A very interesting question GNobern and some excellent, insightful and informative replies as well. I think you really in all honesty get used to it very very quickly, what you have to understand and be aware of its not a sexual situation, you are their as a medical profession to try to alleviate, treat, comfort and support your patient. Most of the times your patient are ill in need of care whether its surgical or medical patient and you are their to provide the necessary care if that involves nudity or exposure so be it, its the care that is the over riding factor not the nudity or exposure. When you have to perform care and activities that require nudity you become so focus on ensure that they are performed gently, efficiently, correctly, aseptically, timely etc that the nudity never comes into your conscious thought at that time.
Like Marshie I grew up in a conservative household and so I was naturally concerned about how I would react to nudity as a Nurse ( I'm male by the way), my first placement was on a Male surgical ward, so I expect it was not as awkward as it could have been and so by my second placement a female medical I was fairly comfortable with nudity. I expect their is a bit of awkwardness when you first have to expose a female patient to perform care give the male female dynamic but that is soon forgotten in the greater scheme of things. As you have read some women do prefer an male care provider whether that be a Doctor or a Nurse and will ask for it.
On the flip side their are some female patients who do genuinely prefer a female Nurse ( in 25 years I have only met 2) and I have never taken it personally, I'm here to provide care, support and comfort and if they are more comfortable with a female care provider then so be it. I have had female patients who were not sure about a male nurse caring and performing intimate procedures on them (you can always tell from their non verbals), as long as you are caring, gentle, supportive and keep the exposure and nudity to a minimum they are soon comfortable and enjoy the male female banter. Of course you get the flip side to that where they can be a bit of an exhibitionist and enjoy a bit of sexual frisson and tension from the male female dynamic ( normally the slightly older female patients late 30's to early 40's).
I must admit also I was a bit nervous before I started on the Gynecology Wad as a student, even thought I was almost 18 months ( out of 36 months) into my student nurse training on how they would react to a male nurse. I will admit it was the most awkward I have every felt on a first shift the first day I started, but I had a very lovely link nurse ( mentor) and some great patients and by the end of that shift I had no issues with their nudity ( I being the only male nurse I think was such a novelty, I had lots of patient wanting me to nurse them and were very accommodating, friendly and supportive ). What was interesting was the husbands or partners reactions some were really supportive and I think like the idea of me caring for their wives or partners, as we could discuss " guy stuff , like football, cars etc" as I think it was very awkward for them during visiting times ( we had the older nightingale type wards - hospital ward, which contains one large room without subdivisions for patient occupancy) so another male to chat with was a relief. Yet others you could sense were not happy at a male nurse caring for their wives or partners but did not say or comment on it.
As for the gory aspects I was concerned about how I would react to the sight of "blood and guts" but I think when you are there in a professional capacity its totally different you sort of go into work mode for a better choice of words and deal with it as Susie said once that adrenaline "kicks into your system" the so call Adrenaline rush you just get on with what you have to do regardless on how gory it is .
I work In ITU ( the British equivalent of ICU) so have seen lots of Trauma which can be very gory so its not as shocking as its used to be as when you first start, I really love working in ITU and cant see myself in any other field of Nursing, been there for 21 years and still love it as I did like when I first started.
As other have said I find the most upsetting part of my job is dealing with the death and dying of a patient especially if its tragic ( like teenagers, or young mothers and fathers). Its the one part of the job you never get used too, you learnt how to cope with it better as you gain experience but never really get use to it. Its the same for Doctors as well, my senior Consultant on the unit always copes very badly, he's always very professional but you can tell its heartbreaking for him when he has to tell the families there is no more that can be done ( he is very very good at this even thought its breaks his heart every time he does it ).
On the upside their is no feeling like when you help a patient to recover from critical illness especially if they were not expected to survive, it really makes the job so rewarding and worthwhile.