Anatomy and Physiology of the Reproductive System

The Reproductive System

Chapter 27

Lecture Outline
  • Male Reproductive System
    • Anatomy & Physiology
    • Spermatogenesis
  • Female Reproductive System
    • Anatomy & Physiology
    • Oogenesis
    • Ovarian & Uterine Cycles
Male Reproductive System Components
  • Accessory Glands
  • External Genitalia
  • Gonads (testes)
Major Anatomy of Male Reproductive System
  • Pubic Symphysis
  • Urethra
  • Ductus Deferens
  • Penis
  • Epididymis
  • Scrotum
  • Rectum
  • Anus
  • Testis
  • Ureter
  • Urinary Bladder
  • Seminal Gland
  • Prostate Gland
  • Ejaculatory Duct
  • Bulbo-Urethral Gland
Male Gonads: The Testes

  • Structure of Testis

    • Composed of Seminiferous Tubules
    • Contains Epididymis

  • Function of Testes

    • Spermatogenesis: The process of producing sperm.
    • Hormonal Secretion: Secretes testosterone.
    • Sperm Production: Approximately 100-300 million sperm are produced per day.
    • Optimal Temperature for Spermatogenesis: 95ºF
Spermatogenesis
  • Definition: The process of making sperm in the seminiferous tubules.
  • Cell Division Involved:
    • Mitosis
    • Meiosis
  • Duration: Takes approximately 9 weeks to produce a “mature sperm,” referred to as spermatozoon.
Anatomy of Sperm Transport
  • Ductus Deferens, Ejaculatory Duct & Urethra
    • Lined with smooth muscle
    • Transport sperm from testis to the exterior during ejaculation through peristalsis.
Accessory Glands of Male Reproductive System
  • Accessory Glands:
    • Produce seminal fluids which are crucial for reproduction.
    • Seminal Glands: Produce over half of the seminal fluid, aids in capacitating (activating) sperm.
    • Prostate Gland: Produces fluid that neutralizes the acidic vagina, thus enhancing sperm survival.
    • Bulbo-Urethral Glands: Secretes pre-ejaculatory fluid that flushes out residual urine in the urethra (enhancing sperm survival) and acts as a lubricant.
External Genitalia Features

  • Penis:

    • Delivers semen to female reproductive tract and carries urine.
    • Contains vascular tissue that fills with blood during erections.

  • Scrotum:

    • Skin and smooth muscle that encompasses the testes outside the body.
    • Adjusts the position of testes for optimal temperature regarding spermatogenesis.
Hormonal Regulation of Male Reproduction

  • Regulation: Complex interaction of hormones from the hypothalamus, anterior pituitary, and testes.

  • Feedback Mechanisms: Maintain testosterone levels through positive and negative feedback.

  • Hypothalamus: Releases Gonadotropin-Releasing Hormone (GnRH).

    • High testosterone levels inhibit the release of GnRH.
    • GnRH stimulates the anterior lobe of the pituitary gland to release Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH).

  • Inhibin: Produced by nurse cells when stimulated by FSH to regulate FSH and GnRH secretion.

  • LH and FSH Roles:

    • FSH: Targets nurse cells, promoting spermatogenesis and spermiogenesis, and stimulating inhibin secretion.
    • LH: Stimulates interstitial endocrine cells for testosterone secretion.
Spermatogenesis Process including Hormonal Regulation
  1. Mitosis of Spermatogonium (diploid)
  2. Meiosis I: Produces primary spermatocyte (diploid)
  3. Primary Spermatocyte undergoes Meiosis II: Finally results in haploid spermatids.
  4. Spermiogenesis: Physical maturation of spermatids into sperm.
Female Reproductive System
  • Internal Organs Include: Ovaries, Uterine Tubes, Uterus, Cervix, Vagina
  • Gonads: Ovaries
    • Function: Produce eggs (oogenesis) and secrete hormones estrogen and progesterone.
Oogenesis
  • Definition: The process of making eggs in the ovaries.
  • Cell Division: Involves both mitosis and meiosis.
  • Timing: Begins before birth and finishes after fertilization.
  • Comparison: Fewer eggs are produced than sperm.
Internal Organs of Female Reproductive System
  • Uterine Tubes:
    • Collect the oocyte after ovulation and transport it to the uterus.
    • Fimbriae: Finger-like projections that help guide the oocyte.
    • Cilia lining help in drawing the oocyte into the tubes.
  • Uterus:
    • Site of fetal development, with the myometrium assisting in childbirth and shedding during menses.
    • Endometrium: Inner lining grows and sheds in a monthly cycle (menstrual cycle).
  • Cervix: Inferior portion surrounding the cervical canal.
  • Vagina:
    • Distal end of birth canal; serves multiple functions during menses and sexual reproduction.
External Genitalia Features of Female Reproductive System
  • Vulva: Area containing the external genitalia including labia and clitoris.
    • Labia: Protect the vaginal opening and clitoris (analogous to scrotum).
    • Clitoris: Erectile tissue (similar to penis).
    • Vestibular Glands: Secrete mucus for lubrication (analogous to bulbourethral glands).
The Ovarian Cycle
  • Occurs in females after puberty with estrogen from developing follicles.
  • Typically, one follicle completes development monthly; elevated estrogen leads to LH surge necessary for ovulation.
Ovulation Process
  • Occurs when the secondary oocyte bursts out of the ovary into the pelvic cavity due to the follicular wall rupture.
Hormonal Regulation of Female Reproduction

  • Coordination: Necessary between ovarian and uterine cycles to prevent infertility.

  • Regulated by GnRH from the hypothalamus, which fluctuates throughout the ovarian cycle.

  • Follicular Phase: Begins with FSH stimulating follicle growth and development. Elevated estrogen leads to LH surge and ovulation.

  • Luteal Phase Events: Post ovulation follicle forms corpus luteum that secretes progesterone to prepare the uterus and inhibit future GnRH.

Summary of Hormonal Interactions
  1. Follicular Phase:
    • Estrogen peaks, stimulating LH for ovulation.
    • FSH aids in developing follicles.
  2. Luteal Phase:
    • Corpus luteum secretes progesterone and impacts endometrial thickness and secretions.
  3. Temperature Changes: Basal body temperature varies between follicular & luteal phases, influenced by hormonal changes.
Phases of the Uterine Cycle
  1. Menstrual Phase: Occurs when estrogen levels are low, leading to shedding.
  2. Proliferative Phase: Endometrium regeneration due to rising estrogen levels.
  3. Secretory Phase: Thickening of endometrium with nutrient secretion under progesterone influence.
Conclusion
  • The interplay of hormones ensures the reproductive system functions properly. Disruption can lead to infertility, highlighting the need for balanced hormonal regulation across both systems.