#physiology

"Arterialised blood returning from the gills of the tadpole by the anterior bronchial veins." Outlines of comparative anatomy. 1841.

The intricacies of fetal (right) and placental (left) circulation. The physiology of the circulation in plants, in the lower animals, and in man. 1873.

Yes, bones do secrete hormones, including osteocalcin, which plays a role in the fight or flight response. When the brain detects danger, it signals the skeleton to release osteocalcin, which helps to activate the sympathetic nervous system and suppress the parasympathetic nervous system, enabling the body to respond to the stress. 

Fantaisie Physiologique, František Kupka's illustration for his book Tvoření v umění výtvarném (Creation in the Plastic Arts), 1923

First, I know that M doesn’t smoke because of an addiction, but is it possible as a vampire to be addicted to any sort of substance that humans can become addicted to? Would harder drugs have any effect on their bodies?

Also, do the vampires have to drink water? and if so do they use the bathroom?

I suppose like alcohol, they wouldn't really feel the effect of drugs, so it's not something they'd become addicted to.

They have the ability to become addicted to things, because there are a lot of vampires addicted to blood, especially certain types. The MC's mutation in their blood is definitely addictive for them!

They don't drink water or go to the bathroom. They absorb everything from whatever they consume because of how intense their abilities are.

That's not scientific, but hey, magic! Lol! :D

" Okay, run away, I will look for another one

Even if it doesn't warm me anymore, I'll get over it "

— Valentin Strykalo

Flow of lymph. Circulation of blood. 1926.