ASEXUAL REPRODUCTION

Gametogenesis

• Processes: Oogenesis (egg formation) and Spermatogenesis (sperm formation)

• Both involve nuclear division and meiosis.

• Cytokinesis differs:

  • Spermatogenesis: Even division resulting in 4 sperm.

  • Oogenesis: Uneven division leading to 1 egg and 3 polar bodies.

• Spermatogonium: Diploid cells (2n) replicate to form 2nR.

Meiosis

• Each meiosis divides twice:

  • First division: nR and nR.

  • Second division: results in four n (haploid) cells.

Oogenesis

• Takes place in ovaries.

• Primary oocyte is diploid (2n) and undergoes replication.

• Maturation leads to one egg being fully formed.

Fertilization Process

• Sperm swims through fallopian tubes to fertilize the egg, forming a zygote.

• Progression: Zygote undergoes mitosis to initiate embryonic development.

Gastrulation

• Cells migrate, forming a gastrula, with subsequent differentiation.

• Stem cells: Initially undifferentiated, later specialized based on position.

Layers of Gastrula

• Ectoderm (outer layer): Develops into skin and nerves.

• Mesoderm (middle layer): Forms muscles and various organs.

• Endoderm (inner layer): Creates the digestive tract.

Neural Development

• Primitive digestive cavity: Archenteron.

• Neural tube forms from ectoderm, developing into spinal cord and brain.

• Neural tube defects may lead to issues such as spina bifida.