GAMETOGÉNESIS (Ovogénesis y Espermatogénesis paso a paso)

How Are Oocytes and Spermatozoa Formed?

Introduction

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Spermatogenesis

• The process of spermatogenesis is introduced as the formation of spermatozoa from spermatogonia, occurring in the seminiferous tubules of the testes.

• After formation, spermatozoa move to the epididymis for maturation; this entire process takes approximately 65 to 72 days.

• Spermatogonia undergo mitosis to produce two types of cells: type A (which remain as spermatogonia) and type B (which develop into sperm).

• Type B cells undergo meiosis, resulting in four haploid spermatids from each primary spermatocyte.

• The transformation from spermatid to mature spermatozoon is termed spermiogenesis.

Oogenesis

• Oogenesis begins with an oogonium that develops into an ovum within the ovaries; it also involves mitotic divisions producing diploid cells.

• Unlike spermatogenesis, oogenesis results in one viable gamete (the ovum), while three polar bodies are produced during meiosis.

• This lengthy process starts early in gestation when around 7 million oogonia are formed but reduces significantly due to degeneration.

• By puberty, only about 40,000 oogonia remain, with roughly 400–500 maturing throughout a woman's reproductive life.

Follicular Development

• During gestation's third to eighth month, primary oocytes begin their first meiotic division but pause at prophase until puberty.

• At puberty, hormones stimulate growth of primordial follicles; follicular cells transition from flat to cuboidal shapes surrounding the oocyte.

• As development continues, multiple layers form around the oocyte creating secondary follicles filled with follicular fluid known as antral follicles.

• By day 14 of this cycle, a mature follicle (Graafian follicle) forms as primary oocytes complete their first meiotic division and initiate second meiosis.

Understanding the Role of the Corpus Luteum in Reproductive Biology

The Function of the Corpus Luteum

• When fertilization occurs, the remnants of the follicle transform into a structure known as the corpus luteum.

• The primary function of the corpus luteum is to secrete hormones, specifically progesterone and estrogens.

• These hormones are crucial for maintaining an active endometrium for approximately 14 days, providing a suitable environment for potential implantation of a fertilized egg (zygote).

• If fertilization does not occur, the corpus luteum eventually degenerates into a structure called the corpus albicans.