Lecture Notes: Male Reproductive Anatomy and Physiology

Key Anatomical Structures

• Corpora Cavernosa and Corpus Spongiosum: These are the three main erectile tissues in the penis.
  • Sinuses: Small cavities that fill with blood to facilitate erection.
• Veins and Arteries:
  • Dorsal Vein (Subcutaneous and Deep)
  • Dorsal Arteries
  • Deep Arteries: Blood enters through these to fill the sinuses.
• Tunica Albuginea: Connective tissue surrounding the erectile tissues.
• Glands Penis: The enlarged end of the corpus spongiosum.
• External Urethral Orifice: Opening at the glans, often covered by the prepuce (foreskin).

Mechanism of Erection

• Blood fills sinuses in erectile tissues via deep arteries.
• Veins are compressed, preventing blood from leaving, thus sustaining erection.

Penile Fracture

• Occurs due to trauma, often during vigorous sex.
• Results in rupture of the tunica albuginea.
• Immediate medical care required to prevent complications like deformity or urinary problems.

Peyronie’s Disease

• Formation of fibrous plaque in erectile tissue.
• Causes curvature of the penis, which may affect urination and sexual function.

Circumcision

• Removal of the prepuce (foreskin).
• Common in the US, less so elsewhere.
• Pros: Reduced risk of urinary infections, STIs.
• Cons: Decreased sensitivity, potential decrease in sexual pleasure.

Penile Implants

• Used for erectile dysfunction patients who cannot take medication.
• Types:
  • Rod Implant: Rigid, semi-permanent erection.
  • Pump Implant: Inflatable, controlled via a pump in the scrotum.

Muscles and Reflexes in Ejaculation

• Muscles: Ischiocavernosus and bulbospongiosus muscles around the penile root.
• Reflexes:
  • Parasympathetic: Facilitates erection via increased blood flow.
  • Sympathetic: Controls ejaculation, involving muscle contractions and preventing urination.

Ejaculation and Semen Propulsion

• Ejaculation involves peristaltic contractions through the male reproductive tract.
• Pathway: Vas deferens → Seminal Vesicles → Ejaculatory Ducts → Prostate → Penis.

Goals and Key Terms

• Flow of Sperm and Seminal Fluid Composition: Understand the movement and composition of semen, including contributions from seminal vesicles, prostate, and bulbourethral glands.
• Definitions:
  • Prepuce, Circumcision, Erection, Ejaculation, Vasectomy
  • Prostate Gland, PSA, Prostatitis, Peyronie’s Disease, Penile Implant, Penile Fracture
• Muscles Involved in Ejaculation: Identify the key muscles.
• Sperm Coagulation and Liquefaction: Understand why these processes are crucial post-ejaculation.
• Sympathetic vs Parasympathetic Responses: Differentiate between the responses controlling erection and ejaculation.