Oogenesis_edt_Phoenix

GAMETOGENESIS Formation and development of specialized generative cells (gametes). Prepares sex cells for fertilization. Chromosome number is reduced by half during meiosis. Cells' shapes are altered; before DNA replication: single-chromatid, after: double-chromatid. Male gamete maturation: spermatogenesis, female gamete maturation: oogenesis.

NORMAL GAMETOGENESIS SPERMATOGENESIS Development of spermatozoon (haploid, 23n) in testes. Begins from primary spermatocyte to secondary spermatocyte and eventually to spermatids.

OOGENESIS Development of oocyte (haploid, 23n) in ovaries. It begins with the formation of primordial germ cells, which then differentiate into primary oocytes during fetal development. Each primary oocyte is arrested in prophase I of meiosis until puberty, when a selected group resumes maturation monthly. The primary oocyte undergoes meiosis I to produce a secondary oocyte and a polar body, which is typically nonviable. The secondary oocyte is then arrested in metaphase II and will only complete meiosis if fertilization occurs. If fertilization takes place, the secondary oocyte will divide into a mature ovum and another polar body, producing a total of one viable gamete.

STAGES OF GAMETOGENESIS Primordial germ cells proliferate via mitosis. Transition to differentiation via meiosis, resulting in primary and secondary gametes.

HORMONAL CONTROL Hypothalamus releases Gonadotropin-releasing hormone (GnRH). Anterior pituitary secretes LH and FSH controlling ovarian activities.

MENSTRUAL CYCLE Cycle phases: Menstrual phase, Proliferative phase, Luteal phase. Regular cycles occur from puberty until menopause (approx. 28 days).

OVULATION Secondary oocyte release under influence of LH; involves the rupture of the follicle and formation of the corpus luteum.

SPERM TRANSPORT & FERTILIZATION Sperm travels from vagina through cervix to fertilization site in the ampulla. Capacitation precedes fertilization; acrosome reaction enables sperm to penetrate zona pellucida of the oocyte.

COMPARISON OF GAMETES Oocyte: larger, immotile; Sperm: smaller, highly motile. Both are haploid cells but differ in origin, structure, and hormone regulation.

ASSISTED FERTILITY Techniques include IVF, GIFT, and ZIFT for women with fertility issues. Involves collection and fertilization of eggs outside the body followed by their insertion into uterus.