Human Anatomy and Physiology - N. I. Fedyukovich 2003

Internal Organs
Urogenital System
Urethra

The Urethra (urethra) is designed for the periodic elimination of urine from the Urinary Bladder and the ejaculation of semen (in males).

The male urethra is a soft, elastic tube 16—20 cm in length. It originates at the internal urethral orifice of the urinary bladder and extends to the external urethral orifice, which is located on the glans Penis.

The male urethra is divided into three parts: the prostatic, membranous, and spongy parts. The prostatic part lies within the prostate and is about 3 cm long. On its posterior wall, There is a longitudinal ridge—the urethral crest. The most prominent part of this crest is called the seminal colliculus or verumontanum, at the apex of which is a small depression—the prostatic utricle. On either side of the prostatic utricle, the openings of the ejaculatory ducts and the ducts of the Prostate Gland open.

The membranous part begins at the apex of the prostate and reaches the bulb of the penis; its length is 1.5 cm. At this point, the urethra passes through the urogenital Diaphragm, where a voluntary urethral sphincter is formed around it by concentric bundles of striated Muscle fibers.

The spongy part is the longest (about 15 cm) section of the urethra, which runs through the corpus spongiosum of the penis.

The mucosa of the prostatic and membranous PARTS OF THE urethra is lined with Cytology/practical/33.html">Pseudostratified columnar epithelium, the spongy part with simple columnar epithelium, and the region of the glans penis with stratified squamous epithelium.

The female urethra is wider and much shorter than the male; it is a tube 3.0—3.5 cm long and 8—12 mm wide, opening into the Vestibule of the Vagina. Its function is the elimination of urine.

In both males and females, as the urethra passes through the urogenital diaphragm, there is an external sphincter under voluntary control. The internal (involuntary) sphincter is located around the internal urethral orifice and is formed by a circular muscle layer.

The mucosa of the female urethra features longitudinal folds and depressions—urethral lacunae—on its surface, while urethral glands are located within the thickness of the mucosa. The fold on the posterior wall of the urethra is particularly well-developed. The muscular coat consists of outer circular and inner longitudinal layers.