The term urethral sphincter refers to one of two muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s used to control the exit of urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

 in the urinary bladder

Urinary bladder

The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...

 through the urethra

Urethra

In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...

. The two muscles are the external urethral sphincter and the internal urethral sphincter. When either of these muscles contract, the urethra

Urethra

In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...

 is sealed shut.

The external urethral sphincter originates at the ischiopubic ramus

Ischiopubic ramus

The ischiopubic ramus is a compound structure consisting of the following two structures:* from the pubis, the inferior pubic ramus* from the ischium, the inferior ramus of the ischiumIt serves as part of the origin for the Obturator internus muscle....

 and inserts into the intermeshing muscle fibers from the other side.