Bulbourethral gland

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Bulbourethral gland
Male anatomy 1.png
Male anatomy
Bulbourethral gland -- very high mag.jpg
Micrograph of bulbourethral gland. H&E stain.
Details
Precursor Urogenital sinus
System Male reproductive system
Artery Artery of the urethral bulb
Identifiers
Latin glandula bulbourethralis
MeSH D002030
TA98 A09.3.09.001
TA2 3659
Anatomical terminology

The bulbourethral glands or Cowper's glands (named for English anatomist William Cowper) are two small exocrine and accessory glands in the reproductive system of many male mammals. [1] They are homologous to Bartholin's glands in females. The bulbourethral glands are responsible for producing a pre-ejaculate fluid called Cowper's fluid (known colloquially as pre-cum), which is secreted during sexual arousal, neutralizing the acidity of the urethra in preparation for the passage of sperm cells. [2] The paired glands are found adjacent to the urethra just below the prostate, seen best by screening (medicine) MRI as a tool in preventative healthcare in males. Screening MRI may be performed when there is a positive prostate-specific antigen on basic laboratory tests. Prostate cancer is the second-most common cause of cancer-related mortality in males in the USA.

Contents

Most species of placental mammals have bulbourethral glands, but they are absent in whales, dolphins, and porpoises. They are the only accessory reproductive glands in male monotremes. Placental mammals usually have 1 pair of bulbourethral glands, [3] while male marsupials have 1–3 pairs. [3] [4] [5] Of all domesticated animals, they are absent only in dogs. [6]

Location

Bulbourethral glands are located posterior and lateral to the membranous portion of the urethra at the base of the penis, between the two layers of the fascia of the urogenital diaphragm, in the deep perineal pouch. They are enclosed by transverse fibers of the sphincter urethrae membranaceae muscle.

Structure

Dissection of prostate showing the bulbourethral glands within the fibers of the external urethral sphincter just underneath the prostate Prostatic urethra.svg
Dissection of prostate showing the bulbourethral glands within the fibers of the external urethral sphincter just underneath the prostate

The bulbourethral glands are compound tubulo-alveolar glands, each approximately the size of a pea in humans. In chimpanzees, they are not visible during dissection, but can be found on microscopic examination. [7] In boars, they are up to 18 cm long and 5 cm in diameter. [6] They are composed of several lobules held together by a fibrous covering. Each lobule consists of a number of acini, lined by columnar epithelial cells, opening into a duct that joins with the ducts of other lobules to form a single excretory duct. This duct is approximately 2.5 cm long and opens into the bulbar urethra at the base of the penis. The glands gradually diminish in size with advancing age. [8] [ unreliable source ]

Function

Secretory fluid from the bulbourethral glands appearing on the glans of a human penis Pre cum 160717.jpg
Secretory fluid from the bulbourethral glands appearing on the glans of a human penis

The bulbourethral gland contributes up to 4 ml of fluid during sexual arousal. [9] The secretion is a clear fluid rich in mucoproteins that help to lubricate the distal urethra and neutralize any acidic urine residue that remains in the urethra.

According to one preliminary study, the bulbourethral gland fluid might not contain any sperm, [10] whereas another study showed some men did leak sperm in potentially significant quantities (in a range from low counts up to 50 million sperm per ml) into the pre-ejaculatory fluid, [9] potentially leading to conception from the introduction of pre-ejaculate. However, the sperm source is a residual or pre-ejaculatory leak from the testicles into the vasa deferentia, [9] rather than from the bulbourethral gland itself. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Urethra</span> Tube that connects the urinary bladder to the external urethral orifice

The urethra is the tube that connects the mammalian urinary bladder to the urinary meatus. In placental mammals, the urethra transports urine through the penis or vulva during urination and semen through the penis during ejaculation.

<span class="mw-page-title-main">Prostate</span> Gland of the male reproductive system

The prostate is both an accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemically, and physiologically. Anatomically, the prostate is found below the bladder, with the urethra passing through it. It is described in gross anatomy as consisting of lobes and in microanatomy by zone. It is surrounded by an elastic, fibromuscular capsule and contains glandular tissue, as well as connective tissue.

