Reproductive Systems

General Outcomes

  • Survival of human species ensured through reproduction.

  • Human reproduction regulated by chemical control systems.

  • Cell differentiation and development regulated by genetic, endocrine, and environmental factors.

Unit Contents

  • Chapter 14: The Continuance of Human Life.

  • Chapter 15: Human Development.

Focussing Questions

  • How does a human change from conception through life stages?

  • What roles do chemical control systems play in regulating human reproduction?

  • How do reproductive technologies challenge societal options, assumptions, and beliefs?

Preparation

  • The endocrine system consists of glands and tissues that secrete hormones.

  • Hormones are chemical signals affecting other glands or tissues.

  • The endocrine system interacts with the nervous system to maintain homeostasis.

  • Table P6.1 reviews principal endocrine glands and some of their hormones.

  • Figure P6.1 reviews hormones of the pituitary gland.

  • Oxytocin, prolactin, hGH, FSH, and LH play roles in reproductive organ development and new human life.

Principal Endocrine Glands and Hormones:

  • Hypothalamus: Releasing and inhibiting hormones regulate anterior pituitary hormones.

  • Anterior Pituitary:

    • hGH: Stimulates cell division, bone and muscle growth, and metabolic functions.

    • TSH: Stimulates the thyroid gland.

    • ACTH: Stimulates the adrenal cortex to secrete glucocorticoids.

    • FSH: Stimulates production of ova and sperm.

    • LH: Stimulates sex hormone production.

    • PRL: Stimulates milk production.

  • Posterior Pituitary:

    • ADH: Promotes water retention by the kidneys.

    • OCT: Stimulates uterine contractions and milk release.

  • Thyroid:

    • Thyroxine (T4): Increases metabolic rate and regulates growth.

    • Calcitonin: Lowers blood calcium levels.

  • Parathyroid:

    • PTH: Raises blood calcium levels.

  • Adrenal Cortex:

    • Glucocorticoids: Raise blood glucose and break down protein.

    • Mineralocorticoids: Promote sodium and water reabsorption.

    • Gonadocorticoids: Promote secondary sexual characteristics.

  • Adrenal Medulla:

    • Epinephrine and norepinephrine: Fight-or-flight hormones raise blood glucose.

  • Pancreas:

    • Insulin: Lowers blood glucose and promotes glycogen formation.

    • Glucagon: Raises blood glucose by converting glycogen to glucose.

  • Ovaries:

    • Estrogen: Stimulates uterine lining growth and development of female secondary sexual characteristics.

    • Progesterone: Promotes uterine lining growth and prevents contractions.

  • Testes:

    • Testosterone: Promotes sperm formation and development of male secondary sexual characteristics.

Key Concepts

  • Sperm-egg contact is central to human reproduction, creating a single cell that develops into a human.

  • Humans can mate and produce young at any time of year which contributes to population adaptability.

Chapter Concepts

  • 14.1: Male and Female Reproductive Systems

    • Systems share common features but also have distinct differences.

    • Gametes are sperm in males and eggs (ova) in females.

  • 14.2: Effect of Sexually Transmitted Infections (STIs) on Reproductive Systems

    • STIs may be caused by bacteria and viruses.

    • STIs can harm individuals' health and interfere with egg and sperm function.

  • 14.3: Hormonal Regulation of the Reproductive Systems

    • Hormonal and genetic factors affect gonad and reproductive organ formation during prenatal development.

    • Sex hormones maintain the function of male and female reproductive systems.

14.1 The Male and Female Reproductive Systems

  • Male and female reproductive systems unite reproductive cells.

  • Both systems include gonads (testes and ovaries) that produce gametes (sperm and eggs).

  • Gonads produce sex hormones that control reproductive system function.

  • Primary sex characteristics: organs, ducts, and glands directly involved in reproduction.

  • Secondary sex characteristics: distinct features not directly related to reproductive function.

Male Reproductive System

  • Produces and stores sperm cells.

  • Deposits sperm cells within the female reproductive tract.

  • Structures located inside and outside the body.

Testes

  • Male gonads held outside the body in the scrotum.

  • Scrotum regulates testes temperature (sperm production best at ~35°C).

  • Composed of seminiferous tubules (sperm production) and interstitial cells (testosterone secretion).

  • Each testis contains over 250 m of seminiferous tubules, producing over 100 million sperm daily.

  • Mature sperm: tadpole-shaped, ~0.06 mm long, with head (nucleus and acrosome), middle piece (mitochondria), and tail (motility).

  • Sertoli cells support and nourish developing sperm.

  • Sperm transported to epididymis for maturation, then to ductus deferens leading to ejaculatory duct and penis.

Penis

  • Male organ for sexual intercourse.

  • Transfers sperm to female reproductive tract.

  • Shaft with glans penis, covered by foreskin.

  • During arousal, increased blood flow causes erection.

Seminal Fluid

  • Sperm mixes with fluids from seminal vesicles (fructose), prostate gland, and Cowper’s gland (alkaline fluid).

  • Combination called semen.

  • Semen enters urethra; ejaculation results from interactions between nervous systems.

Female Reproductive System

  • Ovaries produce a limited number of gametes (ova).

  • Provides a safe environment for fertilization, development, and birth.

Ovaries

  • Suspended by ligaments in the abdominal cavity.

  • Site of oogenesis (ovum production).

  • Usually, only one ovary produces an egg each month.

  • Follicles contain developing ova.

