Male Urogenital Triangle-Penis-Scrotum-Testes-Epididymides-Female Urogenital Triangle-Vulva-Mons Pubis-Labia Majora-Labia Minora-Vestibule-Vaginal Orifice-Clitoris

Male Urogenital Triangle

The male urogenital triangle contains the penis and the scrotum.

Penis

The penis consists of a root, a body, and a glans. The root of the penis consists of three masses of erectile tissue called the bulb of the penis and the right and left crura of the penis. The bulb can be felt on deep palpation in the midline of the perineum, posterior to the scrotum.

The body of the penis is the free portion of the penis, which is suspended from the symphysis pubis. Note that the dorsal surface (anterior surface of the flaccid organ) usually possesses a superficial dorsal vein in the midline The glans penis forms the extremity of the body of the penis. At the summit of the glans is the external urethral meatus. Extending from the lower margin of the external meatus is a fold connecting the glans to the prepuce called the frenulum. The edge of the base of the glans is called the corona. The prepuce or foreskin is formed by a fold of skin attached to the neck of the penis. The prepuce covers the glans for a variable extent, and it should be possible to retract it over the glans.

Scrotum

The scrotum is a sac of skin and fascia containing the testes and the epididymides. The skin of the scrotum is rugose and is covered with sparse hairs. The bilateral origin of the scrotum is indicated by the presence of a dark line in the midline, called the scrotal raphe, along the line of fusion
.

Testes

The testes should be palpated. They are oval shaped and have a firm consistency. They lie free within the tunica vaginalis and are not tethered to the subcutaneous tissue or skin.

Epididymides

Each epididymis can be palpated on the posterolateral surface of the testis. The epididymis is a long, narrow, firm structure having an expanded upper end or head, a body, and a pointed tail inferiorly. The cordlike vas deferens emerges from the tail and ascends medial to the epididymis to enter the spermatic cord at the upper end of the scrotum.

Female Urogenital Triangle

Vulva

“Vulva” is the term applied to the female external genitalia

Mons Pubis

The mons pubis is the rounded, hair-bearing elevation of skin found anterior to the pubis. The pubic hair in the female has an abrupt horizontal superior margin, whereas in the male it extends upward to the umbilicus.

Labia Majora

The labia majora are prominent, hair-bearing folds of skin extending posteriorly from the mons pubis to unite posteriorly in the midline
.

Labia Minora

The labia minora are two smaller, hairless folds of soft skin that lie between the labia majora . Their posterior ends are united to form a sharp fold, the fourchette. Anteriorly, they split to enclose the clitoris, forming an anterior prepuce and a posterior frenulum

Vestibule

The vestibule is a smooth triangular area bounded laterally by the labia minora, with the clitoris at its apex and the fourchette at its base.

Vaginal Orifice

The vaginal orifice is protected in virgins by a thin mucosal fold called the hymen, which is perforated at its center. At the first coitus, the hymen tears, usually posteriorly or posterolaterally, and after childbirth only a few tags of the hymen remain .

Clitoris

This is situated at the apex of the vestibule anteriorly. The glans of the clitoris is partly hidden by the prepuce.

Penis-Root of the Penis-Body of the Penis-Blood Supply-Arteries-Veins-Lymph Drainage-Rupture of the Urethra- Erection and Ejaculation after Spinal Cord Injuries -Urethral Infection

Penis

The penis has a fixed root and a body that hangs free

Root of the Penis

The root of the penis is made up of three masses of erectile tissue called the bulb of the penis and the right and left crura of the penis. The bulb is situated in the midline and is attached to the undersurface of the urogenital diaphragm. It is traversed by the urethra and is covered on its outer surface by the bulbospongiosus muscles. Each crus is attached to the side of the pubic arch and is covered on its outer surface by the ischiocavernosus muscle. The bulb is continued forward into the body of the penis and forms the corpus spongiosum. The two crura converge anteriorly and come to lie side by side in the dorsal part of the body of the penis, forming the corpora cavernosa.

