Seminal vesicle

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Seminal vesicle
Male anatomy en.svg
Human Male Anatomy
Gray1160.png
Prostate with seminal vesicles and seminal ducts, viewed from in front and above.
Latin Vesiculae seminales
Gray's p.1246
Artery Inferior vesical artery, middle rectal artery
Lymph External iliac lymph nodes, internal iliac lymph nodes
Precursor Wolffian duct
MeSH Seminal+Vesicles

The seminal vesicles (Latin: glandulae vesiculosae) or vesicular glands [1] are a pair of simple tubular glands posteroinferior to the urinary bladder of some male mammals. Carnivores, marsupials, monotremes, and cetaceans do not have seminal vesicles.[2] Seminal vesicles are located within the pelvis.

Structure[edit]

The seminal vesicles are a pair of glands that are positioned below the bladder and lateral to the ductus deferens. The seminal vesicles are arranged as a series of glands which drain into a central duct. The duct unites with the ductus deferens to form the ejaculatory duct. [3]

The excretory duct of each seminal gland opens into the vas deferens as it enters the prostate gland.

Each seminal vesicle spans approximately 5 cm, though its full unfolded length is approximately 10 cm, but it is curled up inside the gland's structure.

Development[edit]

Each vesicle forms as an outpocketing of the wall of the ampulla of one vas deferens. The seminal vesicles develop as one of three structures of the male reproductive system that develops at the junction between the urethra and vas deferens. Both the urethra and vas deferens are derived from the mesonephric ducts, structures that develop from mesoderm. [4]

Histology[edit]

Under microscopy, the seminal vesicles can be seen to have a mucosa, consisting of a lining of interspersed columnar cells and a laminar propria; and a thick muscular wall. The lumen of the glands is highly irregular and stores secretions from the glands of the vesicles. In detail: [5]

The height of these columnar cells, and therefore activity, is dependent upon testosterone levels in the blood.[citation needed]

  • The lamina propria, containing underlying small blood vessels and lymphatics. Together with the epithelia, this is called the mucosa, and is arranged into convoluted folds, increasing the overall surface area
  • A muscular layer, consisting of an inner circular and outer longitudinal layer of smooth muscle, can also be found.

Spermatazoa may occasionally be found within the lumen of the glands, even though the vesicles are blind-ended in nature. This is thought to be because of slight reflux due to muscular contractions of the urethera during ejaculation. [5]

Function[edit]

The seminal vesicles secrete a significant proportion of the fluid that ultimately becomes semen. Lipofuscin granules from dead epithelial cells give the secretion its yellowish color. About 50-70%[6] of the seminal fluid in humans originates from the seminal vesicles, but is not expelled in the first ejaculate fractions which are dominated by spermatozoa and zinc-rich prostatic fluid. The excretory duct of each seminal gland opens into the corresponding vas deferens as it enters the prostate gland. Seminal vesicle fluid is alkaline, resulting in human semen having a mildly alkaline pH.[7] The alkalinity of semen helps neutralize the acidity of the vaginal tract[citation needed], prolonging the lifespan of sperm. Acidic ejaculate (pH <7.2) may be associated with Ejaculatory duct obstruction. The vesicle produces a substance that causes the semen to become sticky/jelly-like after ejaculation.

The thick secretions from the seminal vesicles contain proteins, enzymes, fructose, mucus, vitamin C, flavins, phosphorylcholine and prostaglandins. The high fructose concentrations provide nutrient energy for the spermatozoa when stored in semen in the laboratory.

In vitro studies have shown that sperm expelled together with seminal vesicular fluid show poor motility and survival, and the sperm chromatin is less protected. Therefore the exact physiological importance of seminal vesicular fluid is not clear.

Additional images[edit]

References[edit]

  1. ^ Wilke; W. Lee Wilke, Rowen D. Frandson, Anna Dee Fails (2009). Anatomy and Physiology of Farm Animals. John Wiley and Sons. ISBN 0-8138-1394-8. Retrieved 2013-11-03. 
  2. ^ http://urology.jhu.edu/newsletter/prostate_cancer511.php
  3. ^ Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell ; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. pp. 407–409. ISBN 978-0-8089-2306-0. 
  4. ^ Larsen's human embryology (4th ed., Thoroughly rev. and updated. ed.). Philadelphia: Churchill Livingstone/Elsevier. 2009. pp. "Development of the urogenital system". ISBN 9780443068119. 
  5. ^ a b Deakin, Barbara Young ... [et al.] ; drawings by Philip J. (2006). Wheater's functional histology : a text and colour atlas (5th ed. ed.). [Edinburgh?]: Churchill Livingstone/Elsevier. p. 355. ISBN 978-0-443-06850-8. 
  6. ^ Kierszenbaum, Abraham L. (2002). Histology and cell biology : an introduction to pathology. St. Louis [u.a.]: Mosby. p. 558. ISBN 0-323-01639-1. 
  7. ^ "CHEMICAL COMPOSITION OF HUMAN SEMEN AND OF THE SECRETIONS OF THE PROSTATE AND SEMINAL VESICLES". http://ajplegacy.physiology.org. Retrieved 2010-08-10. 

External links[edit]

  • BU Histology Learning System: 17501loa - "Male Reproductive System: prostate, seminal vesicle"
  • Anatomy photo:44:04-0202 at the SUNY Downstate Medical Center - "The Male Pelvis: The Urinary Bladder"
  • Anatomy photo:44:08-0103 at the SUNY Downstate Medical Center - "The Male Pelvis: Structures Located Posterior to the Urinary Bladder"