oocyte

An oocyte, also known as an egg cell or ovum, is a haploid female gamete responsible for reproduction in many organisms, including humans. It develops within the ovaries of females and plays a crucial role in fertilization and the formation of a zygote. The process of oocyte formation begins during fetal development, when germ cells differentiate into oogonia, which then undergo mitosis to produce more oogonia. By the time a female is born, these oogonia have already begun meiosis, but the process halts at the prophase stage of meiosis I until puberty.

During the menstrual cycle, one oocyte per month is selected for maturation in the ovary. This process involves a series of hormonal signals, primarily from follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which stimulate the growth of a follicle around the oocyte. The oocyte itself remains in a dormant state until ovulation, when it is released from the ovary. Following ovulation, the oocyte remains viable for approximately 12 to 24 hours, during which it can be fertilized by a sperm cell.

Upon fertilization, the oocyte completes meiosis II, producing a mature egg and a second polar body. The resulting zygote then undergoes rapid cell divisions to form an embryo. In humans, the process of oocyte development is highly regulated and sensitive to hormonal and environmental factors. Dysfunction in oocyte development or maturation can lead to infertility issues, highlighting its importance in reproductive health. Research continues to explore the mechanisms underlying oocyte biology, aiming to improve fertility treatments and understanding reproductive processes.