 

Body of the Penis

The body of the penis is essentially composed of three cylinders of erectile tissue enclosed in a tubular sheath of fascia (Buck’s fascia). The erectile tissue is made up of two dorsally placed corpora cavernosa and a single corpus spongiosum applied to their ventral surface. At its distal extremity, the corpus spongiosum expands to form the glans penis, which covers the distal ends of the corpora cavernosa. On the tip of the glans penis is the slitlike orifice of the urethra, called the external urethral meatus.

The prepuce or foreskin is a hoodlike fold of skin that covers the glans. It is connected to the glans just below the urethral orifice by a fold called the frenulum.

The body of the penis is supported by two condensations of deep fascia that extend downward from the linea alba and symphysis pubis to be attached to the fascia of the penis.

 

Blood Supply

Arteries

The corpora cavernosa are supplied by the deep arteries of the penis; the corpus spongiosum is supplied by the artery of the bulb. In addition, there is the dorsal artery of the penis. All the above arteries are branches of the internal pudendal artery.

 

Veins

The veins drain into the internal pudendal veins.

Lymph Drainage

The skin of the penis is drained into the medial group of superficial inguinal nodes. The deep structures of the penis are drained into the internal iliac nodes

Nerve Supply

The nerve supply is from the pudendal nerve and the pelvic plexuses.

Rupture of the Urethra

Rupture of the urethra may complicate a severe blow on the perineum. The common site of rupture is within the bulb of the penis, just below the perineal membrane. The urine extravasates into the superficial perineal pouch and then passes forward over the scrotum beneath the membranous layer of the superficial fascia,. If the membranous part of the urethra is ruptured, urine escapes into the deep perineal pouch and can extravasate upward around the prostate and bladder or downward into the superficial perineal pouch.

  Erection and Ejaculation after Spinal Cord Injuries

Erection of the penis is controlled by the parasympathetic nerves that originate from the 2nd, 3rd, and 4th sacral segments of the spinal cord. Bilateral damage to the reticulospinal nerve tracts in the spinal cord will result in loss of erection. Later, when the effects of spinal shock have disappeared, spontaneous or reflex erection may occur if the sacral segments of the spinal cord are intact.

Ejaculation is controlled by sympathetic nerves that originate in the 1st and 2nd lumbar segments of the spinal cord. As in the case of erection, severe bilateral damage to the spinal cord results in loss of ejaculation. Later, reflex ejaculation may be possible in patients with spinal cord transections in the thoracic or cervical regions.

Urethral Infection

The most dependent part of the male urethra is that which lies within the bulb. Here, it is subject to chronic inflammation and stricture formation.

The many glands that open into the urethra—including those of the prostate, the bulbourethral glands, and many small penile urethral glands—are commonly the site of chronic gonococcal infection.

Injuries to the penis may occur as the result of blunt trauma, penetrating trauma, or strangulation. Amputation of the entire penis should be repaired by anastomosis using microsurgical techniques to restore continuity of the main blood vessels.

Scrotum-Blood Supply-Erection of the Penis-Ejaculation-Friction on the glans penis-Male Urethra

Scrotum

The scrotum is an outpouching of the lower part of the anterior abdominal wall and contains the testes, the epididymides, and the lower ends of the spermatic cords

The wall of the scrotum has the following layers:

■■ Skin

■■ Superficial fascia; the dartos muscle, which is smooth muscle, replaces the fatty layer of the anterior abdominal wall, and Scarpa’s fascia (membranous layer), now called Colles’ fascia.

■■ External spermatic fascia derived from the external oblique

■■ Cremasteric fascia derived from the internal oblique

■■ Internal spermatic fascia derived from the fascia transversalis

■■ Tunica vaginalis, which is a closed sac that covers the anterior, medial, and lateral surfaces of each testis Because the structure of the scrotum, the descent of the testes, and the formation of the inguinal canal are interrelated

Blood Supply

Subcutaneous plexuses and arteriovenous anastomoses promote heat loss and thus assist in the environmental control of the temperature of the testes.

