Bio Reporductive 1

Overview of Sexual Reproduction

• Purpose: Create genetically distinct new individuals.

• Advantages include:

  • Healthier offspring.

  • Diversity in genome associated with well-being.

  • Opportunities to combine novel traits.

Gametes and Zygote Formation

• Gametes: Reproductive cells (sperm in males and eggs in females)

  • Only have one copy of each chromosome (haploid).

• Fertilization: Union of sperm and egg to form a diploid zygote.

• Importance of having two copies to potentially compensate for defective genes.

Male Reproductive Anatomy

• Major Components:

  • Testes: Produce sperm.

    • Contain convoluted tubules for sperm development.

  • Ductus Deferens (Vas Deferens): Transports sperm.

  • Seminal Vesicles: Add seminal fluid containing fructose and alkaline substances.

  • Prostate Gland: Produces secretions that contribute to semen composition.

  • Cowper's (Bulbourethral) Glands: Contribute to semen and lubricate urethra.

Pathway of Sperm

1. Start in seminiferous tubules (location of spermatogenesis).

2. Flow into ret testes.

3. Move to the epididymis (maturation).

4. Enter vas deferens.

5. Join with seminal fluids in ejaculatory duct before exiting through the urethra.

Anatomy and Function of Testes

• Structures of the Testes:

  • Tunica Albuginea: Connective tissue covering;

  • Tunica Vaginalis: Extends from peritoneum, surrounds testes.

  • Spermatic Cord: Contains blood vessels and nerves.

• Dartos Muscle: Regulates temperature by contracting or relaxing.

Spermatogenesis

• Process that produces sperm:

  1. Spermatogonia: Diploid stem cells replicate via mitosis.

  2. Primary Spermatocytes: Differentiate and begin meiosis.

     • Go through Meiosis I: to form secondary spermatocytes.

  3. Secondary Spermatocytes: Enter Meiosis II.

  4. Spermatids: Resulting haploid cells continue to mature into spermatozoa (sperm).

Structure of Sperm

• Components of mature sperm:

  • Head: Contains genetic material and acrosome with enzymes for egg penetration.

  • Midpiece: Contains mitochondria for ATP production.

  • Tail: Flagellum for locomotion.

Hormonal Regulation of Testicular Function

• Gonadotropin-Releasing Hormone (GnRH): From the hypothalamus, stimulates anterior pituitary.

  • Follicle-Stimulating Hormone (FSH): Stimulates sustentacular cells for spermatogenesis.

  • Luteinizing Hormone (LH): Stimulates interstitial cells to produce testosterone.

Negative Feedback Mechanism

• Increased testosterone levels inhibit GnRH and LH production to prevent excess sperm production.

Accessory Glands and Seminal Fluid Composition

• Seminal Vesicles: Secrete alkaline fluid rich in fructose and prostaglandins.

• Prostate Gland: Produces slightly acidic secretions that nourish sperm.

• Bulbourethral Glands: Provide lubrication and neutralize acidity in urethra prior to ejaculation.

Ejaculation Process

• Distinct phases:

  • Emission: Movement of sperm and seminal fluid into the prostatic urethra.

  • Expulsion: Muscle contractions expel semen via spongy urethra.

• Muscles involved include:

  • Bulbospongiosus, Ischiocavernosus, and superficial transverse perineal muscles.

Erection vs. Ejaculation

• Erection: Caused by parasympathetic nervous system; vasodilation of arterioles allows increased blood flow into erectile tissue.

• Ejaculation: Controlled by sympathetic nervous system, involving reflex muscular contractions.