A rete mirabile (Latin for "wonderful net") is a complex of arteries and veins lying very close to each other, found in a number of vertebrates, and serving different purposes.

In birds with webbed feet, a rete mirabile in the legs and feet transfers heat from the outgoing (hot) blood in the arteries to the incoming (cold) blood in the veins, with the net effect that the internal temperature of the feet is much closer to the ambient temperature, thus reducing heat loss. In this example the rete mirabile functions as a biological heat exchanger. A similar structure is seen in other vertebrate extremities, including the neck of the dog, in order to protect the brain when the body overheats, mammalian testes, which are more productive at lower temperatures, and fishes such as tuna, whose core temperature is higher than that of the cold deep waters they inhabit.

In some fish, a rete mirabile fills the swim bladder with oxygen, using a countercurrent exchange system where varying pH levels causes oxygen to unbind from blood hemoglobin and then come out of solution when the blood is supersaturated.

In giraffes, a rete mirabile in the neck equalizes blood pressure when the animal bends down to drink.

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 Vesalius to demonstrate the error.

External links

* Rete used in dolphin testes and womb
* a brief discussion
* Fish gas bladder workings
* a version with diagrams

Category:Animal anatomy