5 ms·

Many of the dissolved ions are used by organisms in the ocean and are removed from the water... The two ions that are present most often in seawater are chlori

Many of the dissolved ions are used by organisms in the ocean and are removed from the water... The two ions that are present most often in seawater are chloride and sodium. These two make up over 90% of all dissolved ions in seawater. The other ten percent are micronutrients that are also essential to life. Most land animals have a skeleton not just to provide physical scaffolding to hang tissue on but because we need a store of calcium to mediate blood pH, something sea life doesn't require thanks to those minerals in the water. That's why you can have sharks which are mostly supported by cartilage with one set of bones: Their jaws.

Blahah 3y ago
I have long known sharks have cartilaginous skeletons but only just wondered whether that means shark bodies are squishy like human ears? Like if you hugged a shark would it deform?
- DoreenMichele 3y ago
  I don't know but I wouldn't recommend trying it, at least not without wearing chain mail. Their skin is abrasive if you hug them and call them George and rub their skin backwards.
- hn_throwaway_99 3y ago
  No. The human nose is mostly cartilage and it's hard.
  - edgyquant 3y ago
    It’s pretty soft compared to bone. I can push mine half way down to the skin.
    - deleted 3y ago
      [deleted]
  - Calavar 3y ago
    The lower half of the nose is cartilage and is pretty soft. The upper half of the nose hard and is bone.
    - BuildTheRobots 3y ago
      This is probably a stupid question, but if the upper half of the nose is bone, why does a human skull seem to always have a hole where the nose is?
      - thfuran 3y ago
        Because the bottom half isn't bone and the whole thing is hollow.
      - AlotOfReading 3y ago
        That's where the cartilage was. You can find that hole in your own skull easily enough. There should be a small bump midway up your nasal ridge. That point is called the rhinion. Everything above it is laying on your skull. The parts of the nose below it cover your nasal cavity.
      - Retric 3y ago
        Anatomically correct skulls have an hole where the bottom of your nose is and the eyes are both smaller and higher up than you probably think. https://en.wikipedia.org/wiki/Orbit_(anatomy)#/media/File:Eye_orbit_anatomy_anterior2.jpg https://en.wikipedia.org/wiki/Orbit_(anatomy)#/media/File:Ey... Looking at yourself in a mirror, if you hold your finger over the top of your nose your eyes will see under your finger. Move your finger just low enough so you’re seeing over it and you should be touching the bottom of your nasal bone. At that point your nose should be more than a finger width froward from the bottom of your orbital socket which is where the hole in skulls starts in those skulls.
      - Calavar 3y ago
        Look at a picture of a skull in profile. You'll see that there is half a nose, not no nose. That half of the nose that you can see is the bony part. The missing half is the cartilaginous part. Why is there a hole? Because your nasal canal extends inside your skull to connect with the back of your throat. I guess I don't fully understand the question there.
- Moto7451 3y ago
  While you can’t hug them, see if your nearest aquarium has a touch tank experience. Usually they do those with rays/skates but you can also find them with Nurse sharks. Either way, you’ll literally get a feel for their composition. From memory it’s more like the stiff parts of your nose running near/along the bone and unlike your ears in any way.
- darkerside 3y ago
  My guess is that, yeah, if you empty them of water
gwerbret 3y ago
> we need a store of calcium to mediate blood pH Blood pH is regulated mainly by dissolved carbon dioxide and bicarbonate [1]. There's an order of magnitude less calcium in the blood, usually in the form of calcium phosphate, than either of those, and the amount is extremely tightly regulated within a very narrow concentration range -- far too narrow to have a notable effect on pH. [1]: https://www.ncbi.nlm.nih.gov/books/NBK482291 https://www.ncbi.nlm.nih.gov/books/NBK482291
- DoreenMichele 3y ago
  The majority of calcium ions within the cell are bound to intracellular proteins, leaving a minority freely dissociated. When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a cardiomyocyte during each cardiac cycle becomes bound to calcium buffers, creating a relatively small change in free calcium. https://en.m.wikipedia.org/wiki/Calcium_buffering https://en.m.wikipedia.org/wiki/Calcium_buffering I raised and homeschooled two kids and watched a lot of when dinosaurs ruled the earth type stuff. That's my source for the idea that a store of calcium was critical for allowing life to leave the ocean and I've tried repeatedly to search for additional info on this and can never find it. I have no problem imagining that calcium is essential for buffering pH in land mammals and that free calcium ions simultaneously are tightly regulated and not directly used to move that number for the blood in short time frames. That actually fits perfectly well with my mental models that cellular acidosis is a more fundamental problem that fuels acidosis of bodily fluids. If anyone has any good sources that might clarify this relationship for me, that would be cool.
  - Retric 3y ago
    > calcium is essential for buffering pH Except that’s not what’s going on. The Wikipedia article lays it out. The amount of hydrogen ions someplace is what PH means, so controlling PH is controlling the number of hydrogen ions. The same thing happens with calcium, but rather than doing the buffering it’s the number of calcium ions being controlled. Calcium buffering is controlling the number of calcium ions. > Calcium buffering describes the processes which help stabilise the concentration of free calcium ions within cells, in a similar manner to how pH buffers maintain a stable concentration of hydrogen ions.[1] The majority of calcium ions within the cell are bound to intracellular proteins, leaving a minority freely dissociated.[2] When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a cardiomyocyte during each cardiac cycle becomes bound to calcium buffers, creating a relatively small change in free calcium.[2]
quickthrower2 3y ago
Thanks, that is fascinating. The amount of gold/silver is too. Even just the amount of salt. Measure in parts per 1000! I like having a wow moment about something we take for granted.
eru 3y ago
> Most land animals have a skeleton [...] Most land animals don't have a skeleton. Most land animals are insects and similar critters.
- medstrom 3y ago
  They have exoskeletons, which still serve the stated purposes.
  - eru 3y ago
    Those exoskeletons are made of chitin. Chitin is a carbohydrate. It doesn't really have much to do with calcium.
thaumasiotes 3y ago
> Most land animals have a skeleton not just to provide physical scaffolding to hang tissue on but because we need a store of calcium to mediate blood pH, something sea life doesn't require thanks to those minerals in the water. That's why you can have sharks which are mostly supported by cartilage Well, the other reason sea life doesn't require rigid bones is that water provides a lot more buoyancy than air. Jellyfish work fine in the water; on land they're immobile puddles of glop.

