Seminal fluid, also known as semen, is a complex mixture of sperm cells and fluids produced by the male reproductive system. It plays a crucial role in reproduction by providing nutrients and a medium for sperm to travel through the female reproductive tract.

What is seminal fluid?

Seminal fluid, (semen, seminal plasma) is the fluid emitted from the male reproductive system during ejaculation. It is composed of sperm cells produced by the testes and a variety of fluids secreted by accessory glands such as the seminal vesicles, prostate gland, and bulbourethral glands. These fluids provide nourishment, support sperm motility, and facilitate the sperm’s journey through the female reproductive tract. Seminal fluid plays a vital role in reproduction by helping to deliver sperm to the egg during fertilization.

Parameteers of normal seminal fluid

The parameters of normal seminal fluid can be assessed through a semen analysis, which evaluates various aspects of the fluid. Key parameters include:

• Volume: Normal semen volume is typically between 1.5 to 5.0 milliliters per ejaculation.
• Sperm Concentration: Normal sperm concentration is generally greater than 15 million sperm per milliliter.
• Total Sperm Count: A healthy total sperm count is usually greater than 39 million sperm per ejaculate.
• Sperm Motility: At least 40% of sperm should be motile (moving).
• Sperm Morphology: A normal sperm morphology rate is typically greater than 4% of sperm with a normal shape, as assessed by specific criteria.
• pH: Seminal fluid should have a slightly alkaline pH, typically between 7.2 and 8.0.
• Viscosity: Semen should be relatively viscous but should liquefy within 20-30 minutes after ejaculation.
• White Blood Cells: Normally, the presence of white blood cells should be minimal, as an excess may indicate infection or inflammation.

Source of seminal fluid

Seminal fluid is produced by several key structures in the male reproductive system:

• Testes: The testes produce sperm cells and contribute a small amount of fluid to the semen.
• Seminal Vesicles: These glands secrete a significant portion of the seminal fluid. Their secretions include fructose, which provides energy for the sperm, and other substances that help to nourish and support sperm.
• Prostate Gland: The prostate gland produces a fluid that makes up a substantial part of semen. This fluid contains enzymes, such as prostate-specific antigen (PSA), which help to liquefy the semen after ejaculation and support sperm motility.
• Bulbourethral Glands (Cowper’s Glands): These glands secrete a clear, lubricating fluid that helps to neutralize any acidity in the urethra from urine and provides lubrication during ejaculation.

Functions and importance of seminal fluid

Seminal fluid serves several crucial functions and is important for reproductive health:

• Nourishment of Sperm: Seminal fluid provides essential nutrients, such as fructose and proteins, which supply energy to sperm and support their survival and motility.
• Facilitation of Sperm Transport: The fluid acts as a medium that allows sperm to travel through the female reproductive tract. Its viscosity helps to propel sperm and protect them as they move.
• Protection of Sperm: Seminal fluid helps to shield sperm from the acidic environment of the female vagina. It contains substances that buffer and neutralize acidity, which could otherwise damage sperm.
• Enhancement of Sperm Motility: The enzymes and substances in seminal fluid assist in the liquefaction of semen after ejaculation, which helps sperm swim more effectively toward the egg.
• Support for Fertilization: Seminal fluid contains prostaglandins and other compounds that may influence the female reproductive system, such as promoting cervical mucus changes to facilitate sperm entry.
• Lubrication: The fluid helps to lubricate the urethra and the vaginal canal during intercourse, reducing friction and discomfort.

Disorders affect seminal fluid

Several disorders can affect the composition and function of seminal fluid, potentially impacting male fertility. Some common conditions include:

• Oligospermia
• Azoospermia
• Aspermia:
• Low seminal fluid volum
• Hypospermia
• Seminal fluid infections
• Abnormal seminal fluid pH
• Seminal fluid viscosity ıssues
• Sperm morphology abnormalities
• Genetic or hormonal disorders

Differences between seminal fluid and sperm

Seminal fluid and sperm are distinct components of the ejaculate, each with different roles:

Seminal Fluid

• Composition: Seminal fluid is a complex mixture composed of sperm cells, fluids from the seminal vesicles, prostate gland, and bulbourethral glands, along with enzymes, hormones, and other substances.
• Function: Its primary roles are to nourish and support sperm, facilitate sperm transport through the female reproductive tract, protect sperm from the acidic environment of the vagina, and provide lubrication during intercourse.
• Volume: Seminal fluid constitutes the majority of the ejaculate volume, typically ranging from 1.5 to 5.0 milliliters per ejaculation.

Sperm

• Composition: Sperm are individual reproductive cells produced in the testes. Each sperm cell consists of a head (containing genetic material), a midpiece (providing energy), and a tail (enabling movement).
• Function: The primary role of sperm is to carry genetic material from the male to the female egg for fertilization. Sperm are motile and designed to swim through the seminal fluid to reach and fertilize the egg.
• Quantity: Sperm are a smaller component of the ejaculate. In a typical semen sample, the sperm concentration should be greater than 15 million sperm per milliliter.

Differences between seminal fluid and preejaculation urethral fluid

Seminal fluid and preejaculation urethral fluid are both secretions from the male reproductive system, but they have distinct characteristics and functions:

Seminal Fluid

• Composition: Seminal fluid, or semen, is a complex mixture containing sperm cells, fluids from the seminal vesicles, prostate gland, and bulbourethral glands, along with various enzymes, hormones, and other substances.
• Volume: Seminal fluid is the primary component of ejaculate, typically ranging from 1.5 to 5.0 milliliters per ejaculation.
• Function: It provides nourishment and support for sperm, facilitates sperm transport through the female reproductive tract, protects sperm from acidic environments, and provides lubrication during intercourse.
• Ejaculation: Seminal fluid is released during ejaculation and contains sperm cells.

Preejaculation Urethral Fluid

• Composition: Preejaculatory fluid, also known as pre-cum, is a clear, lubricating fluid secreted by the bulbourethral glands (Cowper’s glands). It contains mucus and a small amount of enzymes but does not typically contain sperm.
• Volume: The volume of preejaculatory fluid is much smaller compared to seminal fluid, and its release occurs before ejaculation.
• Function: Preejaculatory fluid lubricates the urethra and neutralizes any acidity from residual urine, providing a more favorable environment for sperm during ejaculation. It also helps to prepare the urethra for the passage of semen.
• Ejaculation: It is released during sexual arousal before ejaculation, and while it may contain trace amounts of sperm if sperm from a previous ejaculation are present in the urethra, it typically has a low sperm concentration.

Diseases affect seminal fluid

Several organ diseases can affect the composition and quality of seminal fluid. Here’s how diseases of specific organs impact seminal fluid:

• Prostate diseases: Prostatitis, Benign Prostatic Hyperplasia (BPH), Prostate Cancer:
  • Seminal vesicle disorders: Seminal vesiculitis, cysts or tumors:
  • Testicular disorders: testicular cancer, orchitis
  • Bulbourethral gland disorders: Infections or Inflammation,
  • Hormonal Disorders: hypogonadism, endocrine disorders
  • Systemic conditions: diabetes, chronic kidney disease

Summary

Seminal fluid, or semen, is a complex mixture produced by the male reproductive system. It consists of sperm cells from the testes and secretions from the seminal vesicles, prostate gland, and bulbourethral glands. Seminal fluid plays a crucial role in reproduction by ensuring sperm viability and facilitating successful fertilization.

Prof. Dr. Emin ÖZBEK

Urologist

Istanbul- TURKIYE