In a bicycle wreck, hard objects in or on a bike jersey can make the accident even more dangerous.  Please consider stashing things like keys, cell phone, inhaler, bike tools, and even flashing lights on the bike, e.g. in a bento box or tool bag, as opposed to in your jersey. 
 
Residing close to your jeresey pockets are:
Bones: ribs, hips, spine ... yikes!  Impact can cause fracture or contusion. 
Vital Organs: on the LEFT your kidney and spleen & on the RIGHT your kidney and liver.  Impact an cause internal bleeding. 
Muscles: a rider could receive significant blows causing bruising or hematomas. 

From Sophia Lal: concerned cyclist, local doctor and club member.