Blahah 3y ago

I have long known sharks have cartilaginous skeletons but only just wondered whether that means shark bodies are squishy like human ears? Like if you hugged a shark would it deform?

DoreenMichele 3y ago
I don't know but I wouldn't recommend trying it, at least not without wearing chain mail. Their skin is abrasive if you hug them and call them George and rub their skin backwards.
hn_throwaway_99 3y ago
No. The human nose is mostly cartilage and it's hard.
- edgyquant 3y ago
  It’s pretty soft compared to bone. I can push mine half way down to the skin.
  - deleted 3y ago
    [deleted]
- Calavar 3y ago
  The lower half of the nose is cartilage and is pretty soft. The upper half of the nose hard and is bone.
  - BuildTheRobots 3y ago
    This is probably a stupid question, but if the upper half of the nose is bone, why does a human skull seem to always have a hole where the nose is?
    - thfuran 3y ago
      Because the bottom half isn't bone and the whole thing is hollow.
    - AlotOfReading 3y ago
      That's where the cartilage was. You can find that hole in your own skull easily enough. There should be a small bump midway up your nasal ridge. That point is called the rhinion. Everything above it is laying on your skull. The parts of the nose below it cover your nasal cavity.
    - Retric 3y ago
      Anatomically correct skulls have an hole where the bottom of your nose is and the eyes are both smaller and higher up than you probably think. https://en.wikipedia.org/wiki/Orbit_(anatomy)#/media/File:Eye_orbit_anatomy_anterior2.jpg https://en.wikipedia.org/wiki/Orbit_(anatomy)#/media/File:Ey... Looking at yourself in a mirror, if you hold your finger over the top of your nose your eyes will see under your finger. Move your finger just low enough so you’re seeing over it and you should be touching the bottom of your nasal bone. At that point your nose should be more than a finger width froward from the bottom of your orbital socket which is where the hole in skulls starts in those skulls.
    - Calavar 3y ago
      Look at a picture of a skull in profile. You'll see that there is half a nose, not no nose. That half of the nose that you can see is the bony part. The missing half is the cartilaginous part. Why is there a hole? Because your nasal canal extends inside your skull to connect with the back of your throat. I guess I don't fully understand the question there.
Moto7451 3y ago
While you can’t hug them, see if your nearest aquarium has a touch tank experience. Usually they do those with rays/skates but you can also find them with Nurse sharks. Either way, you’ll literally get a feel for their composition. From memory it’s more like the stiff parts of your nose running near/along the bone and unlike your ears in any way.
darkerside 3y ago
My guess is that, yeah, if you empty them of water

