Secondary oocyte

Definition

A secondary oocyte is an immature female gamete that is formed during the process of oogenesis, specifically after the completion of the first meiotic division. This stage occurs just prior to ovulation, and the secondary oocyte is characterized by having half the original chromosome number, making it haploid, and it retains most of the cytoplasm from the original primary oocyte. If fertilization occurs, the secondary oocyte will complete the second meiotic division to form a mature ovum.

5 Must Know Facts For Your Next Test

1. The secondary oocyte is produced from a primary oocyte during oogenesis and is haploid with 23 chromosomes in humans.
2. At ovulation, the secondary oocyte is released into the fallopian tube where it can potentially be fertilized by sperm.
3. If fertilization does not occur, the secondary oocyte will degenerate and not complete the second meiotic division.
4. The secondary oocyte's cytoplasmic division during meiosis is uneven, resulting in one larger cell (the ovum) and a smaller polar body that typically disintegrates.
5. Hormonal signals from the pituitary gland, particularly luteinizing hormone (LH), trigger the final maturation and release of the secondary oocyte.

Review Questions

• How does the formation of a secondary oocyte relate to the overall process of oogenesis?
  • The formation of a secondary oocyte is a key step in oogenesis, which involves several stages of maturation. Initially, a primary oocyte undergoes meiosis but is arrested in prophase I until puberty. During each menstrual cycle, one primary oocyte completes the first meiotic division, producing a secondary oocyte and a polar body. This transition marks an important point where the cell prepares for potential fertilization while retaining most of its cytoplasmic resources.
• Discuss the significance of ovulation in relation to secondary oocytes and fertility.
  • Ovulation is crucial for fertility as it involves the release of a secondary oocyte from the ovary. This event allows for the possibility of fertilization if sperm are present in the fallopian tube. The timing of ovulation in relation to a woman's menstrual cycle determines her fertile window, emphasizing how essential the secondary oocyte is for reproduction. A well-timed ovulation can significantly increase chances of conception.
• Evaluate how hormonal regulation impacts the maturation and release of secondary oocytes during the ovarian cycle.
  • Hormonal regulation plays a vital role in controlling both the maturation and release of secondary oocytes throughout the ovarian cycle. Luteinizing hormone (LH) surges trigger ovulation by inducing the final maturation of the follicle containing the secondary oocyte. Additionally, follicle-stimulating hormone (FSH) helps stimulate follicular development leading up to ovulation. Disruptions in these hormonal signals can affect regular ovulation patterns and influence overall fertility.

Related terms

oogenesis: The process by which female gametes, or ova, are produced in the ovaries through a series of developmental stages.

primary oocyte: An immature female gamete that undergoes meiosis to produce secondary oocytes; it is formed during fetal development and is arrested in prophase I until puberty.

ovulation: The release of a secondary oocyte from the ovary, marking a crucial step in the menstrual cycle and reproductive process.