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Sean Cate
Sean Cate
February 12, 2024 ·  3 min read

The “Seam” Running Along Your Scrotum is a Raphe, and This is Why You Have It

The human body is a complex and fascinating creation; even the most familiar parts can hold surprising secrets. One such mystery that has puzzled men for generations is the “stitch” running along the bottom of the penis, through the center of the testicles, and to the anus. This “stitch” is known as a raphe. The raphe has three anatomical sections: the penile raphe, scrotal raphe, and perineal raphe. For the sake of this article, we will simply refer to it as the raphe.

The raphe is a seam-like structure of thicker skin that starts at the base of the penis, extends through the center of the scrotum, and reaches down to the anus. It is a unique feature both males and females share, though its appearance and thickness can vary between individuals.1

Your Raphe Devlopes in the Womb

The origin of the raphe can be traced back to the early stages of human development in the womb. At around seven weeks after conception, male and female fetuses exhibit a remarkable similarity in their genital anatomy. They both possess a urogenital tubercle, urogenital swellings, and urogenital folds.

After this critical period, differentiation occurs. In male fetuses, the testicles begin to produce testosterone, leading to the development of the scrotum and the underside of the penis. The urogenital swellings swell and fuse in the middle, forming distinct male genital structures.

The line down the middle, called a ‘raphe’, is just a reminder of how all humans start out with a common female genital anatomy until 7 weeks after conception,” explains the Intersex Society of North America.

The Raphe: A.K.A. Your Scrotal Seam

The raphe is called the penile raphe when it appears on the shaft of the penis and the scrotal raphe when it is present on the scrotum. Females also possess a version of the raphe, extending from the anus to the labia majora, due to the development of their genitals in the womb at around the same time.

As with many biological structures, the raphe is subject to individual variation. Various factors can influence its appearance, resulting in differences such as being pearly, pigmented, prominent, or wide. These distinctions, however, are typically within the range of normal development and do not imply any health concerns.

Moreover, some individuals might experience intersex appearances due to unusual hormone levels during fetal development. In such cases, the genitals may not fit the typical male or female pattern, further highlighting the intricacy of human development.

From Labia to Scrotum: A Journey Unraveled

Now that we have shed light on the raphe’s origin and development, it’s time to explore how it is connected to a woman’s embryonic body and the fascinating process that transforms labia into the scrotum.

During the first seven weeks in the womb, human embryos are in a state of sexual indeterminacy.2 Both male and female embryos possess what is known as the “sexually indifferent gonadal ridge,” which contains the labio-scrotal folds.

The turning point in determining gender occurs when a specific gene called the “sex-determining region” on the Y chromosome is activated. This gene stimulates the production of cells that eventually lead to the formation of testosterone. Consequently, the presence of the Y chromosome sets the development of male characteristics in motion.

As the Y chromosome influences the production of testosterone, the labio-scrotal folds in male embryos undergo a remarkable transformation. They begin to develop and fuse, forming the scrotum, while the urogenital swellings grow to become the underside of the penis.


The raphe, that mysterious “stitch” running along the bottom of the scrotum, is a remnant of our shared human development in the womb. As we have explored, it serves as a reminder of how all individuals, regardless of gender, initially start with a common female genital anatomy. Thanks to the intricate interplay of hormones and genetic factors, we embark on a fascinating journey that shapes our distinct male or female characteristics.

So the next time you lads come across your scrotal seam, take a moment to appreciate the remarkable journey that brought you to this point. Embrace the complexity and beauty of human development, for it is a testament to the wonders of life.

Keep Reading: Medical student flees anatomy class after finding friend’s body on table


  1. What Is That “Seam” Running Along The Middle Of Your Ball Sack?IFL Science. James Felton. February 1, 2023.
  2. 5 things you didn’t know about the male body.” Shortlist. Danielle De Wolfe. February 19, 2014.