say: > New lens fibers are generated from the equatorial cells of the lens epithelium, in a region referred to as the germinative zone. The lens epithelial cells elongate, lose contact with the capsule and epithelium, synthesize crystallin, and then finally lose their nuclei (enucleate) as they become mature lens fibers.... > Another important factor in maintaining the transparency of the lens is the absence of light-scattering organelles such as the nucleus, endoplasmic reticulum, and mitochondria within the mature lens fibers. Lens fibers also have a very extensive cytoskeleton that maintains the precise shape and packing of the lens fibers; disruptions/mutations in certain cytoskeletal elements can lead to the loss of transparency https://en.wikipedia.org/wiki/Lens_(anatomy) https://en.wikipedia.org/wiki/Lens_(anatomy)

skadamou 7y ago
My understanding is that most of the metabolic activity required in the lens takes place in the germinative zone you mentioned and then proteins necessary for lens health diffuse through abundant gap junctions from the lens cortex into the lens core. Take all of that with a grain of salt though. I haven't studied this in depth but I did work in a lab that studied gap junctions of the lens in undergrad Also, here is an NCBI article all about the lens: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5538311/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5538311/
- jessriedel 7y ago
  Thanks!