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Seminal Vesicles

The seminal vesicles or vesicular glands are a pair of simple tubular glands posteroinferior to the urinary bladder of male mammals. It is located within the pelvis. 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% 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. 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 ejaculatory duct obstruction. The vesicle produces a substance that causes the semen to become sticky/jelly-like after ejaculation, which is thought to be useful in keeping the semen near the womb. The seminal vesicles can be manually examined via palpation with the index finger in the rectal vault and the finger pad directed anteriorly. The seminal vesicles lie immediately superior to the prostate gland. Although the prostate gland can be readily felt, the seminal vesicles are not normally felt. However, in the instance of chronic infection or advanced cancer of the prostate, the glands may feel harden. Their cystic masses may also be felt on palpation and are typically embryologic remnants of the paramesonephric ducts. Primary carcinoma of the seminal vesicles is very uncommon.