CH 17 -The Reproductive System A&P

Chapter 17: The Reproductive System

17.1 Human Life Cycle

• Introduction to Human Life Cycle

  • Puberty: Sequence of events leading to sexual maturity.

    • Onset for females: ages 11-13.

    • Onset for males: ages 14-16.

    • Reproductive system functionality peaks at the end of puberty.

17.2 Male Reproductive System

• Functions of the Reproductive Organs

  • Gamete (sperm) production and transport.

  • Key Organs:

    • Testes: Produce sperm and male hormones, located in the scrotum.

    • Accessory Ducts:

      • Epididymis, vas deferens, ejaculatory duct, urethra.

    • Accessory Glands:

      • Seminal vesicles, prostate gland, bulbourethral glands (Cowper's glands).

      • Seminal fluid supports sperm during ejaculation.

Male Internal Accessory Organs

• Epididymides

  • Tightly coiled thread-like tube

  • • Lining consists of ciliated pseudostratified columnar epithelium

  • • Stores and supports sperm

  • • Peristaltic contractions move sperm alongas they mature

  • • Once sperm leave the epididymis, they areable to fertilize the egg even though theydon’t “swim” until they enter the vagina

• Vas deferens

  • • Continuation of the epididymis

  • • Lined by pseudostratified columnar epithelium (partly ciliated)

  • • Contained within the spermatic cord: vas deferens, connective tissue, muscle , testicular artery, testicular vein, nerve

  Vas deferens, cont.

  • • Spermatic cord enters the abdominal cavity via the inguinal canal and widens at the ampulla, located at the posterior base of the urinary bladder

  • • The testes descend through the inguinal canal into the scrotum in the fetus

  • • The canal remains weak and can be the site of an inguinal hernia

  • Joins with the duct of a seminal vesicle to form an ejaculatory duct

  • • The ejaculatory duct passes through the prostate gland to join the urethra

  Seminal Vesicles

  • • Lateral to each vas deferens on the posterior bladder wall

  • •Secrete an alkaline fluid that contains fructose (energy for sperm) and prostaglandins (promotes muscular contractions in the female reproductive tract)

  Prostate

  • • Encircles the urethra

  • Secretes an alkaline fluid that helps adjust the pH of seminal fluid and enhances the motility of sperm

  Bulbourethral Glands (Cowper glands)

  • • Inferior to prostate gland

  • • Secrete a mucus-like fluid that lubricates the end of the penis

  • • Neutralizes acidic urine in the urethra

• The Testes:

  • 
    Produce sperm and the male sex hormones

  • Located outside of the abdominal cavitywithin the scrotum – sperm require a lowertemperature to form

  • Testes develop in the abdominal cavity anddescend into the scrotum about twomonths before birth

  • Cryptorchidism – when the testes failto descend; causes infertility

    Anatomy of a Testis

  • Enclosed by a fibrous capsule that extends to form the septa, which divides testis into lobules

  • Each lobule contains one to three seminiferous tubules

  • Seminiferous tubules contain cells that produce sperm

  • Interstitial (Leydig) cells produce androgens (testosterone)

• The Testes:

  Spermatogenesis, cont.

  • • Two types of cells in the seminiferous tubules: germ cells and sustentacular cells

  • • Germ cells – involved in spermatogenesis

  • • Spermatogonia – divide by mitosis toproduce more cells

  • •Primary spermatocytes – contain 92chromatids (diploid – 46 pairs); startmeiosis

  • Germ cells, cont.•

  • Secondary spermatocytes – the result of meiosis I

  • • Contain 46 chromatids (23 pairs)

  • • Spermatids – the result of meiosis II• Haploid

  • Two types of cells in the seminiferous tubules, cont.

  • • Sustentacular (Sertoli) cells –support, nourish, and regulate the development of cells undergoing spermatogenesis

• The Testes:

  Spermatogenesis, cont.

  • • Spermatids mature into spermatozoa (sperm) and are transported to the epididymis

  • • Sperm have three distinct parts:

  • • Head – contains a nucleus covered by the acrosome

  • • Middle piece – contains mitochondria

  • • Tail – provides motility• Sperm typically survive for about 48 hoursin the female reproductive tract

• Spermatogenesis:

  • Process of sperm production in the testes:

    • Involves meiosis for gamete formation.

    • Two types of cells involved: Germ cells and sustentacular cells.

    • Spermatogonia undergo mitosis to generate primary spermatocytes (diploid).

      • Meiosis I results in secondary spermatocytes (haploid).

      • Meiosis II produces spermatids, which mature into spermatozoa.

17.3 Female Reproductive System

• Functions of the Female Reproductive Organs

  • Primary Sex Organs: Ovaries produce ova and female hormones.

  • Accessory Organs: Uterine tubes (transport ova), uterus (embryo development), vagina (birth canal).

  • Vulva (external genitals): Mons pubis, clitoris, labia majora, labia minora.

• Oogenesis:

  • Process of ovum production, involving meiosis.

    • Primary follicle develops through secondary follicle to mature (Graafian) follicle, releasing a secondary oocyte during ovulation.

• If fertilization occurs, meiosis II is completed.

Meiosis

• Reduction divison- chromosome number is reduced from 46 (2n diploid to 23 (n, haploid) - Takes place in the tests of male and the ovaries of female

• Meiosis I: Chromosme number cut it

• Meiosis II: Regular mitosis

• 
  Fertilization results in a zygote, which isdiploid – a combination of the egg’s DNA andthe sperm’s DNA

• Meiosis ensures that fertilization resultsin a diploid cell

• The zygote divides by mitosis• Growth of fetus, child, and adult is bymitosis

Meiosis

Each division has the same stages as mitosis:

• Prophase

• Metaphase

• Anaphase

• Telophase

Meiosis

• Differences between mitosis and meiosis• Mitosis has one cell division, meiosis has two (so meiosis produces four daughter cells)• Mitosis daughter cells are identical to the parent cell; meiosis daughter cells are haploid and genetically different from the parent cell

17.4 Control of Reproduction and STIs

• Contraception Methods:

  • Prescription hormonal methods (pills, injections, etc.).

  • IUDs, diaphragms, and condoms.

  • Surgical methods (vasectomy, tubal ligation).

• Sexually Transmitted Infections (STIs):

  • Various organisms cause STIs; prevention methods include condom usage.

  • Some STIs can cause severe health implications (e.g., HPV leading to cancer).

17.5 Effects of Aging

• Hormone levels decline with age, affecting reproductive systems.

  • Menopause typically occurs ages 45-55 in females.

  • In men, testosterone production declines gradually which may lead to issues like prostate enlargement.

17.6 Homeostasis

• Estrogen:

  • Promotes fat deposition, protein synthesis, and bone health.

• Androgens:

  • Impact muscle structure and enzyme activity in various organs.

• The chapter illustrates the complex interplay between reproductive health, hormonal regulation, and aging, emphasizing knowledge critical for maintaining long-term health and understanding human development.