Some headcanons regarding TMNT physiology
Over the years, I have come up with some headcanons regarding how I believe the Ninja Turtles' bodies work. I thought that perhaps it might be nice to finally share them with all of you.
These don't apply to all the iterations, of course, but they are pretty well universal in my mind, and I tend to incorporate most of them into my fanfics.
The Turtles (like leatherback sea turtles, echidnas, and some dinosaurs) are mesotherms, meaning they are neither warm nor cold blooded. They are, instead, in a middle-ground: they internally generate heat, but not to a constant temperature. In the Turtles' case, they will shiver when cold, and their bodies will not shut down right away when the temperature dips too low, though they may lose some energy and find it hard to concentrate.
Unlike many other modern reptiles and amphibians, who have a three-chambered heart, the Turtles have four-chambered hearts (like mammals and dinosaurs) that are larger and stronger than average human hearts and located at the center of their chests.
While the average human blood capacity is around five liters, the Turtles have about seven. Much of the blood flows under the shell -- a remnant of their lives as ordinary turtles, whose own blood does so in order to warm them when they bask. This means that the Turtles could lose close to three liters of blood before dying, while a human would only be able to lose two.
Their blood is also highly efficient at clotting, but that also means that storing blood for transfusions is difficult, and so must be directly transfused from one turtle to another in emergency situations.
Owing to their extensive circulatory system, they also have a larger lung capacity than humans and more oxygen-rich blood, and so are able to hold their breath for extended periods of time without adverse effects. Other than this, the Turtles' respiratory system is very much like humans', utilizing a diaphragm to inflate and deflate their lungs.
Like regular turtles, they do not have ribs, but rather their carapaces and plastrons serve that purpose, and they have muscles under their shells that keep their internal organs right where they belong.
Also like regular turtles, their spines curve along the insides of their shells. A direct hit on the center of their shells, then, could cause damage to their spinal column and nervous system, but fortunately their vertebral shields offer a fair amount of protection, so it would take quite an impact.
The Turtles are highly resistant to most infections and diseases, which increases their immunological responses. They do not get sick easily, and they recover quickly.
While their scales are not apparent, they are integrated into their skin, making it tougher than human skin. It takes a very hard hit to raise a bruise, and it is difficult to cut through without a very sharp or pointed blade.
Their bones are similar to humans, but are more resistant to breaking. They also heal quicker and stronger if they are broken.
Their muscles are also very close to human-like, but they are stronger than an average human due to compensating for the extra weight they carry in their shells. Because of this, their ligaments and tendons are also tougher, and it is difficult for them to have a joint dislocated.
Their sense of smell is more acute than humans, but not to an extreme degree. They are also not as bothered by foul smells (though this has more to do with living in a sewer than their physiology).
Their eyes are a bit tougher and more resistant to damage than human eyes due to a protective membrane that covers them. They see a bit better than humans in dark places and underwater.
Their hearing is somewhat more attuned to lower frequencies than human hearing, and is not dependent on external ears but rater an internal auditory system (making direct damage to their hearing unlikely).
They are capable of being knocked unconscious, but it takes a significant impact. Permanent or lingering damage to their brains is unlikely due to their structure, and so they also do not tend to suffer the same side-effects that humans would in the same circumstances (nausea, memory loss, etc.).
Although their nutritional needs are similar to humans, they do not need to eat every day, and in fact can get by quite well without food for a week if necessary (though they won't enjoy it). When food is readily available, however, they will eat as much as possible to store up energy. Their metabolism does not slow down when they do not eat, so overexerting themselves when they haven't had any food for a while can burn them out suddenly.
Their sleep schedules are much like most diurnal animals, though they are able to stay awake for extended periods of time and can get by on little sleep, if necessary. There have been times when they have been awake for days on end, getting by on short one hour naps here and there. In general, though, they like to have a regular sleep/wake cycle.
Like other reptiles, the Turtles never stop growing throughout their lifetimes; however their growth is slow, topping off at about 1-2 inches every five years.
Does anyone have anything they would like to add to the list? I actually had fun compiling it!
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