The Prostate: Anatomy and Functions

The prostate is a small gland, but it's central to male physiology. Often ignored until problems arise, it's actually a key organ for fertility, sexuality, and even urination.

Understanding its structure, functions, and potential pathologies is essential to promoting male health, especially as men age.

Where is the prostate located and what does it look like?

The prostate is located in a strategic position and delicate within the male body. It is found in the pelvic cavity, immediately below the bladder and in front of the rectum. This location makes it easily accessible via rectal examination, but also vulnerable to conditions that can affect both urinary and sexual function.

The gland surrounds the initial portion of the urethra, called the prostatic urethra, which is the channel through which urine and seminal fluid are expelled.

It is precisely this “transitional” position that makes the prostate a functional crossroads between the urinary and genital systems.

Its internal structure is divided into anatomical zones, each with specific characteristics and functions.

Transition zone

The transitional zone is a small, rounded portion that constitutes just 5% of the prostate volume in young adults. It envelops preprostatic urethra , that is the portion of the urethra that passes through the prostate before receiving the ejaculatory ducts.

It is completely internal to the gland: anteriorly, it is covered by the anterior fibromuscular stroma, posteriorly it is in contact with the central zone, while laterally and inferiorly it connects to the peripheral zone. It is just anterior to the ejaculatory ducts.

This area is particularly important from a clinical standpoint because it tends to enlarge with age, causing benign prostatic hyperplasia (BPH). The enlargement can compress the urethra and cause urinary problems.

Central zone

The central zone has a shape similar to a truncated cone and represents approximately 25% of the gland's volume. It is traversed along its entire length by the ejaculatory ducts, which run exclusively in this portion of the prostate. Anteriorly, it is connected to the transitional zone, while posteriorly and laterally, it borders the peripheral zone.

Its apex forms the verumontanum, a small protrusion in the prostatic urethra where the ejaculatory ducts open. In this area, just above the transitional urethra and surrounding the preprostatic urethra, are simple mucous glands, not identical to the true prostate glands, which contribute to the production of seminal fluid.

Peripheral zone

The peripheral zone is the largest, constituting approximately 70% of the gland's volume. It is cup-shaped or inverted cone-shaped and partially encloses the preprostatic and prostatic urethra. It contains the transitional zone and is related anteriorly and medially to the central zone, and anteriorly to the fibromuscular stroma.

This area is the most frequently affected by prostate cancerr, which is why it is explored during DRE. Its posterior location makes it accessible and therefore essential for early diagnosis.

Anterior fibromuscular stroma

The anterior fibromuscular stroma is a glandless portion composed of muscle tissue and connective. It occupies the anterior portion of the prostate, enclosing the anterosuperior wall of the preprostatic urethra. Its shape resembles a wedge or an inverted cone. It serves as structural support and is not involved in the production of seminal fluid.

How the prostate changes over time

In terms of size, the prostate resembles a chestnut or an inverted cone. In a young, healthy man, it measures approximately 3-4 cm in length, 4-5 cm in width, and 2-3 cm in thickness, with an average volume of 20-30 cc and a weight of approximately 15-20 grams. However, these dimensions vary over time (read more about dimensions).

During childhood, the prostate is underdeveloped. Its growth accelerates during puberty, under the influence of androgen hormones, particularly testosterone and its active metabolite, the dihydrotestosterone (DHT). It reaches its adult size between the ages of 20 and 30, remaining relatively stable until middle age.

After age 45-50, a physiological process of hyperplasia begins, especially in the transition zone, which can lead to a significant increase in volume. In some men, the prostate can exceed 40 cc. This enlargement is not malignant but can cause bothersome urinary symptoms, such as difficulty starting urination, a weak stream, or the need to urinate frequently, especially at night.

Prostate size changes over time are natural phenomena, but they can become clinically significant and affect quality of life. For this reason, it's advisable to monitor its condition through regular checkups, especially after age 50.

The functions of the prostate

The prostate performs several fundamental functions:

• Production of seminal fluid: prostatic fluid makes up about 25-30% of semen volume. It contains enzymes (such as PSA), zinc and other substances that nourish and protect sperm, improving their motility.
• Ejaculation: during orgasm, the prostate contracts to expel prostatic fluid into the urethra, where it mixes with sperm from the testicles and fluid from the seminal vesicles.
• Urination: the prostate, surrounding the urethra, can affect urinary flow. An enlargement can compress the urethra and cause difficulty urinating.
• Sexuality: although not directly responsible for erection, the prostate contributes to sexual pleasure through contractions during ejaculation.

The main prostatic pathologies

As we age, the prostate can be subject to various conditions:

• Benign prostatic hyperplasia (BPH): is a noncancerous enlargement of the prostate, common after age 50. It can cause urinary symptoms such as a weak stream, frequent urination, nocturia, and a sensation of incomplete emptying.
• Prostatitis: inflammation of the prostate, acute or chronic, which can affect men of all ages, but is most common between the ages of 30 and 50. It causes pelvic pain, burning urination, and painful ejaculation.
• Prostate Cancer: it is the most common cancer in men. It mainly affects people over 50 and can be asymptomatic in the early stages. Early diagnosis is essential and is based on tests such as PSA testing and digital rectal examination.

Reference: https://link.springer.com/chapter/10.1007/978-3-642-84431-7_8