The Male Genital System

Education Gaps

Clinicians should be able to recognize common disorders of the male external genitalia, differentiate urgent from more benign conditions, perform initial diagnostic studies when indicated, treat appropriately, and refer to a specialist when necessary.

Objectives

After completing this article, readers should be able to:

1. Understand basic embryologic events in development of the male external genitalia.

2. Diagnose hypospadias and recognize associated disorders.

3. Differentiate micropenis, buried penis, and webbed penis.

4. Differentiate physiologic phimosis from pathologic phimosis and treat accordingly.

5. Recognize penile trauma.

6. Identify and manage cryptorchidism.

7. Establish a differential diagnosis of acute scrotal pain and treat accordingly.

Embryology

Male genital differentiation begins with the Y chromosome. During normal development, the sex-determining region Y chromosome (SRY gene) codes the bipotent gonad to undergo a male phenotype. (1) The origins of the testis can be traced back to the 5th week of gestation with formation of the gonadal ridge, an area where primordial germ cells migrate before differentiating. (1) The testicle is composed of both Leydig and Sertoli cells. The SRY gene helps drive differentiation of Sertoli cells that produce Mullerian inhibiting substance, also known as anti-Mullerian hormone, which prevents female pattern development. The Leydig cells, when stimulated by placental gonadotropin, also known as human chorionic gonadotropin, will produce testosterone. Primordial germ cells destined to become male gametes remain quiescent until puberty, when seminiferous tubules mature. (2) Movement of the testis in the retroperitoneum is regulated by insulinlike hormone and androgens during the transabdominal migration phase, occurring at 10 to 15 weeks, and during the transinguinal phases of descent, occurring at 25 to 35 weeks. (3) During this process, a sliver of peritoneum enters the scrotum, …