Meiosis and Embryology of Reproductive System

Meiosis and Germ Cell Formation

• Females produce one ovum (23X) after meiosis, while males generate four spermatozoa (2 with 23X and 2 with 23Y).
• Female development is neuter; the presence of the Y chromosome is crucial for male development.
• In females, one X chromosome is active in somatic cells; the inactive X condenses into a Barr body.
• Human chromosomes can be analyzed by culturing cells, arresting mitosis with colchicine, staining, and microscopy.

Embryology of the Reproductive System

• Gonads are identical until the 6th week of intrauterine life, derived from the genital ridge on the posterior abdominal wall.
• Germ cells migrate to the genital ridge by the 3rd week; 46XX chromosomes lead to ovary development, while 46XY results in testes.
• Genital differentiation begins at 8 weeks, with distinguishable male and female structures identifiable by 10-12 weeks.
• In absence of functional testes, Müllerian ducts develop into female reproductive structures; presence of testes leads to regression of these ducts.

Menstrual Cycle and Menopause

• Menopause is the complete cessation of menstruation diagnosed after one year without a period, occurring between ages 45-55.
• Female gonadal aging results in ovarian follicle atrophy and reduced estrogen levels, leading to elevated gonadotropins.
• Climacteric denotes the transitional phase leading to menopause; includes psychological, vasomotor, and physical changes.
• Hormone replacement therapy may alleviate post-menopausal symptoms; premature menopause occurs before age 40.

Physiology of Human Sexual Response

• Masters and Johnson conducted foundational studies on human sexual responses, compiling data from numerous participants.
• Females experience engorgement and lubrication; the interoital opening is reduced, forming an orgasmic platform.
• Orgasm represents peak sexual tension, with coordinated muscular contractions; males experience ejaculation simultaneous with orgasm.
• Females can have multiple orgasms, characterized by rapid muscle contractions and euphoric sensations.

Spermatogenesis

• Spermatogenesis begins at puberty, producing 100-200 million sperm daily, occurring in the seminiferous tubules.
• Mitosis starts with spermatogonia that divide into primary spermatocytes.
• Meiosis occurs when primary spermatocytes divide into secondary spermatocytes, producing four haploid spermatids per primary spermatocyte.
• Spermiogenesis involves maturation of spermatids into spermatozoa within Sertoli cells.

Structure and Function of Spermatozoa

• Mature spermatozoa consist of a head (with acrosome), middle piece (energy storage), and tail (for propulsion).
• Sertoli cells support sperm maturation and secretes hormones, including Müllerian inhibiting factor and inhibin.
• Mature spermatozoa are stored in the epididymis for up to a month, gaining motility as they travel through the male reproductive tract.

Fertilization Process

• Capacitation enhances sperm ability to fertilize; uterine fluids remove inhibitory factors.
• The acrosomal reaction involves enzymatic release for penetrating the egg's protective layers during fertilization.

Composition of Semen

• Semen consists of spermatozoa (10%), seminal vesicle secretions (60%), prostate secretions (30%), and additional glandular contributions.

Explore the intricate details of meiosis and the formation of germ cells in this quiz. Learn about the differences in reproductive cell production between males and females, as well as the embryological development of the reproductive system. Test your knowledge on chromosome behavior and the formation of reproductive structures.