Sphincter urethrae

Sphincter urethrae is a muscle that controls the flow of urine from the urinary bladder. It is part of the urinary system and plays a crucial role in urinary continence.

Anatomy

The sphincter urethrae, also known as the urethral sphincter, is a circular muscle that surrounds the urethra. It is located at the neck of the urinary bladder, where the bladder connects to the urethra. The muscle is composed of two parts: the internal sphincter and the external sphincter.

The internal sphincter is a smooth muscle that is involuntary, meaning it cannot be consciously controlled. It is responsible for maintaining urinary continence when the bladder is filling with urine.

The external sphincter is a striated muscle that is voluntary, meaning it can be consciously controlled. It is responsible for controlling the release of urine during urination.

Function

The primary function of the sphincter urethrae is to control the flow of urine from the bladder into the urethra. When the bladder is filling with urine, the internal sphincter is contracted to prevent urine from leaking into the urethra. During urination, the external sphincter is relaxed to allow urine to flow from the bladder into the urethra and out of the body.

The sphincter urethrae also plays a role in sexual function. In males, it contracts during ejaculation to prevent semen from entering the bladder.

Clinical significance

Disorders of the sphincter urethrae can lead to urinary incontinence, a condition characterized by the involuntary loss of urine. This can be caused by damage to the sphincter muscles, nerve damage, or conditions that affect muscle control, such as Parkinson's disease or multiple sclerosis.

Treatment for disorders of the sphincter urethrae may include medication, pelvic floor exercises, or surgery. In some cases, a device called a urinary catheter may be used to drain urine from the bladder.