How does this work?
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[Hemo the Magnificent](https://youtu.be/08QDu2pGtkc)
1960’s science movie made by Disney. Probably out of date, but it’s a trip to watch. You’ll recognize the voice of one of the actors in the opening scene.
Osmosis. So the reason skin infections can be hard ti treat is because the skin doesn’t have direct blood supply. Capillaries run throughout the skin and are surrounded by interstitial fluid. This fluid picks up things it’s low in such as oxygen and that’s then taken up by the cells. Sane in reverse for co2 but other waste products remain in the fluid, this fluid is moved around the body and replenished by the lymphatic system, similar to capillaries and blood vessels but instead of being pumped by the heart, your bodies skeletal movements work to pump it around. That’s why lower mobility = increased swelling, especially of lower limbs. The fluid is transported the lymph nodes around the body to be cleaned up. You can get cancer in a lymph node and unfortunately it’s often bad news, the lymphatic system will often spread the cancer around your body making it super hard to treat.
Edit to add; as peeps have pointed out, the oxygen and co2 exchange is diffusion not osmosis 🙂 my senior school biology teacher would be laughing at me rn lol
Some things like glucose and oxygen, but also certain hormones and minerals are transported through cells to their destination. Blood will bring those to their destination, endothelial cells will take it up and give it onto the next cell bordering them from behind, who then repeats the process.
Good question.
Thing is, nutrients, oxygen and waste could diffuse through several cells (i think it’s somewhere between several micrometers to millimeters) so we don’t need the capillaries to individually touch every single cell
Blood does need to get to every cell. However molecules that blood carry do. The oxygen is released from the blood cells when the cells get into tissue capillaries. The oxygen can diffuse across the cells that line the capillary and deliver it to cells beyond the blood vessels
This is something that always confused me; I was in my 40s before I had an understanding I was happy with. My understanding of biology isn’t very good, so you can get better details from the other answers. But my simple version may help with the basics.
One thing to remember is that cells vary a lot in size. The cells that form the capillary walls are much, much smaller than most other cells. That may help your mental imagery.
Another thing to remember is that there’s fluid that’s outside and between your cells. Your blood’s plasma is one example; there’s cells flowing in it, but it’s mostly just a fluid. Most parts of the body (like muscles) have cells that are more connected, but there’s still gaps with fluid in them. You can think of it kinda like wet sand; the sand takes up the bulk, but there’s plenty of water in there too, in the gaps between sand crystals.
As many others have said, blood cells don’t need to touch other cells to transfer their cargo. If blood cells are carrying lots of oxygen and there’s not much oxygen in the fluid nearby, then they release oxygen into the fluid. Similarly, if there’s lots of carbon dioxide in the nearby fluid and the blood cell doesn’t have much, then it’ll absorb some.
Many capillaries are porous; they have tiny holes between the cells that are large enough to allow small molecules, like oxygen, to pass.
For large molecules that need to be transported, they do a complicated dance where they get taken into the capillary cells and transported through it. (Molecules that do this have special structures or attachments to tell the capillary to move it through.) This also happens for anything in the brain (which has extra protection), and for anything that needs more complicated handling than simple diffusion (such as ions).
I hope this helps!
Weird vague answers here. Capillary walls have gaps that allow fluid containing glucose and electrolytes to filter from the blood, through these gaps, and wash over cells. The cells take in the glucose and electrolytes by osmosis.
The used up fluid is then drained by a system of ducts called lymphatics which collects it all and recycles it back into the blood stream through the two big boy ducts – 1) the thoracic duct and 2) the right lymphatic duct which pour it back into the jugular veins, hence the term “jug”-ular vein (that part’s not true, but it should be).
Blood does not technically reach very cell red blood cells are mearly vessels for oxygen which is then “absorbed” by the area that it is flowing through due to the fact tens of millions of cells die and are made in the body it is not necessary for “blood to reach the cells” hence cells dying and new ones replacing them
There are a lot of capillaries though. everything is with 2 cells away. The exception is your eyes
Your corneas aren’t blood-fed. They couldn’t be transparent otherwise. The nutrients diffuse through whatever fluids they’re soluble in. Blood just makes this easier. Its not strictly required. Its just an efficient circulation mechanism.
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