CS WK7- CH 19 & 28 PROSTATE GLAND, SEMINAL VESICILES, SCROTAL & PENILE SONOGRAPHY

Overview of the Male Pelvis and Accessory Organs

  • The male pelvis comprises various structures, including the prostate, seminal vesicles, and ductus deferens.

The Prostate Gland

  • Definition: The prostate gland is an accessory organ of the male reproductive system.

  • Role: It secretes an alkaline fluid that enhances sperm viability but does not produce sperm directly.

Anatomy of the Prostate

  • Shape: Cone-shaped and located inferior to the urinary bladder.

  • Dimensions: Approximately 4 cm wide, 3 cm anteroposteriorly, and 3.8 cm in length; weighs about 20 grams.

  • Structure:

    • Apex: Inferior margin providing exit for the urethra.

    • Base: Superior aspect in contact with the bladder.

Clinical Significance

  • PSA Levels: Normal serum prostatic-specific antigen (PSA) levels are less than 4. Elevated levels may indicate disease, but are not specific to cancer.

  • Imaging: If PSA is elevated, an MRI is performed to evaluate the prostate; some insurance companies may require an ultrasound first.

    • Ultrasound Limitations: Limited visibility unless transrectal approach is used.

  • Symptoms of Enlarged Prostate: Frequent urination may arise from the prostate pushing against the bladder discharge.

Prostate Changes with Age

  • The prostate typically enlarges benignly as men age. It can also indicate potential issues like infection or malignancy.

Prostate Location and Relations

  • Seated posterior to the pubic symphysis, separated by two layers of tissue known as Denonvilliers fascia.

  • Supported by levator ani and obturator internus muscles.

Seminal Vesicles

  • Definition: Paired glands that contribute to semen production.

  • Function: Produce alkaline viscous fluid and fructose, comprising about 60% of semen volume.

    • They empty into the distal ductus deferens to form the ejaculatory ducts.

Position

  • Located posterior to the bladder and superior to the prostate. Medial to the ureters.

Semen Composition

  • Total composition includes:

    • 60% alkaline fructose (from seminal vesicles)

    • 13-33% alkaline fluid (from prostate)

    • Sperm

Imaging the Prostate

  • Generally assessed for size and echotexture. Commonly appears as low to medium level echoes on ultrasound, medium echos are identifiable on imaging.

    • Measurement: AP and width at right angles for an accurate size estimation. Can include volume calculation via dual-screen imaging.

  • Transrectal Approach: Typically preferred for better visibility of the prostate and seminal vesicles.

Prostate Zones

  • Glandular Structure: The prostate consists of two main regions:

    • Anterior: Fibromuscular region (stroma)

    • Posterior: Glandular region, holds most pathology.

  • Four Zones:

    • Peripheral Zone: Largest, around 70% of prostate gland; demonstrates most imaging and pathology.

    • Transition Zone: Has two lobes near the proximal urethra.

    • Central Zone: Smallest and located posteriorly.

    • Periurethral Zone: Surrounds the urethra directly.

Clinical Evaluation

  • Enhanced visualization typically requires MRI, particularly effective for distinguishing zones and viewing malignant changes.

Testicular Anatomy and Function

  • Testes Definition: Primary male reproductive organs responsible for sperm production and testosterone release.

  • Position: Housed in the scrotum, which helps regulate temperature for optimal spermatogenesis.

Anatomy of Testes

  • Size: Generally size of a walnut or chestnut; dimensions approx. 4 cm long and 3 cm in diameter.

  • Layers:

    • Tunica Vaginalis: Consists of visceral and parietal layers; derived from peritoneum.

    • Tunica Albuginea: Thick layer supporting the testis.

    • Tunica Vasculosa: Vascular layer closely associated.

Internal Structure of Testes

  • Lobules and Tubules: Each testis has 250-300 lobules filled with convoluted seminiferous tubules, crucial for spermatogenesis.

  • Cell Types:

    • Sertoli Cells: Support and nourish germ cells.

    • Leydig Cells: Produce testosterone in the interstitium.

Sperm Maturation Journey

  • Sperm travel approximately 7 meters from seminiferous tubules to urinary meatus, taking about 12 days for maturation through the epididymis.

Epididymis Structure

  • Regions: Divided into head, body, and tail, totaling around 6 meters when unraveled.

  • Function: Acts as a biological assembly line for sperm maturation and storage.

  • Connects to ductus deferens via the epididymal tail.

Ductus Deferens

  • Acts as the transport channel for sperm, approximately 45 cm long, leading to the ejaculatory ducts.

  • Passes through the inguinal canal and continues to the pelvic cavity.

Neurovascular Supply

  • Arterial Supply: Testicular arteries arise from the aorta, with venous drainage via the pampiniform plexus.

  • Lymphatic Drainage: Follows arterial pathways to lumbar lymph nodes.

  • Nervous Innervation: Provided through the testicular plexus from the para-abdominal ganglia.

Common Conditions

  • Benign Prostatic Hyperplasia (BPH): Common enlargement due to age, identifiable by digital rectal examination.

  • Prostate Cancer: Usually found in the posterolateral region, diagnosed through examination.

  • Hydrocele: Fluid accumulation in the tunica vaginalis; presents as enlarged testes.

  • Testicular Torsion: Medical emergency characterized by acute testicular pain; requires prompt diagnosis and intervention.

Additional Notes on Testicular Examination

  • Normal testicular ultrasound reveals medium echogenicity, with emphasis on demonstrating blood flow to rule out torsion or pathologies.

Summary

  • This guide provides an in-depth review of the anatomy and physiology of the male reproductive system, focusing on the prostate and testes.

  • Understanding of normal measurements, imaging techniques, and potential clinical issues are essential for proper evaluation and diagnosis in practice.