# Why aren't our brains red? Perfusion, "suffusion"(?), and stuff gushing out **URL:** \ **Category:** Factual Questions\ **Created:** [July 9, 2016, 4:59pm UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484 "2016-07-09T16:59:55Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![KarlGrenze](https://avatars.discourse-cdn.com/v4/letter/k/dbc845/32.png) [@KarlGrenze](https://boards.straightdope.com/u/KarlGrenze)\ **Post date:** [July 11, 2016, 3:49pm UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/21 "2016-07-11T15:49:03Z")
> [@Leo\_Bloom](#): > > So let’s take bone, the bony part (:)), with the mineralization and calcium deposits. How much of the bone, on an ongoing basis, receives/needs O2? Does some part of it (the surface, maybe) amount to, physiologically, excreta, having got past the part where the rest of the organism has facilitated such mineralization/calcification? Eventually, all cells need O2 and other minerals and sugar, and need a way to get rid of their waste products (CO2 for example). 🙂 But yes, the metabolism of the osteocyte (the cell within the bone itself) is probably much lower than other organs (brain), but all of the bone needs to get O2 in order to function properly, otherwise bone dies. And yes, there are diseases and situations in which this happens. Microscopically, the bone is not completely solid (even the solid looking, cortical bone). It has canaliculi that connect the cells within with each other and with the exterior, and it is through this system that they get their oxygen and rid their waste products. The cells that produce bone are called osteoblasts, and they are outside. Metabolically, they’re more active than osteocytes, but they are also closer and nearer to the bone marrow and vessels that go into the bone. The surface of the bone, unlike the surface of the skin, is not “excreta”. All of it is living tissue, all of it needs oxygen (at various levels and needs), and without it the bone most certainly dies. Also, your bone is constantly being remodeled. At different rates throughout life, but the bone is not “static” like for example neurons or cardiac muscle. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [July 11, 2016, 4:58pm UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/22 "2016-07-11T16:58:18Z")
To put some numbers on that: Only 60 to 70% of living bone is the mineral component. [https://www.reference.com/science/composition-bone-e6cf7808d3229607](https://www.reference.com/science/composition-bone-e6cf7808d3229607) ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 11, 2016, 5:39pm UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/23 "2016-07-11T17:39:48Z")
Thanks to **Karl** and all the posters. What a fun thread, post-by-post fighting of ignorance. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [July 11, 2016, 5:51pm UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/24 "2016-07-11T17:51:00Z")
> [@KarlGrenze](#): > > …Microscopically, the bone is not completely solid (even the solid looking, cortical bone). It has canaliculi that connect the cells within with each other and with the exterior, and it is through this system that they get their oxygen and rid their waste products. The cells that produce bone are called osteoblasts, and they are outside. Metabolically, they’re more active than osteocytes, but they are also closer and nearer to the bone marrow and vessels that go into the bone… 1. What travels through these canalculi to carry out those function? 2. Are the “functional units” circulated, or are they one-way packages–from O2 pickup to O2 transfer, and then die, or change after that one transit? (As opposed to blood cells, which do eventually die, but do their stuff repeatedly for a while.) 3. Does the functioning of the above query (2) _even exist_ in the human body? Or am just making this shit up, and it’s a good thing I’m not God (one of many reasons, admittedly)? 4. Not a query: I never knew the word canalculi…it reminds me of the animalculi he found swimming around under his scope… ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [July 12, 2016, 9:40am UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/25 "2016-07-12T09:40:01Z")
> [@Leo\_Bloom](#): > > I _know_ that. It’s “raw head['s]” companion in words. Aah, I get it now > [@](#): > > And a propos, since the sentence mentions bloody bones, which both of us recognize as a striking juxtaposition. Goddamn but we’re cultured and witty. > > Right? Damn skippy. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [July 12, 2016, 9:51am UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/26 "2016-07-12T09:51:43Z")
> [@Leo\_Bloom](#): > > 1. What travels through these canalculi to carry out those function? Periosteocytic fluid, but I think you’ll find _most_ of the substance flow is osteocyte-to-osteocyte via gap junctions, after initial uptake from the bone capillaries/before excretion to those caplillaries. The fluid is for the larger molecules and ions like Ca and P and proteins. ---
**Author:** ![KarlGrenze](https://avatars.discourse-cdn.com/v4/letter/k/dbc845/32.png) [@KarlGrenze](https://boards.straightdope.com/u/KarlGrenze)\ **Post date:** [July 12, 2016, 10:03am UTC](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484/27 "2016-07-12T10:03:34Z")
> [@Leo\_Bloom](#): > > 1. What travels through these canalculi to carry out those function? > > 2. Are the “functional units” circulated, or are they one-way packages–from O2 pickup to O2 transfer, and then die, or change after that one transit? (As opposed to blood cells, which do eventually die, but do their stuff repeatedly for a while.) > > 3. Does the functioning of the above query (2) _even exist_ in the human body? Or am just making this shit up, and it’s a good thing I’m not God (one of many reasons, admittedly)? > > 4. Not a query: I never knew the word canalculi…it reminds me of the animalculi he found swimming around under his scope… No, the canaliculi in the bones are usually too small for complete cells, they mostly contain either fluid or cellular extensions (think like arms) as mentioned above. So nothing really dies during transfer, it is either going through diffusion or active cell to cell transfer. As mentioned, different cells have different metabolic rates and different needs, adapted to their environment. But they all, definitely, need some oxygen and some way to get rid of their waste. How much or how frequent may vary, but the need is there. [Previous page](https://boards.straightdope.com/t/why-arent-our-brains-red-perfusion-suffusion-and-stuff-gushing-out/759484.md?page=1)