What is the Prostate? Anatomy, Function & Location

What is the prostate? – Basic definition

The prostate is a small, walnut‑sized gland found only in males. It is part of the male reproductive system and sits just below the bladder, surrounding the urethra – the tube that carries urine and semen out of the body.

The prostate grows throughout a man's life, but it can become problematic when it enlarges too much (benign prostatic hyperplasia – BPH) or develops inflammation (prostatitis) or cancer.

Where is the prostate located?

The prostate is located in the pelvis, deep inside the body. Its position is best understood by its surrounding structures:

• Above (superior): Bladder neck (the prostate sits directly under the bladder).
• Below (inferior): Urogenital diaphragm and the external urethral sphincter.
• In front (anterior): Pubic symphysis (pubic bone), separated by the retropubic space.
• Behind (posterior): Rectum – this is why the prostate can be felt during a digital rectal exam (DRE).
• Through the centre: The urethra runs through the prostate (prostatic urethra).

Clinical relevance: Because the urethra passes through the prostate, prostate enlargement can squeeze the urethra, causing urinary symptoms (weak stream, frequency, hesitancy).

What does the prostate do?

The prostate has three main functions:

• Produces seminal fluid: The prostate secretes a milky, alkaline fluid that makes up 20‑30% of semen volume. This fluid contains enzymes (prostate‑specific antigen – PSA), citric acid, zinc, and other nutrients that nourish and protect sperm.
• Helps with ejaculation: During ejaculation, the prostate contracts, pushing its fluid into the urethra, where it mixes with sperm from the vas deferens and fluid from the seminal vesicles.
• Hormonal role: The prostate converts testosterone into its more potent form, dihydrotestosterone (DHT), which stimulates prostate growth.

Without a prostate, men can still ejaculate (semen volume is reduced) but may have fertility issues. The prostate does NOT produce urine or testosterone – common misconceptions.

Normal prostate size by age

The prostate grows throughout life, but the rate of growth increases after age 40. Normal size is measured in grams (g) or volume (mL). On ultrasound, the prostate is roughly 3‑4 cm in length, 4‑5 cm in width, and 2‑3 cm in height.

• Age 20‑30: 15‑20 grams (walnut‑sized).
• Age 30‑40: 20‑25 grams.
• Age 40‑50: 25‑30 grams.
• Age 50‑60: 30‑40 grams (golf ball‑sized).
• Age 60‑70: 40‑50 grams.
• Age 70+: 50‑70 grams or more (tennis ball‑sized).

BPH is typically diagnosed when the prostate exceeds 30‑40 grams and causes symptoms. However, symptom severity does not always correlate with size – some men with very large prostates have mild symptoms, and vice versa.

Prostate anatomy – zones and histology

The prostate is divided into distinct anatomical zones, which have different clinical importance:

• Peripheral zone (PZ): ~70% of glandular tissue. Located posteriorly. Most prostate cancers (70‑80%) arise here. Palpable on DRE.
• Central zone (CZ): ~25% of glandular tissue. Surrounds the ejaculatory ducts. Less common site for cancer.
• Transitional zone (TZ): ~5% of glandular tissue. Surrounds the prostatic urethra. Site of benign prostatic hyperplasia (BPH).
• Anterior fibromuscular stroma (AFMS): Non‑glandular, muscular tissue. Forms the anterior surface. Rarely involved in disease.

Histology: The prostate consists of tubuloalveolar glands lined by two layers of epithelial cells (basal and secretory). The secretory cells produce PSA and prostatic acid phosphatase (PAP).

Blood supply and innervation

Arterial supply: The prostate receives blood from the inferior vesical artery (branch of the internal iliac artery), which gives off prostatic branches. The middle rectal and internal pudendal arteries contribute small branches.

Venous drainage: Prostatic venous plexus drains into the internal iliac veins. This plexus communicates with the vertebral venous plexus (Batson's plexus), which is a route for prostate cancer metastasis to the spine.

Innervation – crucial for erectile function:

• Parasympathetic (pelvic splanchnic nerves, S2‑S4): Controls erection (vasodilation). These nerves run along the posterolateral surface of the prostate as the neurovascular bundles. Injury during prostatectomy causes erectile dysfunction.
• Sympathetic (hypogastric nerves): Controls ejaculation and smooth muscle tone.

Why prostate health matters

The prostate is involved in three major medical conditions that affect millions of men worldwide:

• Benign Prostatic Hyperplasia (BPH): Non‑cancerous enlargement of the prostate, affecting >50% of men over 60. Causes urinary symptoms (frequency, urgency, weak stream, nocturia).
• Prostatitis: Inflammation or infection of the prostate. Acute prostatitis causes fever and severe urinary symptoms; chronic prostatitis (CPPS) causes pelvic pain without infection.
• Prostate cancer: The second most common cancer in men worldwide (after lung cancer). Most prostate cancers are slow‑growing, but some are aggressive. Early detection via PSA screening saves lives.

Understanding what the prostate is and where it is located is the first step toward recognising symptoms and seeking appropriate care.

Common myths about the prostate

• Myth: "Only older men have prostate problems."
  ➜ Fact: Prostatitis can occur at any age, even in young men (20s‑30s). BPH is rare before 40 but can occur earlier.
• Myth: "An enlarged prostate always means cancer."
  ➜ Fact: Most prostate enlargement is benign (BPH). Cancer is only one cause and is less common than BPH.
• Myth: "If you have no symptoms, your prostate is healthy."
  ➜ Fact: Early prostate cancer often has no symptoms. That is why PSA screening is important.
• Myth: "Prostate problems always cause pain."
  ➜ Fact: BPH and early prostate cancer are usually painless. Pain suggests prostatitis or advanced cancer.
• Myth: "The prostate produces urine."
  ➜ Fact: No. The prostate produces seminal fluid. Urine is produced by the kidneys and stored in the bladder.

Interactive FAQ – 9 questions about the prostate

Disclaimer: This information is for educational purposes. If you have prostate symptoms or concerns, consult a urologist at Vivekananda Hospital for proper evaluation and care.