How to deal with students leaving the class for 10 min during the lecture?
The existing answers seem to me extreme.  I don't think some sort of draconian blanket "leaving-the-room policy" is needed here.  I would suggest the following:


For students leaving occasionally: Ignore it. They are adults and sometimes things in their lives may take higher priority than your class (e.g. going to the bathroom, feeling unwell, family emergencies, etc).  If it's distracting to you, well, deal with it.  It's a classroom, not a funeral, and you are a professional.  Take a breath and get back to teaching.
If you see a particular student leaving often: Have a private word with them to see if things are okay.  They may have special circumstances that you don't know about (chronic illness is one distinct possibility).  Once you know their situation, you may be able to offer specific suggestions that will reduce the disruption and/or get them more engaged in the class.  
If, after talking to them, you are convinced they are just walking out from spite, and they won't stop: Follow your institution's policy on disruptive students.  Your department chair should have further guidance.  It may ultimately be necessary to drop them from the class.


A short break in the middle of a 75-minute class is a reasonable idea, but I would keep it very short: perhaps 1-2 minutes, enough to stand up and stretch, not more.  It should not significantly reduce the amount of time students spend on task.  (Otherwise, as mentioned above, you may encounter problems with your institution's authorities that your class does not provide as much instructional time as promised by its number of credit hours.  Moreover, some students will see it as wasted time and resent it.)  Better yet, break up the lecture with some other sort of productive activity (small group discussions, problem solving, etc).  

I don't think it's appropriate to publicly shame students for poor etiquette, or shut them out of class if they leave.  You will unfairly punish students who legitimately need to step out for a few minutes, and anyone who is doing it from spite or boredom will just be further alienated.