Final answer:
The ridge-like seam along the midline of the scrotum is known as the scrotal raphae, which correlates with the underlying scrotal septum formed by the dartos muscle.
Step-by-step explanation:
The ridge-like seam along the midline of the scrotum is called the scrotal raphae. The scrotum is a pivotal part of the male reproductive system, functioning as a pouch-like structure that houses the testes, epididymes, and part of the vas deferens. An important feature of the scrotum's anatomy is the dartos muscle, which is a layer of subcutaneous muscle that extends internally to form the scrotal septum, thus creating two compartments, each containing one testis. The appearance of the scrotal raphae is a visible landmark and is essentially an external manifestation of the scrotal septum.