Skip to main content
Back

42 patho

NotesPracticeVideo lessons

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Structure and Function of the Male Genitourinary System

Accessory Organs and Composition of Semen

The male genitourinary system includes several accessory organs that contribute to the formation and function of semen, which is essential for reproduction.

  • Seminal Vesicles: Produce fluid that nourishes sperm and helps form semen.

  • Prostate Gland:

    • Adds secretions that protect and enhance sperm mobility.

    • Provides the majority of fluid found in semen.

  • Bulbourethral (Cowper's) Glands: Secrete mucus to lubricate and neutralize acidity in the urethra before ejaculation.

Spermatogenesis

Spermatogenesis is the process by which sperm cells (spermatozoa) are produced in the male reproductive system.

  • Initiation: Begins around age 13 and continues throughout a man's reproductive life.

  • Location: Occurs in the seminiferous tubules of the testes.

  • Gonadotropic Hormones Involved:

    • FSH (Follicle-Stimulating Hormone): Binds to receptors on Sertoli cells to support sperm development.

    • LH (Luteinizing Hormone): Stimulates Leydig cells for the production of testosterone.

  • Testosterone: Required for spermatogenesis; levels are about 100 times higher in the testes than in the blood.

Clinical Note: A lack of testicular enlargement and sparse pubic hair suggests deficiency in FSH and/or LH, leading to low testosterone and poor sperm development.

Male Sex Hormones (Androgens) and Functions of Testosterone

Androgens are male sex hormones that play a crucial role in the development and maintenance of male reproductive functions and secondary sex characteristics.

  • Main Types:

    • Testosterone

    • Dihydrotestosterone (DHT)

    • Androstenedione

  • Functions of Testosterone:

    • Guides the development of male reproductive organs during fetal growth.

    • Promotes primary (testes, penis) and secondary (facial hair, voice changes, muscle growth) sex characteristics at puberty.

    • Has anabolic effects, helping build muscle and bone mass.

  • Anabolic Effects of Testosterone:

    • Helps build proteins in the body.

    • Promotes muscle and bone growth.

    • Affects how fat is distributed under the skin.

    • Supports spermatogenesis and the maturation of sperm.

Hypogonadism

Hypogonadism refers to the low production of sex hormones by the testes or ovaries, resulting in low androgen (testosterone) levels.

  • Testosterone Levels:

    • Normal: 300–1000 ng/dL

    • Deficient: Less than 300 ng/dL

  • Types:

    • Primary: Problem in the testes (testicular failure).

    • Secondary: Problem in the pituitary gland (not sending gonadotropins).

    • Tertiary: Problem in the hypothalamus (not stimulating the pituitary to release hormones).

  • Symptoms: Fatigue, low mood, decreased sex drive, and reduced energy. Effects depend on whether sperm production or testosterone secretion is affected.

Neural Control of the Sex Act

The sexual response in males is regulated by complex neural pathways involving sensory input, autonomic control, and reflexes.

  • Sensory Input: The glans penis has many sensory receptors; signals travel through the pudendal nerve to the spinal cord (sacral plexus).

  • Stimulation: Stimulation of other perineal areas also activates higher brain centers, enhancing sexual response.

  • Erection: Involves blood flow (shunting) into the corpus cavernosum, causing the penis to become firm. Controlled by sympathetic, parasympathetic, and non-sympathetic pathways.

  • Emission and Ejaculation:

    • Emission: Moves sperm from the epididymis to the urethra; mainly controlled by sympathetic reflexes at spinal levels L1–L2.

    • Ejaculation: Triggered by efferent signals from the spinal cord, causing smooth muscle contraction in the vas deferens and ampulla to expel semen.

Effect of Aging on the Male Reproductive System

Aging causes gradual degenerative changes in the male reproductive system, leading to decreased efficiency over time.

  • The decline is slow and progressive, not sudden.

  • Multiple systems are involved:

    • Endocrine system: Lower hormone production (especially testosterone).

    • Circulatory system: Reduced blood flow affects erectile function.

    • Neuromuscular system: Decreased nerve and muscle response.

Diseases Affecting Potency

Several diseases can affect male sexual potency by interfering with the physiological processes required for erection and sexual performance.

  • Cardiovascular Diseases: Reduce blood flow needed for erection.

  • Respiratory Diseases: Lower oxygen levels, decreasing stamina and sexual performance.

  • Hormonal Disorders: Low testosterone or other hormone imbalances affect libido and erection.

  • Neurologic and Blood Disorders: Nerve damage or poor circulation can interfere with erectile function.

Review Questions

  • What is spermatogenesis and when does it begin?

  • What does the prostate do as an accessory organ?

  • What gonadotropic hormones are involved in spermatogenesis and what happens when there is an alteration of these hormones?

  • What is hypogonadism?

  • What diseases affect potency and how do they affect potency?

Pearson Logo

Study Prep