How could Obito transport his body parts in another dimension without bleeding? I have a question that's been bothering me for a while. I know that Naruto is supposed to be a manga written for teens and pre-teens so some stuff doesn't have any explanation or represents a plothole, but still I would really like to know whether this question has a reasonable answer or not. How can Obito transport his body parts in another dimension without the person that passes through him getting blood over his/her entire body? And why doesn't the body just collapse with the head being in another dimension?
Obito uses a technique called Kamui.


  Kamui is a powerful Mangekyō Sharingan dōjutsu that creates a unique and specialised form of space–time ninjutsu. It allows the user to achieve two very distinct, yet closely associated feats — teleportation and intangibility.


Intangibility, here refers to making the body or certain parts of body inaccessible to the physical world. Thus, no one could touch him and passed right thought Obito.