Biology with Zhan Xuan: Reproduction in Humans

Introduction

• Topic: Reproduction in Humans (Chapter 15)
• Syllabus Range: 15.5 to 15.11
• Disclaimer: Viewer maturity required; for educational purposes only.

Section 1: Sexual Reproduction

• Types of Reproduction: Asexual and Sexual
• Definition: Fusion of nuclei of two gametes (sex cells) to form a zygote, producing genetically different offspring.
• Key Terms:
  • Zygote: Fertilized egg cell
  • Fertilization: Fusion of gamete nuclei
  • Haploid: Gamete nuclei, containing half (23) of the chromosomes
  • Diploid: Zygote nuclei, containing full (46) set of chromosomes
• Process: Sperm + Ovum (haploid) -> Diploid Zygote
• **Advantages of Sexual Reproduction: **
  • Genetic variation
  • Reduced risk of extinction
  • Variety in crop yield
• Disadvantages:
  • Time-consuming
  • Resource-intensive
  • Requires a mate
  • Lower crop yield
  • Less economic gain
  • Uncontrollable offspring phenotypes

Section 2: Human Reproductive Systems

Female Reproductive System

• Parts and Functions:
  • Ovary: Produces ovum
  • Oviduct/Fallopian Tube: Site of fertilization
  • Uterus (Womb) & Lining: Site of zygote implantation
  • Cervix: Allows menstrual blood flow to vagina
  • Vagina: Receives the penis during intercourse

Male Reproductive System

• Parts and Functions:
  • Testis: Produces sperm
  • Scrotum: Maintains testis temperature
  • Prostate Gland: Secretes alkaline fluid to protect sperm
  • Urethra: Carries semen and fluid during erection
  • Penis: Transfers sperm to cervix
  • Epidermis: Stores sperm
  • Sperm Duct: Transports semen from testis to urethra

Gamete Differences

• Sperm (Male Gamete): Small, elongated, streamline, mobile (flagellum), produced in millions
• Ovum (Female Gamete): Large, spherical, rich in protein and fat, non-motile, produced once per month

Section 3: Fertilization and Implantation

• Process:
  1. Sperm and ovum meet during sexual intercourse
  2. One sperm penetrates ovum, forming a zygote (fertilized egg)
  3. Zygote undergoes mitosis, forming an embryo
  4. Embryo implants into uterus lining, beginning pregnancy
• Importance of Amniotic Fluid: Protects embryo
• Function of Placenta and Umbilical Cord:
  • Placenta provides oxygen/nutrients, removes waste
  • Umbilical cord connects embryo to placenta
• Implantation: Attachment of fertilized egg to uterine lining

Section 4: Puberty and Menstrual Cycle

• Puberty: Changes in physical characteristics and hormone production
• Menstrual Cycle: Approximately 28 days
  • Follicular Phase: Development of follicles, ovulation
  • Luteal Phase: Preparation for potential pregnancy
  • Hormones Involved:
    • FSH (Follicle Stimulating Hormone)
    • Estrogen
    • LH (Luteinizing Hormone)
    • Progesterone

Section 5: Birth Control Methods

• Types:
  1. Chemical: IUD, IUS, contraceptive pills, implants, injections
  2. Mechanical: Condoms, femidom, diaphragm
  3. Surgical: Vasectomy (male), oviduct cutting (female)
• Removal from 2023 Syllabus: Not required but useful to know

Section 6: STIs (Sexually Transmitted Infections)

• Definition: Infections transmitted via body fluids through sexual contact
• Examples: HIV/AIDS
  • HIV: Infects and destroys lymphocytes, weakening immune system
  • Transmission Methods: Needle sharing, unprotected sex, mother-to-fetus, blood transfusion
  • Prevention: Avoid unprotected sex, safe practices

Conclusion

• Final Notes: Importance of understanding reproduction, impacts of STIs, and prevention methods.

Next Steps

• Preparation: Time to digest and understand information
• Upcoming Topics: Continuation of biology syllabus