Gallifreyan physiology

Little is known about Gallifreyan physiology except in regards to specific members of Gallifreyan society, namely the class known as the Time Lords, more specifically the Time Lord known as the Doctor. Consequently, the following articles may have some inaccuracies due to these biases.

External anatomy
Externally, Gallifreyans are identical to Humans, however, whereas the Humans of Earth have a diverse range of ethnicities, Gallifreyans tends towards to have a mostly Eurasian appearance.

Resiliance
The Doctor was generally tough and resiliant, being able to survive extreme cold (DW: The Seeds of Doom) and extreme heat (DW: The End of the World). He could survive the subzero temperatures of vacuum for around 6 minutes. (DW: Four to Doomsday) as well electric shocks that would be fatal to Humans (DW: World War Three).

Body temperature
The Doctor had a mean body temperature of 60 degrees on the Earth Fahrenheit scale (16 degrees Celsius) (DW: Spearhead from Space)

The Brain
The Time Lord brain was much more complex than that of Humans as well as larger. This size differences means brain transplants into a Human body would have been impossible. (DW: The Brain of Morbius)

They are telepathically linked to one another and are even capable of joining the entire Time Lord intelligence as one. (DW: The Invisible Enemy) In times of psychic or physiological stress, Time Lords may even enter a self-induced coma. Time Lords can also separate the hemispheres of their brain, allowing them to multitask easily. (PDA: Island of Death)

Dual cardiovascular system
Natural born Gallifreyans born before the time of Rassilon and Pythia had two hearts. (NA: Cat's Cradle: Time's Crucible, Lungbarrow) Loom-born Gallifreyans (be they Time Lord or not) born after Pythia's curse of sterility, are loomed/born with a single heart and gain their second heart after their first regeneration. (MA: The Man in the Velvet Mask), "one for casual, one for best" as Romana once joked. (source?) Time Lords can survive with only one heart, should the other be punctured or destroyed, though they will be weakened greatly. (MA: Managra)



Romana could stop her hearts at will and feign death. (DW: Destiny of the Daleks) They only have a resting heart-beat of 10. (DW: Spearhead from Space)

Repiratory system
In order to use these two hearts, the Time Lords require advanced respiratory system. Instead of large lungs, they have a series of pulmonary tubes parallel to the lymphatic system. This makes them positively buoyant, which allows them to swim with ease. (PDA: Island of Death) This also means they can place themselves in a trance state which reduces the need for oxygen. (DW: Terror of the Zygons, Four to Doomsday)

Gallifreyan have a respiratory bypass system, which allows them to survive strangulation. (DW: Pyramids of Mars).

Circulatory system
Gallifreyan blood is different in composition then a Human's. It doesn't have the same A and B types. (DW: The Invisible Enemy, Spearhead from Space)

Other facts

 * Gallifreyans are susceptible to the intoxicating effects of alcohol. Time Lords can easily shrug off the effects when they must. (PDA: The Quantum Archangel, DW: The Girl in the Fireplace)


 * In the latter case, the Time Lord in question, the Doctor may only have feigned drunkenness.

The Doctor was susceptible to certain toxic gases and sleep-inducing drug, though not more so than a Human in the same position. (DW: The Brain of Morbius). The Doctor had an allergy to gases in the praxis range of the spectrum. (DW: The Caves of Androzani)

However, unlike Humans, the Doctor was immune to the voice-altering effects of helium. (DW: The Robots of Death)