Arteries

The external pudendal branches of the femoral and scrotal branches of the internal pudendal arteries supply the scrotum.

Veins

The veins accompany the corresponding arteries.

Erection of the Penis

Erection in the male is gradually built up as a consequence of various sexual stimuli. Pleasurable sight, sound, smell, and other psychic stimuli, fortified later by direct touch sensory stimuli from the general body skin and genital skin, result in a bombardment of the central nervous system by afferent stimuli. Efferent nervous impulses pass down the spinal cord to the parasympathetic outflow in the second, third, and fourth sacral segments. The parasympathetic preganglionic fibers enter the inferior hypogastric plexuses and synapse on the postganglionic neurons. The postganglionic fibers join the internal pudendal arteries and are distributed along their branches, which enter the erectile tissue at the root of the penis. Vasodilatation of the arteries now occurs, producing a great increase in blood flow through the blood spaces of the erectile tissue. The corpora cavernosa and the corpus spongiosum become engorged with blood and expand, compressing their draining veins against the surrounding fascia. By this means, the outflow of blood from the erectile tissue is retarded so that the internal pressure is further accentuated and maintained. The penis thus increases in length and diameter and assumes the erect position. Once the climax of sexual excitement is reached and ejaculation takes place, or the excitement passes off or is inhibited, the arteries supplying the erectile tissue undergo vasoconstriction. The penis then returns to its flaccid state

Ejaculation

During the increasing sexual excitement that occurs during sex play, the external urinary meatus of the glans penis becomes moist as a result of the secretions of the bulbourethral glands

Friction of the glans penis

reinforced by other afferent nervous impulses, results in a discharge along the sympathetic nerve fibers to the smooth muscle of the duct of the epididymis and the vas deferens on each side, the seminal vesicles, and the prostate. The smooth muscle contracts, and the spermatozoa, together with the secretions of the seminal vesicles and prostate, are discharged into the prostatic urethra. The fluid now joins the secretions of the bulbourethral glands and penile urethral glands and is then ejected from the penile urethra as a result of the rhythmic contractions of the bulbospongiosus muscles, which compress the urethra. Meanwhile, the sphincter of the bladder contracts and prevents a reflux of the spermatozoa into the bladder. The spermatozoa and the secretions of the several accessory glands constitute the seminal fluid, or semen. At the climax of male sexual excitement, a mass discharge of nervous impulses takes place in the central nervous system. Impulses pass down the spinal cord to the sympathetic outflow (T1 to L2). The nervous impulses that pass to the genital organs are thought to leave the cord at the first and second lumbar segments in the preganglionic sympathetic fibers. Many of these fibers synapse with postganglionic neurons in the first and second lumbar ganglia. Other fibers may synapse in ganglia in the lower lumbar or pelvic parts of the sympathetic trunks. The postganglionic fibers are then distributed to the vas deferens, the seminal vesicles, and the prostate via the inferior hypogastric plexuses.

Male Urethra

The male urethra is about 8 in. (20 cm) long and extends from the neck of the bladder to the external meatus on the glans penis. It is divided into three parts: prostatic, membranous, and penile.

The prostatic urethra is described on page 278. It is about 1.25 in. (3 cm) long and passes through the prostate from the base to the apex. It is the widest and most dilatable portion of the urethra. The membranous urethra is about 0.5 in. (1.25 cm) long and lies within the urogenital diaphragm, surrounded by the sphincter urethrae muscle. It is the least dilatable portion of the urethra.

The penile urethra is about 6 in. (15.75 cm) long and is enclosed in the bulb and the corpus spongiosum of the penis. The external meatus is the narrowest part of the entire urethra. The part of the urethra that lies within the glans penis is dilated to form the fossa terminalis (navicular fossa). The bulbourethral glands open into the penile urethra below the urogenital diaphragm.