<span class="mw-page-title-main">Skene's gland</span> Glands located on the anterior wall of the vagina

In female human anatomy, Skene's glands or the Skene glands are glands located around the lower end of the urethral meatus. The glands are surrounded by tissue that swells with blood during sexual arousal, and secrete a fluid from openings near the urethra, particularly during orgasm.

<span class="mw-page-title-main">Pre-ejaculate</span> Clear fluid emitted from the urethra of the penis during arousal

Pre-ejaculate is a clear, colorless, viscous fluid that is emitted from the urethra of the penis during sexual arousal and in general during sexual activity. It is similar in composition to semen but has distinct chemical differences. The presence of sperm in the fluid is variable from low to absent. Pre-ejaculate functions as a lubricant and an acid neutralizer.

<span class="mw-page-title-main">Retrograde ejaculation</span> Redirection of ejaculated semen into the urinary bladder

Retrograde ejaculation occurs when semen which would be ejaculated via the urethra is redirected to the urinary bladder. Normally, the sphincter of the bladder contracts before ejaculation, inhibiting urination and preventing a reflux of semen into the bladder. The semen is forced to exit via the urethra, the path of least resistance. When the bladder sphincter does not function properly, retrograde ejaculation may occur. It can also be induced deliberately by a male as a primitive form of male birth control or as part of certain alternative medicine practices. The retrograde-ejaculated semen is excreted from the bladder during the next urination.

<span class="mw-page-title-main">Seminal vesicles</span> Pair of simple tubular glands

The seminal vesicles are a pair of convoluted tubular accessory glands that lie behind the urinary bladder of male mammals. They secrete fluid that partly composes the semen.

<span class="mw-page-title-main">Vas deferens</span> Part of the male reproductive system of many vertebrates

The vas deferens, with the more modern name ductus deferens, is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymides to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube which exits the abdominal cavity through the inguinal canal.

<span class="mw-page-title-main">Ejaculatory duct</span> Male anatomical structures

The ejaculatory ducts are paired structures in the male reproductive system. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra above the seminal colliculus. During ejaculation, semen passes through the prostate gland, enters the urethra and exits the body via the urinary meatus.

<span class="mw-page-title-main">Urogenital sinus</span> Embryological part during the development of the urinary and reproductive organs in mammals

The urogenital sinus is a body part of a human or other placental only present in the development of the urinary and reproductive organs. It is the ventral part of the cloaca, formed after the cloaca separates from the anal canal during the fourth to seventh weeks of development.

<span class="mw-page-title-main">Male reproductive system</span> Reproductive system of the human male

The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the body, and within the pelvis.

<span class="mw-page-title-main">Human reproductive system</span> Organs involved in reproduction

The human reproductive system includes the male reproductive system, which functions to produce and deposit sperm, and the female reproductive system, which functions to produce egg cells and to protect and nourish the fetus until birth. Humans have a high level of sexual differentiation. In addition to differences in nearly every reproductive organ, there are numerous differences in typical secondary sex characteristics.

Aspermia is the complete lack of semen with ejaculation. It is associated with infertility.

<span class="mw-page-title-main">Human penis</span> Human male external reproductive organ

In human anatomy, the penis is an external male sex organ that serves as a passage for excretion of urine and ejaculation of semen. The main parts are the root, body, the epithelium of the penis including the shaft skin, and the foreskin covering the glans. The body of the penis is made up of three columns of tissue: two corpora cavernosa on the dorsal side and corpus spongiosum between them on the ventral side. The urethra passes through the prostate gland, where it is joined by the ejaculatory ducts, and then through the penis. The urethra goes across the corpus spongiosum and ends at the tip of the glans as the opening, the urinary meatus.

The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system, the two systems are typically described together as the genitourinary system.

