Why does a male dogs pines swell and get stuck in a female when mating?

During mating, a male dog's penis swells due to the engorgement of blood, a process known as "tie." This swelling occurs as the male's bulbus glandis, located at the base of the penis, inflates to ensure a secure connection with the female. This tie can last from several minutes to over half an hour, allowing for successful mating and increasing the likelihood of fertilization. It is a natural part of canine reproduction.