Seminal Plasma

Definition - What does Seminal Plasma mean?

Seminal plasma is the fluid medium in semen that suspends the sperm cells. Seminal plasma contains sugars, protein, oxygen, minerals, and ions and provides the nutrition to the sperms while protecting it from the outside environment as sperm travel across the vagina and uterus to the fallopian tubes to fertilize an egg. Reduced production or the blockage of flow, or any abnormality in the composition of seminal plasma can interfere with the ability of sperm to swim causing infertility.

FertilitySmarts explains Seminal Plasma

Semen contains an average of 2-6 milliliters of seminal plasma per ejaculate. About 75% of seminal plasma is produced by the seminal vesicles, which are 2 glands located behind the bladder. This is rich in fructose and has an alkaline pH. Nearly 20% of the seminal plasma is produced by the prostate gland and it is slightly acidic. The testis and bulbourethral glands, another pair of glands in the male reproductive tract, also have a minor contribution to seminal plasma. After mixing of these fluids, the seminal plasma remains slightly alkaline with a pH ranging from 7.2-8.0.

Constituents of the seminal plasma include sugars (mainly fructose), proteins, enzymes, oxygen and Irons (magnesium, potassium, sulfate, phosphate, bicarbonate). They provide the ideal environment for sperm cells to nourish and protect the sperm from outside stresses.

The vaginal fluid is acidic, which can be toxic to sperm cells. The alkaline medium in seminal plasma neutralizes this acid and makes the environment suitable for sperm cells to survive. After the ejaculate enters the vagina, a chemical reaction develops in the seminal plasma that clumps the ejaculate to form a deposit of sperm cells. This clumping prevents sperm from immediately being exposed to vaginal acids. The clump gradually dissolves after about 20 minutes due to the action of enzymes in seminal plasma allowing sperm to mobilize and start their journey.

Testing the quantity and quality of seminal plasma is required when evaluating a male with infertility. A routine semen analysis looks for the volume of seminal plasma, the appearance, and consistency and if required, the chemical composition.

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