Chapter 23 - Section 23.7 - Study Guide - Assess Your Learning Outcomes - Page 922: 4

The male urethra is a tube that serves as a conduit for the passage of both urine and semen. It runs through the penis and has three distinct segments: the prostatic urethra, the membranous urethra, and the spongy (penile) urethra. The male urethra also has an external urethral sphincter, which plays a role in urinary control. Here's an overview of the anatomy of the male urethra and its segments: **Three Segments of the Male Urethra**: 1. **Prostatic Urethra**: - The prostatic urethra is the most proximal segment and runs through the prostate gland. - It receives urine from the bladder and is also the portion of the urethra through which ejaculatory ducts from the seminal vesicles and vas deferens empty into the urethra, contributing to the composition of semen. 2. **Membranous Urethra**: - The membranous urethra is a short segment that passes through the urogenital diaphragm, a muscular structure that separates the pelvis from the perineum. - It is surrounded by the external urethral sphincter, a skeletal muscle that provides voluntary control over urination. 3. **Spongy (Penile) Urethra**: - The spongy urethra is the longest segment and runs through the length of the penis. - It passes through the corpus spongiosum, a column of erectile tissue that surrounds the urethra and expands during an erection. **External Urethral Sphincter in Males**: The external urethral sphincter in males is a voluntary skeletal muscle that surrounds the membranous urethra as it passes through the urogenital diaphragm. This sphincter plays a crucial role in urinary control, allowing voluntary initiation and inhibition of urination. 1. **Location and Structure**: - The external urethral sphincter surrounds the membranous urethra as it passes through the urogenital diaphragm in the perineum. - Like in females, the external urethral sphincter in males is composed of skeletal muscle fibers under conscious control. 2. **Function**: - The external urethral sphincter contracts to maintain closure of the urethra, preventing the involuntary release of urine. - During urination, voluntary relaxation of the external urethral sphincter allows urine to flow out of the urethra. 3. **Innervation**: - The external urethral sphincter is innervated by somatic motor nerves from the pudendal nerve, arising from the sacral spinal cord. - This innervation allows for conscious control over the contraction and relaxation of the muscle. In summary, the male urethra has three segments—prostatic, membranous, and spongy—and is responsible for the passage of urine and semen. The external urethral sphincter provides voluntary control over urinary continence, allowing men to regulate urination.

The male urethra is a tube that serves as a conduit for the passage of both urine and semen. It runs through the penis and has three distinct segments: the prostatic urethra, the membranous urethra, and the spongy (penile) urethra. The male urethra also has an external urethral sphincter, which plays a role in urinary control. Here's an overview of the anatomy of the male urethra and its segments: **Three Segments of the Male Urethra**: 1. **Prostatic Urethra**: - The prostatic urethra is the most proximal segment and runs through the prostate gland. - It receives urine from the bladder and is also the portion of the urethra through which ejaculatory ducts from the seminal vesicles and vas deferens empty into the urethra, contributing to the composition of semen. 2. **Membranous Urethra**: - The membranous urethra is a short segment that passes through the urogenital diaphragm, a muscular structure that separates the pelvis from the perineum. - It is surrounded by the external urethral sphincter, a skeletal muscle that provides voluntary control over urination. 3. **Spongy (Penile) Urethra**: - The spongy urethra is the longest segment and runs through the length of the penis. - It passes through the corpus spongiosum, a column of erectile tissue that surrounds the urethra and expands during an erection. **External Urethral Sphincter in Males**: The external urethral sphincter in males is a voluntary skeletal muscle that surrounds the membranous urethra as it passes through the urogenital diaphragm. This sphincter plays a crucial role in urinary control, allowing voluntary initiation and inhibition of urination. 1. **Location and Structure**: - The external urethral sphincter surrounds the membranous urethra as it passes through the urogenital diaphragm in the perineum. - Like in females, the external urethral sphincter in males is composed of skeletal muscle fibers under conscious control. 2. **Function**: - The external urethral sphincter contracts to maintain closure of the urethra, preventing the involuntary release of urine. - During urination, voluntary relaxation of the external urethral sphincter allows urine to flow out of the urethra. 3. **Innervation**: - The external urethral sphincter is innervated by somatic motor nerves from the pudendal nerve, arising from the sacral spinal cord. - This innervation allows for conscious control over the contraction and relaxation of the muscle. In summary, the male urethra has three segments—prostatic, membranous, and spongy—and is responsible for the passage of urine and semen. The external urethral sphincter provides voluntary control over urinary continence, allowing men to regulate urination.