rete mirabile

Discussions on introductory science topics. Ask simple or beginner questions and expect clear and level answers.

rete mirabile

Postby vivian maxine on March 23rd, 2017, 8:30 am 

I am finding contradictions on the internet searches. Is there, or is there not, a rete mirabile at the base of the brain? Perhaps a venous rete mirabile that cools the brain when the body is overheated? Thank you.
vivian maxine
Resident Member
 
Posts: 2837
Joined: 01 Aug 2014


Re: rete mirabile

Postby Faradave on March 23rd, 2017, 10:56 am 

Hi Viv,

Not in my (human) anatomy books, nor my memory. Humans do employ countercurrent exchange (close approximation of a network of small veins and arteries) to conserve heat (fingers and toes) and to conserve certain dissolved materials (in the kidneys). I believe this particular structure is more common in birds and fishes which endure harsher climates than we do. Only a few mammals have one.

"The ancient physician Galen mistakenly thought that humans also have a rete mirabile in the neck, apparently based on dissection of sheep and misidentifying the results with the human carotid sinus, and ascribed important properties to it; it fell to Berengario da Carpi first, and then to Vesalius to demonstrate the error."
User avatar
Faradave
Active Member
 
Posts: 1615
Joined: 10 Oct 2012
Location: Times Square (T2)
doogles liked this post


Re: rete mirabile

Postby vivian maxine on March 23rd, 2017, 11:43 am 

Faradave » March 23rd, 2017, 9:56 am wrote:Hi Viv,

Not in my (human) anatomy books, nor my memory. Humans do employ countercurrent exchange (close approximation of a network of small veins and arteries) to conserve heat (fingers and toes) and to conserve certain dissolved materials (in the kidneys). I believe this particular structure is more common in birds and fishes which endure harsher climates than we do. Only a few mammals have one.

"The ancient physician Galen mistakenly thought that humans also have a rete mirabile in the neck, apparently based on dissection of sheep and misidentifying the results with the human carotid sinus, and ascribed important properties to it; it fell to Berengario da Carpi first, and then to Vesalius to demonstrate the error."


This I was also getting, that it was mostly in the extremities of animals, including mammals - in legs, wings, fins. But when I got to humans, I began to get contradictions: firm statements that there was no such thing at the base of a human brain and that there was. One article said it kept the brain cool when the body was overheated to point of perspiration, etc. Like after hard exercise. Then there were a couple of places where it said they find an occasional human with a rete mirabile at the base of the brain, stressing that this is rare and that those people seem to have no problem with it.

It does make sense that there would be one there as we certainly want the brain kept cool. And the same thing might apply in reverse at bitterly cold climates. If there is no exchange protecting the brain, maybe that's why people who are freezing to death seem to get comfortable at the end. The brain is maybe shutting down and they drift into sleep before death? Then there is the fact that people need to bundle up with all the clothing they can find and put on ear muffs but go bareheaded and not seem to feel it.

Ah well, I'm just thinking. It looks like the majority is for no such thing in that particular spot. Thank you.
vivian maxine
Resident Member
 
Posts: 2837
Joined: 01 Aug 2014


Re: Not as brainy as we think.

Postby Faradave on March 23rd, 2017, 12:28 pm 

Drawings can't do justice to the actual vascularity of the human brain. In fact, 80% of the cranial cavity is occupied by blood vessels. This is seen by infusing a cadaver brain with colored latex, then dissolving away the nerve and glial (support cell) structure.

Brain Vessels Drawn.png
Drawing


Brain Vessels Cast.png
Vascular Cast

So, the body's core temperature is rapidly communicated to the brain, which in turn makes use of the entire skin, respiratory and metabolic apparatus to regulate its temperature.
User avatar
Faradave
Active Member
 
Posts: 1615
Joined: 10 Oct 2012
Location: Times Square (T2)
doogles liked this post


Re: rete mirabile

Postby vivian maxine on March 23rd, 2017, 12:58 pm 

Wow! Thanks. I like those drawings. Where did you find them?

Just asking this: Doesn't the brain itself have to read the temperature?
vivian maxine
Resident Member
 
Posts: 2837
Joined: 01 Aug 2014


Re: Seek, and ye shall find.

Postby Faradave on March 23rd, 2017, 2:12 pm 

I searched "cerebral vasculature" and chose "images from the results. The internet is a pretty amazing resource. I am having some trouble putting image links in to these posts lately. So, I often save an image to my computer, then upload it to SPCF in full edit mode.

Temperature sensors throughout the body report to the brain, but some reflex reactions, such as pulling your finger from a flame, may only require a shorter trip to the spinal cord and back to local (finger & arm) muscles.
User avatar
Faradave
Active Member
 
Posts: 1615
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: Seek, and ye shall find.

Postby vivian maxine on March 23rd, 2017, 2:29 pm 

Faradave » March 23rd, 2017, 1:12 pm wrote:I searched "cerebral vasculature" and chose "images from the results. The internet is a pretty amazing resource. I am having some trouble putting image links in to these posts lately. So, I often save an image to my computer, then upload it to SPCF in full edit mode.

Temperature sensors throughout the body report to the brain, but some reflex reactions, such as pulling your finger from a flame, may only require a shorter trip to the spinal cord and back to local (finger & arm) muscles.


Cerebral vasculature! I would never have thought of that. Neat anyway. Takes talent to do such. Thanks again.
vivian maxine
Resident Member
 
Posts: 2837
Joined: 01 Aug 2014


Re: rete mirabile

Postby doogles on March 24th, 2017, 12:57 am 

Interesting subject vivian maxine. I always like Faradave's responses.

I know you've covered the topic of the rete mirabile in the extremities of animals, but as a specific example of its usefulness, I think it was the main reason that huskies were useful for work in snow. They apparently never get frostbite of the extremities.

Just touching on the subject of the base of the brain - there is a 'reticular formation' at the base of the brain consisting of loosely connected neurons amongst white matter. The word 'reticular' means little net. It has nothing to do with vascularity of course - but I mention it just in case there were crossovers in your original reading material.
doogles
Member
 
Posts: 864
Joined: 11 Apr 2009


Re: More Food for Thought

Postby Faradave on March 24th, 2017, 1:19 am 

Thanks, doogles.

That will give us something to think about while we're practicing our planks. Not that we'll have nearly as much time doing that as you!
User avatar
Faradave
Active Member
 
Posts: 1615
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: rete mirabile

Postby vivian maxine on March 24th, 2017, 6:46 am 

Yes, thank you, doogles. I always enjoy both your replies. There is always something to learn in them.

that is interesting about huskies and their paws. Besides the rete (vascularity?), perhaps they have very thick, extra-protective pads as well as thick fur that overlaps. I'm not sure about the fur - never having seen a husky up close enough to notice - but I do know there are some breeds of cats with fur like that. Very thick between their toes and long. They have the same kind of hair growth at the ends of their ears. Fur keeps them warm, too.

I have a vague memory of something about that reticular formulation at the base of the brain. I'd probably never find it now as I went through so many articles when I began to see the contradictions. It brought me down a notch or two to read that Galen was wrong about something. Galen was a shining star in the field of medicine. We all have to be wrong about something. I shall try to find more about the reticular formulation. Thanks again.
vivian maxine
Resident Member
 
Posts: 2837
Joined: 01 Aug 2014
RoccoR liked this post



Return to Beginner Science

Who is online

Users browsing this forum: No registered users and 3 guests