Anterior urethra and posterior urethra

Urination is an indispensable behavior in people's daily life. It is an important part of metabolism and can excrete excess water and metabolic products out of the human body. Urinary discharge is through the urethra, and the urethra can be divided into the anterior urethra and the posterior urethra. There are some differences between them. The following will introduce in detail the differences between the anterior urethra and the posterior urethra.

The anterior urethra starts from the urethral opening and ends at the bulb. It is about 15 cm long and is covered with the corpus spongiosum of the urethra. It is attached to the two shallow grooves of the corpus spongiosum of the penis. This section of urethra is mobile and therefore not easily injured. The two ends of the anterior urethra are enlarged, one is located at the urethral opening, called the navicular fossa, and the other is located at the bulbar urethra.

The posterior urethra starts from the membranous urethra and ends at the bladder neck, and is about 4 cm long. The membranous urethra is the shortest, only about 1 cm, and is located between the two layers of triangular ligaments. It is surrounded by striated muscle, namely the external sphincter, and is the most fixed and weakest section. Improper use of urethral instruments can easily lead to injury, and the perineum is also the most vulnerable part when it is violently squeezed. The urethral prostate is about 3 cm long, starting from the triangular ligament, passing through the entire gland to the bladder neck. It is the widest part of the entire urethra. In the center of the posterior wall of this section of urethra, there is a bulge called the urethral ridge or the seminal vestibule, and there is a recess in the middle of it. There are openings of the ejaculatory ducts on both sides of the crypt, and the prostatic ductules open in the grooves on both sides of the seminal colliculus.

The prostatic part is the portion of the urethra that passes through the prostate. The lumen is the widest and is about 2.5 cm long. There is a longitudinal protrusion on the posterior wall, called the urethral ridge, and the protruding part in the middle of the ridge is called the seminal colliculus. There is a small depression in the center of the seminal colliculus, called the prostatic cyst. There is a pair of tiny ejaculatory duct openings on both sides, and there are many openings of the prostate excretory ducts on the urethral mucosa near the spermatophore; the membranous part is the part of the urethra that passes through the urogenital diaphragm, surrounded by the membranous urethral sphincter, with a narrow lumen. It is the shortest of the three parts, about 1.2 cm long; the spongy part is the part of the urethra that passes through the corpus spongiosum. The urethra is widest inside the bulbourethral part, called the bulbourethral part, where the bulbourethral gland opens. The urethra at the glans penis widens into the fossa navicularis. There are many mucous glands in the submucosa of the urethra, called urethral glands, whose excretory ducts open into the mucosa.