Seminal vesicle

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E.Mangoli

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The seminal vesicles are paired, elongate, and highly folded tubular glands located on the posterior wall of the urinary bladder, parallel to the ampulla of the ductus deferens.

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The secretion of the seminal vesicles is a whitish yellow, viscous material.

It contains:

 fructose, which is the principal metabolic substrate for sperm amino acids, ascorbic acid, prostaglandins: E, A, B, F

 coagulating factor semenogelin 1: sperm motility inhibitor, which is cleaved by PSA (proteolytic enzyme) after ejaculation

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Contraction of the smooth muscle coat of the seminal vesicles during ejaculation discharges their secretion into the ejaculatory ducts and helps to flush sperm out of the urethra.

The secretory function and morphology of the seminal vesicles are under

the control of testosterone.

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The prostate is the largest accessory sex gland of the male reproductive system.

The gland is located in the pelvis, inferior to the bladder, where it surrounds the prostatic part of the urethra.

The prostate is composed of approximately

70% glandular elements and 30% fibromascular stroma.

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It consists of 30 to 50 tubuloalveolar glands arranged in three concentric layers:

 an inner mucosal layer, an intermediate submucosal layer, a peripheral layer containing the main prostatic glands.

The glands of the mucosal layer secrete directly into the urethra; the other two layers have ducts that open into the prostatic sinuses located on either side of the urethral crest on the posterior wall of the urethra.

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The adult prostatic parenchyma is divided into four anatomically and clinically distinct zones:

 peripheral zone central zone transitional zone periurethral zone

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The prostate gland secretes:

 prostatic acid phosphatase (PAP), fibrinolysin, (serves to liquefy the semen) citric acid, prostate-specific antigen (PSA). (a serine protease) polyamines: proliferation and growth calcium, phosphate ion, clotting enzyme,

Profibrinolysin, zinc.

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The elevated levels of PSA are directly related to increased activity of the prostatic cancer cells.

Increased blood levels of both PAP and PSA are used as markers of the presence and progression of the disease.

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The bulbourethral glands secrete preseminal fluid

The paired bulbourethral glands (Cowper's glands) are pea-sized structures located in the urogenital diaphragm.

The duct of each gland passes through the inferior fascia of the urogenital diaphragm and joins the initial portion of the penile urethra.

The glands are compound tubuloalveolar glands that structurally resemble mucus secretory glands.

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The clear, mucuslike glandular secretion contains considerable amounts of :

 galactose and galactosamine, galacturonic acid, sialic acid, methylpentose.

Sexual stimulation causes release of the secretion, which constitutes the major portion of the preseminal fluid and probably serves to lubricate the penile urethra.

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The secretion from seminal vesicles contribute approximately 50-80 % of the ejaculate volume, with an average volume of

2.5 ml and a pH in neutral to alkaline range.

The average volume of semen: 3 ml (2-6)

Seminal vesicle: 1.5-2 ml

Prostate: 0.5 ml (15-30%)

Bulourethral and littre glands: 0.1-0.2 ml

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The initial portion of the ejaculate contains the highest number of spermatozoa ; is rich in acid phosphatase, citric acid, and zinc; and has a lower pH due to prostatic fluid. The remainder of the ejaculate largely comprises seminal vesicle fluid, which contains a high concentration of fructose and has a higher pH.

Normal pH of collected semen ranges from 7.2 to

7.7

and becomes more alkaline after ejaculation and as time passes.

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Most seminal plasma is produced by the prostate and seminal vesicles, while the testis and epididymis contribute less than 5% of the total semen volume.

A low ejaculate volume reflects abnormality of the prostate or seminal vesicles.

Fructose is produced by the seminal vesicles; thus the absence of fructose indicates either ejaculatory duct obstruction or seminal vesicle aplasia/hypoplasia or cogenital bilateral absence of the vas deferens.

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This adds greatly to the bulk of the ejaculated semen, and the fructose and other substances in the seminal fluid are of considerable nutrient value for the ejaculated sperm until one of the sperm fertilizes the ovum.

