A newly discovered body part changes our understanding of the brain (2016)
<i>Thus, the system not only allows for recirculation of bodily fluid, but it also provides a means for the immune system to sift through material from around the body in order to scan for infection. Without lymphatics, fluid would build up in body tissues, and there would be no way to alert the adaptive immune system to invading pathogens.</i><p>Something medical texts tend to not spell out:<p><i>Lymph</i> is more or less blood, minus certain blood parts (like red blood cells). And when it gets into the tissues it gets called <i>interstitial fluid</i>.<p>This is all the same fluid circulating through the body, with different elements added or removed in different contexts. It&#x27;s really quite elegant and you can think of it sort of like the water cycle. (<a href="https:&#x2F;&#x2F;water.usgs.gov&#x2F;edu&#x2F;watercycle-kids-adv.html" rel="nofollow">https:&#x2F;&#x2F;water.usgs.gov&#x2F;edu&#x2F;watercycle-kids-adv.html</a>)<p>Interstitial fluid would be sort of like groundwater. And like groundwater, it gets into the tissues via seepage.<p>The circulatory system would be kind of like rivers and streams.<p>So part of this fluid cycle is controlled by the pump action of the heart. When it is in your blood vessels (and I think also when it is in the lymphatic system), the heart pumps it, driving the circulation.<p>When it is out in the tissues, it is beyond the reach of the heart. And this is where things get really fascinating.<p>It is driven back to the circulatory system via two different methods, depending on where it is. The brain has a separate system from the rest of the body.<p>In the brain, the glymphatic system flushes fluids from the tissues <i>while you sleep.</i> This is a primary function of sleep and flushing these fluids out is how the body &quot;takes out the trash,&quot; which is likely why sleep deprivation is increasingly shown as associated with both the build-up of certain proteins in the brain and, ultimately, certain brain disorders.<p>In other tissues, muscle action drives the fluid back to the circulatory system. (Remember, the heart is just a big muscle. So this makes perfect sense.) So exercise dramatically increases the rate at which interstitial fluid gets returned to the circulatory system.<p>This means that one of the functions of exercise is &quot;taking out the trash.&quot; And this is likely a huge and overlooked factor in why exercise is so beneficial to your health.<p>Different sources cite different rates, but exercise may increase the outflow by as much as eight times the normal speed of outflow via seepage. It&#x27;s really a big difference.<p>If you have any health issues, understanding this human internal &quot;water cycle&quot; is something I highly recommend as enormously helpful. I sometimes take a walk to help myself feel better and I know that at least part of why that sometimes helps is it clears waste products from my tissues by pumping up the volume -- literally -- on the body taking out the trash.<p>I think that&#x27;s everything I wanted to say.