Sexual Reproduction

SEXUAL REPRODUCTION

Overview of Sexual Reproduction

  • Egg (Ovum):

    • Contains 23 Chromosomes.

  • Sperm:

    • Contains 23 Chromosomes.

  • Fertilisation:

    • The fusion of an egg and a sperm nucleus forms a Zygote.

    • The Zygote contains 46 Chromosomes in 23 pairs.

  • Embryo:

    • Develops from the Zygote and also contains 46 Chromosomes in 23 pairs.

LEARNING OUTCOMES

Core Ideas

  • The union of the nuclei of an egg and a sperm (inputs of a system) results in a fertilised egg that develops into a new individual (output of a system).

  • The sexual reproductive system is critical for facilitating heredity, which is the passing down of genetic material from one generation to the next.

  • New individuals formed through sexual reproduction inherit a unique combination of genetic information from both parents, leading to similarities and differences among individuals and siblings.

  • Physical changes during puberty and early adolescence occur due to hormone effects on other systems.

Practices

  1. Recognize physical changes due to Hormones:

    • Changes include height and weight increase, and secondary sexual characteristics.

  2. Evaluate Consequences:

    • Discuss the ethical and societal implications of abortion and pre-marital sex.

  3. Raise Awareness:

    • Discuss the negative impacts of drug abuse on fetuses including risks associated with smoking, alcohol, and other substance abuse.

  4. Understand Population Growth:

    • Identify reasons for the growing human population, such as advances in medicine and improved sanitation.

  5. Understand the Menstrual Cycle:

    • Describe the phases of the menstrual cycle and the reproductive system's role in this process.

  6. Explore Birth Control:

    • Describe temporary and permanent birth control methods and their mechanisms for preventing conception.

  7. STI Knowledge:

    • Recognize the harmful consequences of STIs and understand treatment options for bacterial STIs versus viral STIs.

Values, Ethics, Attitudes

  • Evaluate the consequences and ethical implications surrounding abortion and pre-marital sexual relations.

  • Understand the impact of drug abuse during pregnancy on fetal development.

FUNCTION OF THE HUMAN REPRODUCTIVE SYSTEM

Introduction to Sexual Reproduction

  • Sexual reproduction is prevalent in many organisms. It involves the formation of young when the nuclei of two sex cells (sperm and egg) fuse together, a process known as fertilization. Following fertilization, the egg develops into an embryo, eventually becoming a new individual. The offspring inherits genetic material from both parents.

HEREDITY

Definition of Heredity

  • The process of passing down genetic material from one generation to the next during sexual reproduction is termed heredity. This forms the basis of why children often resemble their parents.

  • Traits or characteristics are inherited from parents to children.

Uniqueness of Offspring

  • Despite the genetic connection, children do not appear identical to their parents; each child is a unique individual. The mixing of traits is a random process, resulting in numerous unique combinations.

  • Given that humans possess 23 pairs of chromosomes, the potential combinations of these genes are vast.

Importance of Chromosomes

  • Chromosomes exist in pairs to ensure genetic diversity during reproduction. This pairing provides the framework for mixing traits through various combinations.

PUBERTY

Overview of Puberty

  • Puberty marks a period of physical maturation, typically occurring around 11-14 years of age. It commences when specific hormones are produced.

  • Fun Fact: Hormonal changes during puberty can lead to conditions such as acne, caused by the overproduction of oil from glands.

Changes Experienced During Puberty

Males

  • Increase in height and weight.

  • Hair growth in facial, armpit, and pubic areas.

  • Deepening of voice and increase in muscle strength.

  • Production of sperm begins.

Females

  • Increase in height and weight.

  • Hair growth in armpit and pubic areas.

  • Hips become broader, breasts develop.

  • Maturation of eggs begins.

MALE REPRODUCTIVE ORGANS

Anatomy and Function

  • Sex Glands: Produce nutrient fluid to nourish sperm; combine with sperm to form semen.

  • Sperm Duct: Transports sperm from the testes to the urethra.

  • Urethra:

    • Dual function: Allows sperm to exit during ejaculation and urine to be expelled (not concurrently).

  • Penis: Deposits semen into the vagina during ejaculation.

  • Testis: Responsible for sperm production and the generation of male sex hormones that control sexual maturation.

FEMALE REPRODUCTIVE ORGANS

Anatomy and Function

  • Oviduct: Site of fertilization; egg travels through after being released from the ovary.

  • Ovary: Produces eggs and female sex hormones that influence sexual development.

  • Cervix: Serves as the opening of the uterus, connecting it to the vagina.

  • Uterus: A muscular organ where an embryo develops into a fetus; the uterine lining thickens in preparation for implantation and breaks down when fertilization does not occur.

  • Vagina: The canal where sperm is deposited, also known as the birth canal.

FERTILISATION

Process of Fertilisation

  1. The penis deposits semen containing sperm cells into the vagina.

  2. Sperm cells swim through the cervix into the uterus and then enter the oviduct.

  3. The sperm cell meets the egg cell in the oviduct.

  4. Fertilisation occurs when the nucleus of the sperm cell fuses with the nucleus of the egg cell. Other sperm cells are eliminated and broken down by the female's body.

Following Fertilisation

  • The embryo travels toward the uterus and implants into the wall of the uterus to develop into a fetus.

  • Question: What potential problems could prevent a successful pregnancy?