<span class="mw-page-title-main">Semen</span> Reproductive biofluid of male or hermaphroditic animals

Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoa. Spermatozoa are secreted by the male gonads and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. In placental mammals, semen also contains secretions from the male accessory glands and is discharged from the penis through the urethral orifice during ejaculation. In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa and provide a medium through which they can move or "swim". The fluid is adapted to be discharged deep into the vagina, so the spermatozoa can pass into the uterus and form a zygote with an egg.

The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.

<span class="mw-page-title-main">Ejaculation</span> Euphoric stimulative semen discharge of the male reproductive tract

Ejaculation is the discharge of semen through the urethra in men. It is normally linked with orgasm, which involves involuntary contractions of the pelvic floor. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. Ejaculation can occur spontaneously during sleep, and is a normal part of human sexual development. In rare cases, ejaculation occurs because of prostatic disease. Anejaculation is the condition of being unable to ejaculate. Ejaculation is normally intensely pleasurable for men; dysejaculation is an ejaculation that is painful or uncomfortable. Retrograde ejaculation is the backward flow of semen into the bladder rather than out of the urethra.

<span class="mw-page-title-main">Male accessory gland</span> Sexual gland in males

Male accessory glands (MAG) are the seminal vesicles, prostate gland, and the bulbourethral glands. These glands are found only in mammals. In insects, male accessory glands produce products that mix with the sperm to protect and preserve them, including seminal fluid proteins. Some insecticides can induce an increase in the protein content of the male accessory glands of certain types of insects. This has the unintended effect of increasing the number of offspring they produce.

<span class="mw-page-title-main">Reproductive system of planarians</span>

The reproductive system of planarians is broadly similar among different families, although the associated structures can vary in complexity.

The monotremes represent the order of extant mammals most distantly related to humans. The platypus is indigenous to eastern Australia; the short-beaked echidna is indigenous to Australia and Papua New Guinea; whereas the long-beaked echidna is restricted to Papua New Guinea and Irian Jaya. Since monotremes exhibit characteristics common with both reptiles and therian mammals, they are of great interest for the study of mammalian evolution.

References

  1. Liebich, Hans-Georg (2019-10-31). Veterinary Histology of Domestic Mammals and Birds 5th Edition: Textbook and Colour Atlas. 5m Books Ltd. ISBN   978-1-78918-106-7.
  2. "What is pre-ejaculatory fluid (also known as pre-cum), and can it cause pregnancy?". International Planned Parenthood Federation. 13 February 2019. Retrieved 21 July 2019.
  3. 1 2 Dixson, Alan F. (2021-06-03). Mammalian Sexuality: The Act of Mating and the Evolution of Reproduction. Cambridge University Press. ISBN   978-1-108-69949-5.
  4. Armati, Patricia J.; Dickman, Chris R.; Hume, Ian D. (2006-08-17). Marsupials. Cambridge University Press. ISBN   978-1-139-45742-2.
  5. Tyndale-Biscoe, C. Hugh; Renfree, Marilyn (1987-01-30). Reproductive Physiology of Marsupials. Cambridge University Press. ISBN   978-0-521-33792-2.
  6. 1 2 Mark McEntee (December 2, 2012). Reproductive Pathology of Domestic Mammals. Elsevier Science. p. 333. ISBN   978-0-323-13804-8 . Retrieved August 20, 2013.
  7. Jeffrey H. Schwartz (1988). Orang-utan Biology. Oxford University Press. p. 92. ISBN   978-0-19-504371-6 . Retrieved August 20, 2013.
  8. Gray's Anatomy , 38th ed., p 1861.
  9. 1 2 3 Killick, S. R; Leary, C; Trussell, J; Guthrie, K. A (2010). "Sperm content of pre-ejaculatory fluid". Human Fertility. 14 (1): 48–52. doi:10.3109/14647273.2010.520798. PMC   3564677 . PMID   21155689.
  10. 1 2 Zukerman, Z; Weiss, D. B; Orvieto, R (2003). "Short Communication: Does Preejaculatory Penile Secretion Originating from Cowper's Gland Contain Sperm?". Journal of Assisted Reproduction and Genetics. 20 (4): 157–159. doi:10.1023/A:1022933320700. PMC   3455634 . PMID   12762415.