A tractor unit pulling a semi-trailer. A truck pulling a semi-trailer using a trailer dolly. A semi-trailer is a trailer without a front axle. A large proportion of a semitrailer's weight is supported by a tractor unit, a detachable front axle assembly known as a dolly, or the tail of another trailer. A semi-trailer is normally equipped with landing gear (legs which can be lowered) to support it when it is uncoupled.
Bleeding, redness, and painful or sore gums can be a symptom of gingivitis (inflammation of the gums) that arises due to a number of different causes. Bleeding of the gums is sometimes referred to as gingival bleeding, and it may occur during brushing or flossing. The soreness can be accompanied by swelling of the gum tissues. Most commonly, gingivitis is the result of plaque buildup on the teeth around the gum line.
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.