MENSTRUATION

Overview of the Menstrual Cycle

  • After puberty, ovaries release an egg cell approximately every 28 days. This cycle can vary based on several factors like stress, illness, and diet.

  • The menstrual cycle continues until approximately 50 years old, at which point ovaries cease releasing eggs (menopause).

Phases of the Menstrual Cycle

Days 1-5

  • The uterus sheds its inner lining, resulting in menstrual fluid.

Days 6-9

  • The lining in the uterus thickens, filled with blood vessels to prepare for possible implantation if fertilization occurs.

Days 10-15

  • An egg is released by the ovary into the oviduct on day 14 – a process called ovulation.

Days 10-15 (Fertile Period)

  • This period is when a woman is most fertile, making the likelihood of pregnancy highest when sexual intercourse occurs.

  • Survival of Sperm and Egg:

    • Sperm can survive in the female reproductive tract for 3-5 days.

    • The egg is viable for 1 day post-release from the ovary.

Days 16-28

  • The uterine lining continues to thicken. If no fertilization occurs, menstruation will commence again after day 28.

DISRUPTION OF THE HUMAN REPRODUCTIVE SYSTEM

Effects of Substance Abuse

  • Common substances affecting reproductive health include:

    • Alcohol

    • Smoking

    • Abuse of Controlled Drugs such as Cannabis and Heroin

Impact on Fetus from Substance Abuse

  • Premature Birth: Babies may not have fully developed organs and may require intensive medical care.

  • Low Birth Weight: Can lead to poorer health outcomes.

  • Underdeveloped Immune Systems: Increases susceptibility to infections.

Specific Effects of Substances

  • Smoking: May impair the development of the fetus’s heart, lungs, and brain, leading to respiratory issues and potential future health problems like obesity and diabetes.

  • Alcohol and Drug Abuse: Can result in physical, intellectual, and behavioral challenges, leading to lasting impacts on the child.

BIRTH CONTROL METHODS

Temporary Birth Control Methods

  1. Rhythm Method:

    • 76% effective. Involves tracking menstrual cycles and abstaining from intercourse during the fertile period.

  2. Condom:

    • 82% effective. A rubber covering worn on the penis to prevent sperm from entering the vagina.

  3. Spermicide:

    • A cream that kills sperm in the vagina, typically used in combination with other methods.

  4. Diaphragm:

    • 71-88% effective. A dome-shaped device placed in the vagina to cover the cervix, blocking sperm from entering the uterus.

  5. Intra-uterine Device (IUD):

    • Greater than 99% effective. A copper device inserted into the uterus, preventing fertilization and implantation; can last 3-10 years.

  6. Birth Control Pills:

    • 91% effective. Contain hormones that inhibit the release of eggs from the ovaries, preventing fertilization.

Permanent Birth Control Methods

  1. Tubal Ligation (Female):

    • Greater than 99% effective. Surgical procedure where the oviducts are cut and tied, preventing eggs and sperm from meeting.

  2. Vasectomy (Male):

    • Greater than 99% effective. Involves cutting and tying the sperm ducts to stop sperm release; sperm is still produced but is broken down.

ABORTION

Overview of Abortion

  • Definition: The termination of pregnancy involves the removal of the fetus through medical or surgical means.

  • Legal Considerations: In Singapore, abortion beyond 6 months of pregnancy is illegal unless the mother's life is at risk.

  • Reasons for Abortion:

    • Existing children in the family.

    • Accidental pregnancies.

    • Pregnancies from sexual assault.

    • Serious disabilities or genetic conditions of the fetus.

    • Maternal health concerns.

Side Effects of Abortion

  • Risks include injuries to the uterus or the potential for developing infections.

MEDICAL ASPECT OF HUMAN REPRODUCTION AND SURVIVAL

Sexually Transmitted Infections (STIs)

Transmission Methods

  • Intercourse, blood transfusion, sharing contaminated needles (e.g., injections, body piercings, tattooing), and transmission from mother to baby during childbirth or breastfeeding.

  • The primary method of transmission involves exposure to body fluids from an infected individual.

STIs Overview

  1. Syphilis (Bacterial Infection)

    • Symptoms: Painless sores, red rashes, fever, headache, muscle ache, fatigue.

    • Long-term effects if untreated: Blindness, paralysis, brain, and heart damage, potential for infertility.

  2. Gonorrhoea (Bacterial Infection)

    • Symptoms: Burning sensation during urination, pus discharge, lower abdominal pain.

    • Long-term effects if untreated: Infertility, chronic pelvic pain.

  3. HIV (Human Immunodeficiency Virus) (Viral Infection)

    • Symptoms: Early infection may show flu-like symptoms; can remain asymptomatic initially.

    • Long-term effects if untreated: Progression to AIDS, severely weakened immune system, increased susceptibility to other diseases, death.

EXTENSION: TECHNOLOGICAL ADVANCEMENTS

In-Vitro Fertilisation (IVF)

Overview of IVF

  • IVF is a process where fertilization happens in a laboratory setting.

  • Reasons for IVF: Issues with the parents' reproductive systems could hinder natural fertilization or pregnancy support.

IVF Process

  1. Extraction of sperm and egg from the parents.

  2. Mixing of sperm and egg to allow fertilisation.

  3. Monitoring of embryo development.

  4. Implantation of the embryo into the mother, with pregnancy outcomes variable.