A port is a harbor viewed esp. with reference to its commercial activities and facilities: a thriving port. haven is a literary word meaning refuge, although occasionally referring to a natural harbor that can be utilized by ships as a place of safety: to seek a haven in a storm. See also cherish.
The reason why bleeding gums is a big deal is because the bad bugs now have access to the whole body via the bloodstream. Yes, unfortunately, these disease causing microorganisms can and do swim into the bloodstream to access the rest of the body.
Puberty. The surge in production of the female hormones estrogen and progesterone that occurs during puberty can increase the blood flow to the gums and change the way gum tissue reacts to irritants in plaque, causing the gum tissue to become red, tender, swollen, and more likely to bleed during brushing and flossing.