Lecture on Male Anatomy

Learning Outcomes

• Understand and list basic structures of the human reproductive system.
• Summarize functions and roles of male reproductive structures.
• Describe structures and functions within the male reproductive system for sperm production.
• Explain the composition of semen.

Overview of Male Reproductive System

• Gametes (sperm) produced in the testes.
• Begin learning terms and structures now for familiarity on exams.
• Important image recognition starting from the testicles (in the scrotum) to the ejaculation pathway.

Important Structures

Testes and Scrotum

• Testes housed in the scrotum, fleshy pouch divided into two chambers, each holding one testis.
• Dartos muscle: smooth muscle causing scrotal wrinkling for temperature regulation. Capable of prolonged contraction.
• Cremaster muscle: voluntary striated muscle for short-term contraction to pull testes closer to body.

Layers and Temperature Control

• Tunica albuginea: fibrous capsule surrounding each testis.
• Tunica vaginalis: serous layers reducing friction.
• Proper temperature maintained by dartos and cremaster muscles, vital for sperm development (2°F lower than body temperature).

Seminiferous Tubules and Sperm Production

• Seminiferous tubules: site for spermatogenesis (sperm production).
• Germ cells: stem cells producing sperm.
• Sertoli cells: support and nurture developing sperm.
• Leydig cells: produce testosterone, located in interstitial space.
• Spermatogenesis involves mitosis, meiosis, and spermiogenesis (final maturation).

Spermatogenesis

• Mitosis: proliferation of spermatogonia.
• Meiosis: generates genetic diversity, produces haploid spermatids.
• Spermiogenesis: physical maturation, packaging of sperm for fertilization.
• Requires testosterone-rich microenvironment, blood-testis barrier by tight junctions of Sertoli cells.

Sperm Anatomy

• Regions: head (nucleus & acrosome), middle piece (mitochondria), tail (propulsion).
• Abnormalities in sperm can affect fertility.

Semen Composition

• Sperm + secretions from reproductive glands.
• Ejaculation Pathway: 7Up mnemonic (Seminiferous Tubules, Epididymis, Vas Deferens, Ejaculatory Duct, Urethra, Penis).

Reproductive Glands

Seminal Glands

• Majority of semen volume.
• Secretions contain fructose, prostaglandins, fibrinogen.

Prostate Gland

• Adds prostatic fluid (20-30% of semen), contains seminalplasmin.

Bulbourethral Glands

• Secrete alkaline fluid for lubrication.

Penis Anatomy and Function

• Regions: root, body, glans.
• Erectile tissue (corpora cavernosa and corpus spongiosum) fills with blood during arousal.
• Erection under parasympathetic control.

Clinical Note

• Importance of knowing prostate health, risk of prostate cancer.
• Erectile dysfunction treatments focus on increasing blood flow to erectile tissues.