  • Ovulation: follicle ruptures, releasing ovum into oviduct.

  • Fimbriae sweep ovum into oviduct (Fallopian tube).

Uterus and Vagina

  • Uterus: muscular organ holding and nourishing fetus.

  • Endometrium: uterine lining rich in blood vessels.

  • Cervix: narrow opening connecting uterus to vagina.

  • Vagina: entrance for sperm, exit for fetus during childbirth.

  • Ovum survives up to 24 hours; fertilization may occur in oviduct.

  • Zygote moves to uterus, implants in endometrium for development.

  • If no fertilization, endometrium disintegrates (menstruation).

  • Vulva: female external genital organs.

Differences between Sperm Cells and Egg Cells:

  • Size: \textrm{Egg cell >> Sperm cell}

  • Energy reserves: Egg \sim 140,000 mitochondria while sperm \sim 50-100 mitochondria

  • Numbers produced: \[0.1cm]Sperm:
    \geq 300 million a day in a males lifetime, Egg: usually 1 a month, total of 400-500 eggs.

  • Motility: Sperm are motile, eggs are not.

  • Outer structures: sperm head has acrosome containing enzymes to enter egg. Egg is covered by thick membrane.

Section 14.1 Summary

  • fertilization is gamete fusion

  • male: produce large amounts of sperm

  • sperm produced in seminiferous tubules, matures in epididymis

  • Arousal causes sperm to go the vans deferens and semen is produced.

  • Female: produce small numbers of ova in follicles of the ovary which may be fertilized in the oviduct
    *Zygote implants in uterus or there is menstruation

14.2 Sexually Transmitted Infections (STIs)

  • Infections transmitted through sexual contact.

  • Caused by viruses, bacteria, and parasites.

Common STIs

  • Viral: HIV/AIDS, hepatitis, genital herpes, HPV.

  • Bacterial: Chlamydia, gonorrhea, syphilis.

HIV/AIDS

  • AIDS caused by HIV, which attacks helper T cells.

  • Transmitted through sexual contact, shared needles, or from mother to child.

  • No cure; treatments alleviate symptoms.

Hepatitis

  • Hepatitis A: contaminated water, oral/anal contact.

  • Hepatitis B: sexual contact, infected fluids/blood (STI).

  • Hepatitis C: blood-to-blood contact (needles).

  • Vaccines available for hepatitis A and B.

  • Can cause liver failure, cancer, and death.

Genital Herpes

  • Caused by herpes simplex viruses (HSV 1 or HSV 2).

  • Symptoms: tingling/itching, blisters, painful sores.

  • No cure; antiviral medication can control outbreaks.

  • Risk of transmission to baby during birth.

Human Papilloma Virus (HPV)

  • Causes genital warts, transmitted by skin-to-skin contact.

  • May be asymptomatic.

  • Linked to cervical cancer and other tumors.

Chlamydia

  • Bacterial STI, often asymptomatic.

  • Can lead to pelvic inflammatory disease (PID) in women.

  • Treated with antibiotics.

Gonorrhea

  • Bacterial STI caused by Neisseria gonorrhoeae.

  • Can infect urethra, cervix, rectum, and throat.

  • Treated with antibiotics.

Syphilis

  • Bacterial STI caused by Treponema pallidum.

  • Progresses in three stages with periods of latency.

  • Treated eith antibiotics

Section 14.2 Summary

  • Education+ safe sex important
    *STI's caused by viral or bacterial infection: HIV, hepatitis, herpes, HPV, chlamydia, gonorrhea, syphilis
    *May show no symptoms but spread regardless

14.3 Hormonal Regulation of the Reproductive System

  • Chromosomal sex (XX or XY) determined at fertilization.

  • Hormones determine sex organ development, maturation, and function.

Sex Hormones

  • Androgens (male sex hormones).

  • Estrogen and progesterone (female sex hormones).

Male Reproductive System

  • Testis-determining factor (TDF) gene on Y chromosome triggers androgen production.

  • Androgens initiate development of male sex organs and ducts.

  • Puberty: hypothalamus increases GnRH production, leading to FSH and LH release.

  • FSH and LH cause testes to produce sperm and testosterone.

  • Hormone feedback mechanisms control spermatogenesis and maintain secondary sexual characteristics.

Aging and the Male Reproductive System

  • Most men experience a gradual decline in testosterone around age 40 (andropause).

  • Prostate gland may enlarge, leading to urinary difficulties.

Female Reproductive System

  • Hypothalamus increases GnRH production at puberty.

  • This leads to FSH and LH release.

  • FSH and LH act on ovaries to produce estrogen and progesterone.

Hormonal Regulation of the Female Reproductive System

  • Menstrual cycle: ensures ovum release when the uterus is receptive.

  • Ovarian cycle: includes follicular and luteal stages.

  • Uterine cycle: prepares uterus for implantation.

Aging and the Menstrual Cycle

  • Number of functioning follicles decreases, leading to menopause.

  • Menopause: end of the menstrual cycle.

  • Hormone replacement therapy (HRT) may be considered but has health risks.

Section 14.3 Summary
*Gonands produce testosterone or estrogen/ progesterone
*FSH and LIH trigger gametes and release of sex hormones resulting in puberty
*Hormone systems interact to regular monthly mentrual cycle in females

Comparing sex hormones

Testosterone: development of male sex organs, male features like hair everywhere
Estrogen: development of female organs, menstruation cycle