Bartholin’s glands in the female are homologous to what structure in the male?

Bulbo-Urethral Glands

The bulbourethral glands, or Cowper’s glands, are pea-sized structures which lie posterolateral to the intermediate part of the urethra, largely embedded within the external urethral sphincter (Figure 21).

The ducts of these glands open into the proximal part of the spongy urethra in the bulb of the penis and produce a clear, slippery fluid that empties directly into the urethra. This fluid serves to lubricate the urethra and to neutralize any acidity that may be present due to residual drops of urine in the urethra. Their mucus-like secretion enters the urethra during sexual arousal.

The accessory male sex glands—the seminal vesicles, prostate, and bulbourethral glands—produce the seminal plasma

Only 10% of the volume ofsemen (i.e., seminal fluid) is sperm cells. The normal concentration of sperm cells is >20 million per milliliter and the typical ejaculate volume is >2 mL. The typical ejaculate content varies between 150 and 600 million spermatozoa.

Aside from the sperm cells, the remainder of the semen (i.e., 90%) isseminal plasma, the extracellular fluid of semen (Table 54-3). Very little seminal plasma accompanies the spermatozoa as they move through the testes and epididymis. The seminal plasma originates primarily from the accessory glands (the seminal vesicles, prostate gland, and bulbourethral glands). The seminal vesicles contribute ~70% of the volume of semen. Aside from the sperm, the remaining ~20% represents epididymal fluids, as well as secretions of the prostate gland and bulbourethral glands. However, the composition of the fluid exiting the urethral meatus during ejaculation is not uniform. The first fluid to exit is a mixture of prostatic secretions and spermatozoa with epididymal fluid. Subsequent emissions are composed mainly of secretions derived from the seminal vesicles. The first portion of the ejaculate contains the highest density of sperm; it also usually contains a higher percentage of motile sperm cells.

Seminal plasma is isotonic. The pH in the lumen of the epididymis is relatively acidic (6.5 to 6.8) as the result of H+ secretion by clear cells that are analogous to intercalated cells in the nephron (seep. 729). Addition of the relatively alkaline secretions of the seminal vesicles raises the final pH of seminal plasma to between 7.3 and 7.7. Spermatozoa generally tolerate alkalinity better than acidity. A pH near neutrality or slightly higher is optimal for the motility and survival of sperm cells in humans and in other species.

Seminal plasma contains a plethora of sugars and ions. Fructose and citric acid are contributed to the seminal plasma by the accessory glands, and their concentrations vary with the volume of semen ejaculated. Thefructose is produced in the seminal vesicles. In a man with oligospermia (i.e., a low daily sperm output) and a low ejaculate volume (recall that more than half of the ejaculate comes from the seminal vesicles), the absence of fructose suggests obstruction or atresia of the seminal vesicles. Ascorbic acid and traces of B vitamins are also found in human seminal plasma. The prostate gland releases a factor—which contains sugars, sulfate, and a vitamin E derivative—that acts to prevent the clumping of sperm heads. In addition, human semen also contains high concentrations of choline and spermine, and is also rich in Ca2+, Na+, Mg2+, K+, Cl−, Zn2+, and phosphate. Concentrations of Zn2+ and Ca2+ are higher in semen than in any other fluid and most other tissues. Calcium ions stimulate the motility of immature epididymal spermatozoa, but they inhibit the motility of spermatozoa in ejaculates obtained from humans. It appears that the diminished response of sperm to Ca2+ and the acquisition of progressive motility are functions of epididymal maturation.

Benign Penile Disorders

Several benign conditions of the penis may present as palpable masses. Although history and physical examination are the mainstays of diagnosis, MR imaging can play an important role in equivocal cases or in confirming a clinically suspected diagnosis.

Syringocele, Cowper Duct, and Cysts

The bulbourethral glands are two paired periurethral glands situated in the urogenital diaphragm and along the corpus spongiosum of the bulbomembranous and bulbospongious urethra. They were first described by Mery (1684) and William Cowper (1699).21 In girls, the homologous glands are known as Bartholin glands. As depicted in Figure 34-9, the ducts are located within the spongiosus tissue and have small openings into the bulbar urethra. The glands normally secrete a fluid that acts as a lubricant for semen during ejaculation. Colodny and Lebowitz22 were the first to describe reflux of contrast medium into the small ducts during urethrography. In 1983 Maizels and coworkers23 described a classification of dilations of the gland based on clinical characteristics of eight boys. They also introduced the term syringocele (from syrongos, meaning “tube,” and cele, meaning “swelling”).