gwerbret 3y ago

> we need a store of calcium to mediate blood pH Blood pH is regulated mainly by dissolved carbon dioxide and bicarbonate [1]. There's an order of magnitude less calcium in the blood, usually in the form of calcium phosphate, than either of those, and the amount is extremely tightly regulated within a very narrow concentration range -- far too narrow to have a notable effect on pH. [1]: https://www.ncbi.nlm.nih.gov/books/NBK482291 https://www.ncbi.nlm.nih.gov/books/NBK482291

DoreenMichele 3y ago
The majority of calcium ions within the cell are bound to intracellular proteins, leaving a minority freely dissociated. When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a cardiomyocyte during each cardiac cycle becomes bound to calcium buffers, creating a relatively small change in free calcium. https://en.m.wikipedia.org/wiki/Calcium_buffering https://en.m.wikipedia.org/wiki/Calcium_buffering I raised and homeschooled two kids and watched a lot of when dinosaurs ruled the earth type stuff. That's my source for the idea that a store of calcium was critical for allowing life to leave the ocean and I've tried repeatedly to search for additional info on this and can never find it. I have no problem imagining that calcium is essential for buffering pH in land mammals and that free calcium ions simultaneously are tightly regulated and not directly used to move that number for the blood in short time frames. That actually fits perfectly well with my mental models that cellular acidosis is a more fundamental problem that fuels acidosis of bodily fluids. If anyone has any good sources that might clarify this relationship for me, that would be cool.
- Retric 3y ago
  > calcium is essential for buffering pH Except that’s not what’s going on. The Wikipedia article lays it out. The amount of hydrogen ions someplace is what PH means, so controlling PH is controlling the number of hydrogen ions. The same thing happens with calcium, but rather than doing the buffering it’s the number of calcium ions being controlled. Calcium buffering is controlling the number of calcium ions. > Calcium buffering describes the processes which help stabilise the concentration of free calcium ions within cells, in a similar manner to how pH buffers maintain a stable concentration of hydrogen ions.[1] The majority of calcium ions within the cell are bound to intracellular proteins, leaving a minority freely dissociated.[2] When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a cardiomyocyte during each cardiac cycle becomes bound to calcium buffers, creating a relatively small change in free calcium.[2]

quickthrower2 3y ago

Thanks, that is fascinating. The amount of gold/silver is too. Even just the amount of salt. Measure in parts per 1000! I like having a wow moment about something we take for granted.

eru 3y ago

> Most land animals have a skeleton [...] Most land animals don't have a skeleton. Most land animals are insects and similar critters.

medstrom 3y ago
They have exoskeletons, which still serve the stated purposes.
- eru 3y ago
  Those exoskeletons are made of chitin. Chitin is a carbohydrate. It doesn't really have much to do with calcium.

thaumasiotes 3y ago

> Most land animals have a skeleton not just to provide physical scaffolding to hang tissue on but because we need a store of calcium to mediate blood pH, something sea life doesn't require thanks to those minerals in the water. That's why you can have sharks which are mostly supported by cartilage Well, the other reason sea life doesn't require rigid bones is that water provides a lot more buoyancy than air. Jellyfish work fine in the water; on land they're immobile puddles of glop.