Reproduction and Development

• Fertilization and meiosis alternate during the entire life cycle
• Gametes serve as vehicles to deliver and combine parents’ DNA
• Diploid

  • completed chromosomes
• Zygote then develops into an embryo
• Human Life stages

  1. Infancy
  2. Childhood
  3. Adolescent
  4. Adulthood
• Various changes during puberty in humans serve as physical, physiological, and behavioral preparations for adulthood
• In human reproduction, mode is exclusively sexual, no viable asexual means
• Genetic material from two sources is combined to form a new organism.
• Testis (plural: testes)

  • male gonad that produces sperm cells
• Scrotum: a pouch of skin containing the testicles
• Epididymis: A coiled tube that transports sperm from the testes to the urethra
• Seminal vesicle: contributes alkaline fluid that nourishes and protects sperm cells
• Prostate gland: contributes a fluid that neutralizes semen and vaginal fluid
• Bulbourethral Gland: Located in the bulbourethral region of the penis.
• Female reproduction parts:

  1. Uterus
  2. Cervix
  3. Ovum
  4. Fallopian Tube
  5. Vagina
  6. Urethra
  7. External Genitalia
  8. Bartholin’s Gland
• Gametogenesis: the process of producing gametes, or sex cells, in animals
• Spermatogenesis: the process of sperm production in the testes
• Proliferation

  • spermatogonium undergoes several mitotic divisions to produce more spermatogonia
• Spermatogenesis

  1. Stars off with primordial cells (spermatogonium/spermatogonia(plural))
  2. undergoes mitosis, to create primary spermatocyte and spermatogonium
  3. splits creating secondary spermatocyte
  4. the secondary spermatocytes divides into two, creating spermatid/immature sperm cells
  5. Develops into mature sperm cells
• Oogenesis

  • occurs in ovaries and fallopian tubes
  • follicles of the ovary exert hormonal influence
  • starts during the pregnancy of the mother
• Process of Oogenesis:

  1. a germinal cell (diploid) creates one primary oocyte (diploid)
  2. primary oocyte undergoes meiosis, diving into two - creating a polar body and a secondary oocyte
  3. polar body and secondary oocyte (haploid) undergoes meiosis II creating 2 polar bodies, and polar body and ovum(haploid), respectively
• egg cells releases chemo attractants, choosing one specific sperm
• During the pre-implantation phase, the resulting zygote from fertilization undergoes repeated cell divisions
• On the third week, the offspring becomes a three-layered embryo through the process of gastrulation
• Three layered Embryo:

  1. Ectoderm (outer layer)
  2. Mesoderm (middle layer)
  3. Endoderm (inner layer)
• Ectoderm

  • forms skin, and nervous system
• Mesoderm

  • forms muscles, bones, respiratory organs, cartilage, etc.
• Endoderm

  • forms GI tract, liver, and reproductive organs
• Allantois and Yolk sac creates the umbilical cord of a baby
• Gestation

  • when the baby is born after 9 months of pregnancy
• Embryonic and Fetal development

  1. Germinal (0-2 weeks)
  2. Embryonic (3-8 weeks)
  3. Fetal (9 weeks-birth)
• Embryonic phase is the crucial part of developing the baby, as it will be very vulnerable to harmful ways
• 1. The human life cycle starts with fertilization and is accompanied by a series of growth stages. true
• 1. During fertilization, the male's sperm cell unites with the female's egg cell, which combines the genetic material from both parents. true
• 1. The process of organ formation or neurulation starts during the third week of development after fertilization. false
• 1. At the onset of the embryonic period, the embryo also starts to increase in size due to active tissue and organ development. true
• 1. The first meiotic division during oogenesis produces two secondary oocytes for every primary oocyte. false
• 1. The growth phase in spermatogenesis is more pronounced than that in oogenesis. false
• 1. Both the yolk sac and allantois give rise to the umbilical cord of the developing embryo. true
• 1. The fertilized egg will first undergo a series of cellular divisions before it gets implanted in the uterus of the mother. true