What is Seminal Plasma? – 2 Important Functions and Research

What is Seminal Plasma?

Seminal plasma is a complex fluid made up of secretions from the seminal tract’s organs and tubules (bulbourethral glands, seminal vesicles, prostate, vasa deferentia, and epididymides) as well as the testicles’ seminiferous tubules.

The function of seminal plasma is

  1. It acts as a carrier, protector, and nourishment medium for spermatozoa from ejaculation until fertilization, as well as a functional regulator of spermatozoa function.
  2. Furthermore, seminal fluid contact during conception helps to activate endometrial gene expression and immune cell modifications that are necessary for successful implantation, affecting not only the quality of the subsequent pregnancy but also the health of the offspring.
Seminal Plasma
Fig1: Sperm in Microscopy

Composition of Seminal Plasma

Despite species-specific anatomical differences, it contains inorganic ions, particular hormones, proteins, and peptides, including cytokines and enzymes, cholesterol, DNA, and RNA, the latter of which is frequently preserved within epididymis- or prostate-derived extracellular vesicles.

Water, proteins, fructose, cholesterol, citric acid, ascorbic acid, lactic acid, minerals, vitamin B12, blood group antigens, nitrogen, and uric acid are the main components of sperm.

Albumin and free amino acids make up the majority of the semen, accounting for around half of it. Fertility is determined by the amount of fructose in the sperm. Catecholamines like adrenaline, noradrenaline, and dopamine are also found in sperm. Catecholamines play a role in sperm count, sperm motility, and overall fertility.

Seminal plasma
Fig 2: Origin, Composition, and Function of seminal plasma

What is Seminal Fluid or Semen?

Semen also known as Seminal plasma transports, protects, and nourishes spermatozoa following the ejaculation procedure for fertilization. Semen is made up of sperm and seminal plasma.

Sperm: Sperm cells comprise three parts: a head, a midpiece, and a tail.

Seminal Plasma

Seminal plasma which is the fluid part of semen is formed by the Seminal vesicles, the prostate gland, and the bulbourethral glands. Seminal vesicles secrete fructose, citric acid, and additional nutrients.

By secreting fibrinogen and prostaglandin, the seminal vesicle also helps. The prostate gland, which secretes calcium and phosphate ions, provides alkalinity.

Though sperm constitute the most essential biological component of sperm, semen also contains several other vital components. Semen gives sperms food and gives them a place to swim.

Ejaculation is the procedure through which males discharge their sperm. Sperm are combined with diverse secretary fluids from the seminal vesicles, prostate, and bulbourethral glands as they move through the ejaculatory channels. The semen is made up of these fluids as well as the sperms.

The seminal vesicles create a yellowish, sticky fluid. It contains a lot of fructose. 70 percent of the entire volume of the semen is made up of fluid from the seminal vesicles. Prostate glands generate a yellowish, thin fluid containing proteolytic enzymes, lipids, citric acid, and phosphatase.

It accounts for 25–30% of the total volume of sperm. To lubricate the urethral lumen, the bulbourethral glands create a whitish fluid. This fluid accounts for about 1% of the total volume of sperm. In humans, each ejaculation releases between 200 and 500 million sperm.

Sperm make up 2–5% of the total volume of the sperm. Humans ejaculate about 3.4 mL of semen per ejaculation. The semen is a whitish-gray hue. Due to the presence of sperm, the semen displays an opalescent look.

Seminal plasma
Fig 3: Production to Maturation of Sperm

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A male reproductive cell is referred to as sperm. Sperms are small, compact cells that have evolved to perform a specific task: fertilizing the female egg cell. 

Beginning in adolescence, males continue to create sperm cells throughout their lives. Sperm are created in the gonads through a process known as spermatogenesis. Primary spermatocytes are diploid, producing four mature sperm cells or spermatozoa per cell.

The head, middle region, and tail are the three components of a normal sperm cell. A haploid nucleus, a pair of centrioles, and an acrosome cap make up the head. The haploid nucleus has a single set of the species’ chromosomes. There are 23 chromosomes in a human sperm nucleus.

The acrosome cap contains hydrolytic enzymes that aid in penetrating the egg cell’s jelly layer. The central region of the sperm contains a considerable number of mitochondria. They generate the energy required for the tail’s motion. In humans, the tail is made up of a single flagellum.

Fig 4: Spermatozoa

Research on Seminal Plasma

The Seminal plasma is undeniably involved in a variety of elements of sperm activity before fertilization. The Seminal plasma also connects with the tubular genital tract’s numerous compartments, causing changes in gene function that prepare the body for a successful pregnancy; as a result, it controls fertility.

Despite these ideas, it’s important to remember that Seminal plasma -free spermatozoa (epididymal or washed ejaculated) are indeed productive, so various studies are going on to understand the differences between the role of seminal plasma in vivo following deposition of spermatozoa on female ova and on that seminal plasma which is used as an addition on spermatozoa used for artificial reproduction and even include cryopreservation, artificial insemination, and even in-vitro fertilization.

Difference Between Semen and Sperm

A male reproductive cellIt is a reproductive fluid in male which consist of sperms in suspension.
Produced by plants and animalsProduced by male animals and hermaphrodites
Produced by spermatozoa in the testesCollection of fluid produced by seminal vesicles, prostate glands, and bulbourethral glands
A microscopic cell consisting of an oval-shaped head, small neck, and a long tailWhitish gray-colored viscous liquid
The cellular component of semenCombination of cellular components and seminal plasma
Carries genetic information of a male to an egg cell of the same species for fertilizationNourish the sperms carries them by maintaining their mobility and viability
Microscopic featuresVisible with the naked eye
Difference between Semen and Sperm

From where seminal plasma is released and stored?

The fluid element of semen, seminal plasma, is released by both the epididymis and the accessory glands before and during ejaculation. Seminal plasma is a complicated fluid that acts as a vehicle for delivering ejaculated spermatozoa from the testes to their intended destination, the oocyte.

Are there any enzymes present in seminal plasma?

Superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase are enzymatic ROS scavengers found in seminal plasma (CAT). These enzymes are antioxidants and lipid peroxidation inhibitors

What are the most important elements in seminal plasma?

Mucus, spermatozoa, and different secretions of accessory glands are the main components of seminal plasma in the male reproductive system. Fructose, calcium, ascorbic acid, and some enzymes are abundant in seminal plasma. They act as sperm nutrients and help in protection.

Why are mitochondria found in sperm?

The acrosome, which is located at the tip of the sperm head, allows the sperm to penetrate the egg. The mitochondria that lie in the midpiece are responsible for providing the energy required for tail mobility. To drive the sperm towards the egg, the tail makes whip-like movements back and forth.

What is the significance of acrosome?

The acrosome is a cap-like covering that covers the oval-shaped head of normal sperm cells. The acrosome contains enzymes that tear down an egg cell’s outer membrane, allowing sperm to fertilize it.

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