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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 vesiculæ seminales
Gray's subject #260 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 (glandulae vesiculosae) or vesicular glands [1] are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals.

Contents

Anatomy

Each seminal gland spreads approximately 5 cm, though the full length of seminal vesicle is approximately 10 cm, but it is curled up inside of the gland's structure. Each gland forms as an outpocketing of the wall of ampulla of each vas deferens.

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

Function

The seminal vesicles secrete a significant proportion of the fluid that ultimately becomes semen. Lipofuscin granules from dead epithelial cells gives the secretion its yellowish color. About 60% 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 along with the prostatic fluid, resulting in human semen having a mildly alkaline pH.[2] The alkalinity of semen helps neutralize the acidity of the vaginal tract, prolonging the lifespan of sperm. Acidic ejaculate (pH <7.2) may be associated with blockage of seminal vesicles.

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. Spermatozoa ejaculated in the vagina are not likely to have contact with the seminal vesicular fluid but transfer directly from the prostatic fluid into the cervical mucus as the first step on their travel through the female reproductive system. The fluid is expelled under sympathetic contraction of the muscularis muscle coat.

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. It has been speculated that it is a developmental rest, still seen among some rodents where the last part of the ejaculate form a spermicidal plug which reduces the chances for sperm from a later arriving male to proceed to the oocyte.[citation needed]

Histology

Histologically, the seminal vesicles are notable for their tortuous pathways, diverticula, pseudo-stratified columnar epithelium and cuboidal cells along the basal layer.

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

The lumen is large and stores the fluid secretions (but not spermatozoa) between ejaculations.

From inside to out, the layers are:

  • Mucosa - arranged into convoluted folds, significantly increasing surface area
  • Muscular - well-developed layer composed of an inner circular and outer longitudinal layer of smooth muscle
  • Connective tissue[citation needed]

Additional images

External links

References

  1. ^ Wilke; W. Lee Wilke, Rowen D. Frandson, Anna Dee Fails (2009). Anatomy and Physiology of Farm Animals. John Wiley and Sons. ISBN 0813813948. http://books.google.com/books?id=I9ZZkwnFLN0C&pg=PT423&dq=Vesicular+gland&as_brr=3&client=firefox-a#v=onepage&q=Vesicular%20gland&f=false. 
  2. ^ "SEMEN ANALYSIS". www.umc.sunysb.edu. http://www.umc.sunysb.edu/urology/male_infertility/SEMEN_ANALYSIS.html. Retrieved 2009-04-28. 

Simple English

[[File:|200px|thumb|right|A diagram of the seminal vesticles]] The seminal vesicles are a pair of tube-like glands. They are found behind the bladder of males. They make a large most of the content of semen (also called seminal fluid). About 70% of the seminal fluid in humans comes from the seminal vesicles.

Contents

Anatomy

Both vesicles are about 5 cm in length, but it is curled up. Each gland makes a ball shape on the wall of each vas deferens. There is a tube linking the seminal glands which opens into the vas deferens and prostate gland.

From inside to out, the layers making the vesicles are:

Use

The seminal vesicles make most of semen, but during ejaculation, most of the ejaculate has sperm rather than semen in it. The use of seminal fluid is not known, since sperm do not move or survive well in semen. Some think that it acts as a fluid to stop sperm from another male impregnating the female so that the children of only one male can survive.

Seminal fluid has proteins, enzymes, fructose, mucus, vitamin C and flavins. The fructose gives sperm energy and 'food'.

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