Rarely, a dilated Cowper gland or duct may be seen as a typical syringocele endoscopically within the urethra, because the membrane can be ruptured or perforated very easily. A syringocele (Fig. 34-10) can cause a urethral obstruction in the neonate (Fig. 34-11). More often, abnormalities of the Cowper ducts are asymptomatic and diagnosed only occasionally (2% to 3%).21 Sometimes, nonspecific symptoms such as dribbling, urgency, urethral obstruction, or hematuria occur.

Reflux into dilated ducts can occur secondary to an anterior obstruction.

The diagnosis of a syringocele or other abnormalities of the Cowper gland or duct is made by antegrade (see Fig. 34-10) or retrograde urethrography and urethroscopy. However, in the situation of late diagnosis, complications such as bleeding or infection may occur. Therefore, in the absence of an abnormal antegrade VCUG or retrograde urethrography and persistent problems such as bleeding or infection, a syringocele or other abnormality of the Cowper gland can be seen by ultrasound of the urethra or by magnetic resonance imaging (Fig. 34-12).

In most cases, spontaneous perforation or rupture requires no further treatment. However, if endoscopic persistence is seen, transurethral incision will solve the problem. Only very few patients require open surgical correction with marsupialization. On rare occasions, secondary dilation due to urethral strictures requires additional or specific treatment.

11.02.2.4.3 Bulbourethral gland

The bulbourethral glands (also called Cowper’s glands) are paired glands that are partially embedded in the urogenital diaphragm muscle and are composed of compound tubuloalveolar glands. While the epithelial cells have a small amount of RER and few lipid droplets, they have an abundance of secretory droplets. Each of the paired glands opens by a single duct (lined with simple cuboidal or columnar epithelium) into the lumen of the cavernous urethra’s proximal portion. While the secretions are mucus-like, they are different from true mucus: they are not precipitated with acetic acid as true mucus is, and they can be drawn out into a long thin thread. The gland has limited ability to store secretions; therefore, when the muscles contract with erection, the gland’s secretions are released into the urethra and will seep out of the penile urethra at the glans penis upon prolonged erection. These secretions function as a lubricant and remove urine in the tract prior to ejaculation. They may also be important in inducing gelation of the seminal plasma in species such as the boar (Fawcett 1986).

Using the split ejaculate technique in humans, the first part of the ejaculate appears to be from the prostate, followed by subsequent secretions from the ductus deferens and seminal vesicles. The first part of the ejaculate contains most (∼>80%) of the citrate, the second part most (∼>80%) of the spermatozoa, and the third part most (>80%) of the fructose. The presence of these different items in semen can be sued to locate a blockage when no sperms are found in the ejaculate. Semen collection procedures for stallions and boars utilize filters that allow prostatic fluids and spermatozoa to pass while preventing the gel from the seminal vesicle (which is ejaculated last) to mix with the gel-free semen (which is ejaculated first). Characteristics of fertile human ejaculates include >20 × 106 spermatozoa per ml, >80% spermatozoa with normal morphology, >60% progressively motile spermatozoa, good viscosity (semen that will clot then disperse), and about 3 ml of volume to raise the pH in the vagina upon deposition.

Histology

Histologically, the bulbourethral glands are multilobular. Each lobule is composed of acini that open into a centrally located canal. A thin capsule of fibrous connective tissue surrounds and separates the acini. In mice, the glandular acini are highly arborized and lined by tall columnar epithelium. In the secretory state, the epithelium has abundant, foamy cytoplasm, and in the resting state, the cytoplasm is eosinophilic and finely granular. The secretory cells are found mainly in the body, and the resting cells are found in the tail (Fig. 18.16). The ductular epithelium is cuboidal. Older mice may develop cystic bulbourethral glands that may result in swelling of the perineal region and impaired reproductive performance. Bacterial infections with Staphylococcus aureus and Pasteurella pneumotropica are also common.