reproductive systems

  • Reproductive Systems Overview

    • Male and female reproductive systems consist of connected organs and glands.
    • Hormones regulate reproductive processes and secondary sex characteristics.
    • Reproductive organs produce, nurture, and transport sex cells.

  • Meiosis and Sex Cell Production

    • Male sex cells: sperm; Female sex cells: eggs (oocytes).
    • Sex cells carry 1 set of genetic instructions (23 chromosomes), unlike other body cells (46 chromosomes).
    • Fertilization restores genetic information (46 chromosomes).
    • Production through meiosis, which involves two divisions (meiosis I and II).

  • Meiosis Process

    • Prior to meiosis: Chromosome replication results in 2 chromatids.
    • Meiosis I:
    • Homologous pairs separate, resulting in haploid cells (1 set of chromosomes, 2 chromatids).
    • Meiosis II:
    • Chromatids separate, producing haploid cells with single chromatids.

  • First Meiotic Division

    • Four phases:
    • Prophase I: Synapsis and crossing over occur, exchanging genetic material.
    • Metaphase I: Chromosome pairs align randomly on the spindle midline.
    • Anaphase I: Homologous pairs separate; chromosome number is halved.
    • Telophase I: Cell divides into two daughter cells.

  • Second Meiotic Division

    • Similar to mitosis, consisting of four phases:
    • Prophase II: Chromosomes condense and reappear.
    • Metaphase II: Chromosomes attach to spindle fibers.
    • Anaphase II: Centromeres separate, chromatids migrate.
    • Telophase II: Each cell divides, resulting in up to four gametes (in sperm) while eggs mature unevenly.

  • Organs of the Male Reproductive System

    • Functions: Producing sex cells, transporting sperm, synthesizing sex hormones.
    • Primary sex organs: Testes (spermatogenesis and hormone production).
    • Accessory organs include seminal vesicles, prostate gland, and others.

  • Structure of Testes

    • Enclosed by tunica albuginea.
    • Contains lobules with seminiferous tubules (spermatogenic cells) and interstitial cells (produce hormones).

  • Formation of Sperm Cells

    • Sequence: Spermatogonia → primary spermatocytes → secondary spermatocytes → spermatids → spermatozoa.
    • Meiosis combines with spermiogenesis (sperm development) into spermatogenesis.

  • Structure of a Sperm Cell

    • Components:
    • Head: Contains nucleus (23 chromosomes) and acrosome (enzyme cap).
    • Midpiece: Contains mitochondria for ATP.
    • Tail (flagellum): Propels sperm.

  • Internal Accessory Organs

    • Maintain and transport sperm: Epididymides, ductus deferens, ejaculatory ducts, urethra, seminal vesicles, prostate gland, and bulbourethral glands.

  • Semen Composition

    • Contains sperm and secretions from accessory glands.
    • Slightly alkaline (pH = 7.5), averages 120 million sperm/mL.

  • Male Infertility

    • Inability to fertilize oocyte.
    • Causes: Testes not descending, infections, poor-quality sperm, and low sperm counts.
    • No vital signs observable unless significant conditions arise.

  • Hormonal Control of Male Reproductive Function

    • Controlled by hypothalamus, pituitary gland, and testes.
    • GnRH stimulates FSH (stimulates spermatogenesis) and LH (stimulates testosterone production).

  • Female Reproductive System

    • Functions: Produce oocytes, transport eggs to fertilization site, sustain embryo, and produce female sex hormones.
    • Ovaries are primary organs; accessory organs include uterine tubes and uterus.

  • Oogenesis and Menstrual Cycle

    • Oogenesis produces oocytes; begins during fetal development and resumes at puberty.
    • Primary oocytes remain dormant until ovulation, then secondary oocyte and polar bodies are formed.
    • Menstrual cycle involves cyclic changes in the endometrium and ovaries, leading to menstruation if fertilization does not occur.

  • Female Infertility and Menopause

    • Infertility causes include hormonal imbalances and uterine obstructions.
    • Menopause occurs in later life when cycles stop and hormone production decreases, leading to secondary characteristics fading.