How long would you know how to survive short these organ systems?

All systems in the body are important and anyone of them failing would (probably) result in passing within a few hours. But which one of them is the most important? (Immediate death upon failure) And which one can you do minus for a few hours? Any information would be good, this is for a school project.

So, how long would you survive without your:
Circulatory system
Digestive System
Immune System
Reproductive System
Endocrine System
Musular and Skeletal System
Lymphatic
Urinary
Respiratory

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Answers:

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Circulatory system - direct death
Digestive System - couple weeks at best, depends on amount of body fat
Immune System - couple days at best, it depends which opportunistic infection gains the most ground
Reproductive System - this would not raison d`¨ºtre death
Endocrine System - hard to say.
Musular and Skeletal System - - on the spot death, loss of the diaphragm muscles would cease respiration
Lymphatic - couple days at best
Urinary - within hours
Respiratory - on the spot death

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