Prostaglandins are believed to aid fertilization in two ways:

 reacting with the female cervical mucus to make it more receptive to sperm movement possibly causing backward, reverse peristaltic contractions in the uterus and fallopian tubes to move the ejaculated sperm toward the ovaries (a few sperm reach the upper ends of the fallopian tubes within 5 minutes).

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• A slightly alkaline characteristic of the prostatic fluid may be quite important for successful fertilization of the ovum, because the fluid of the vas deferens is relatively acidic owing to the presence of citric acid and metabolic end products of the sperm and, consequently, helps to inhibit sperm fertility.

Also, the vaginal secretions of the female are acidic (pH of 3.5 to 4.0). Sperm do not become optimally motile until the pH of the surrounding fluids rises to about 6.0 to 6.5.

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Approximately 10% of infertile men have blockages in the genital tract causing absence of sperm in the semen.

There are four major groups of causes of male genital tract blockages:

 disorders of development of the epididymis, vas and seminal vesicles, post inflammatory epididymal obstructions

(especially from gonorrhea), vasal obstructions (vasectomy) ejaculatory duct obstructions.

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A 20- 30% pregnancy rate can be expected from surgical treatment in which the obstruction is removed endoscopically, and

70% of men who undergo the procedure will achieve a significant improvement in semen quality.

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Examination of the prostate gland is by rectal examination preferentially with the man in the knee-elbow position.

The seminal vesicles are not normally palpable. If they are palpable and/or painful upon pressure this usually indicates inflammation. In general, seminal vesiculitis is accompanied by prostatitis.

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Male accessory gland infection (MAGI) is a general denominator for infection/inflammation of the prostate glands, seminal vesicles, and/or epididymis.

MAGI may result from infection by sexually transmitted pathogens (e.g., Chlamydia trachomatis) or, more commonly, trivial urinary pathogens such as E. coli, Proteus species, enterococci, or Pseudomonas species.

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Include: prostatitis, epididimytis, urethritis orchitis,

Potentially

curable

cause of male infertility

Controversy: Are these disease have a negative effect on sperm quality and male infertility

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Depending on the severity and the duration of the disease and on the site of infection, the effects on sperm quality and fertility are largely variable.

The prevalence of MAGI among infertile men is different (In Europe and in North America

8–10%).

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1- Urethritis

2- Epididymitis

3- Prostatovesiculitis

4- Silent inflammation

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1- Gonorrhea

2- Chlamydia Trichomatis

3- Mycoplasma spp.

4- Ureaplasma Urealyticum

5- E. Coli,

6- Proteus species,

7- Enterococci,

8- Pseudomonas species.

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1- Direct damage

2- Inflammation

3- Increase ROS production

4-Obstruction of seminal ducts

5- Antibody formation

6- Ejaculatory dysfunction

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The effects of MAGI on the fertilizing capacity of spermatozoa :

 decreased ejaculate volume

 increased viscosity abnormal biochemical composition of the seminal fluid, poor sperm motility, low sperm concentration high concentration of ROS, diminished production of antioxidants by the epididymides damage the sperm membrane with decreased acrosomal reactivity and poor capacity to fuse with the oocyte membrane and cause DNA damage.

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Semen analysis may reveal:

 subnormal ejaculate volume, increased viscosity, alkaline pH, low concentration of citric acid and of other markers of prostate function below normal alpha-glucosidase activity in case of epididymal damage. poor sperm motility, low sperm count, poor sperm morphology: high number of round cells.

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The diagnosis of MAGI is based on:

 medical history, the physical examination, echography cytological and bacteriological analysis of urine and blood.

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MAGI should be treated for reasons of ‘‘good medical practice,’’ but the effects of treatment on sperm quality and fertility are limited.

Indeed, in the majority of cases, the function of the accessory sex glands is irreversibly damaged.

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Male accessory gland infection has different deleterious effects on fertility, depending on the site that is affected.

Antibiotic treatment has little advantage for fertility, but is indicated for reasons of good medical practice if signs and symptoms of actual infection are found.

Complementary prescription of a specific combination of natural antioxidants and antiinflammatory substances can help to correct some of the damage to spermatozoa caused by

MAGI.

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