Chapter 17 Reproductive System: Gametogenesis, Hormones, and Fertility

What is gametogenesis?

The production of sex cells, sperm or ova, containing 23 chromosomes.

What are the two main processes involved in gametogenesis?

Mitosis and meiosis.

What occurs during mitosis in gametogenesis?

The 46 chromosomes of the dividing cell are replicated, producing daughter cells with a full set of 46 chromosomes.

What is the result of meiosis in gametogenesis?

Each resulting gamete receives only 23 chromosomes from each homologous pair.

What determines the sex of an individual?

The genetic inheritance of sex chromosomes (X and Y).

What chromosomes do males and females possess?

Males have one X and one Y chromosome; females have two X chromosomes.

What gene is responsible for male gonadal differentiation?

The SRY gene located on the Y chromosome.

When does gonadal differentiation begin in males?

During the seventh week of fetal development.

What happens in the absence of the SRY gene?

Ovaries begin developing in the 11th week of fetal development.

What is Androgen Insensitivity Syndrome?

A condition where an XY genotype has testes secreting androgen, but the androgen receptors do not respond, resulting in a female phenotype.

What is congenital adrenal hyperplasia?

A condition in XX individuals where a gene mutation leads to excess androgen production, resulting in a male or ambiguous phenotype.

What hormonal changes occur from fetal life to adulthood?

GnRH and gonadotropins are high during fetal life, low during childhood, and increase during puberty.

What is the role of Sertoli cells in the testis?

They nourish developing sperm, secrete inhibin, and secrete anti-müllerian hormone during fetal development.

What are the effects of testosterone in males?

Decreases GnRH secretion, maintains spermatogenesis, induces male secondary sex characteristics, and stimulates erythropoietin secretion.

How does testosterone affect the brain?

It is converted into estradiol by aromatase, which is active in parts of the brain related to sexual and reproductive activities.

What is the process of ejaculation?

It involves emission of sperm and glandular secretions into the urethra followed by expulsion through rapid contractions.

What happens during the emission phase of ejaculation?

Smooth muscles contract to empty sperm and glandular secretions into the urethra.

What is the average volume of semen expelled during ejaculation?

Approximately 3 milliliters containing around 300 million sperm.

What is the impact of anabolic steroid abuse in male athletes?

It can increase muscle mass but leads to decreased endogenous testosterone, reducing testicular size and sperm count.

What is Klinefelter's Syndrome?

A condition caused by nondisjunction of chromosomes during meiosis, resulting in an XXY genotype with testicular development but low testosterone.

What are the characteristics of Klinefelter's Syndrome?

Small penis, female pubic hair distribution, gynecomastia, and abnormal development of the vas deferens and testes.

What is the role of inhibin in the male reproductive system?

It inhibits FSH secretion from the pituitary gland.

What is spermatogenesis?

The process of sperm cell development that begins at puberty.

What is the significance of the hypothalamic release of GnRH?

It initiates puberty and the maturation of reproductive organs in both males and females.

What is the function of Leydig cells?

They produce testosterone in response to stimulation.

What is the difference between menopause and andropause?

Menopause is the cessation of reproductive function in women, while andropause refers to the gradual decline in male reproductive function.

What is the embryonic structure from which testes and ovaries develop?

The urogenital ridge.

What is the primary hormonal change during puberty in males?

An increase in GnRH, gonadotropins, and gonadal sex hormones.

What gene is responsible for testicular development?

The SRY gene

What are the consequences of low testosterone levels in males?

Small penis, female pubic hair distribution, gynecomastia, abnormal development of the vas deferens and testes.

What is hypogonadism?

A condition characterized by low testosterone levels leading to various developmental issues.

What is androgen replacement therapy?

A treatment for hypogonadism involving the administration of testosterone.

What is andropause?

A gradual decrease in testosterone secretion in men, typically starting around age 40.

What emotional problems may increase in men during andropause?

Depression and emotional instability.

What is oogenesis?

The production of gametes during the fetal period.

What is ovulation?

The expulsion of the mature oocyte from the ovary.

What hormones are secreted by the ovaries?

Estrogen, progesterone, and inhibin.

What happens during the proliferative phase of the menstrual cycle?

The endometrium thickens in preparation for potential implantation.

What triggers the LH surge that causes ovulation?

A high level of estrogen through positive feedback.

What are some effects of estrogen on the female reproductive system?

Stimulates growth of ovaries and follicles, increases uterine contractions, and prepares the endometrium for progesterone.

What is the role of progesterone in the menstrual cycle?

Converts the estrogen-primed endometrium to a secreting tissue suitable for embryo implantation.

What is menarche?

The first menstruation, typically occurring around 12.5 years of age in the U.S.

What is perimenopause?

The phase of life during which menstrual irregularity begins.

What causes menopause?

Ovarian failure leading to the cessation of menstrual cycles.

What is capacitation in sperm?

The process that enables sperm to fertilize an egg, involving changes in motility and membrane properties.

Where does fertilization typically occur?

In the fallopian tube.

What is the success rate of in vitro fertilization when one egg is transferred?

May be as high as 40% depending on the cause of infertility.

What percentage of reproductive-age individuals in the U.S. are infertile?

Approximately 6% to 15%.

What is the effect of estrogen on bone growth?

Estrogen protects against osteoporosis and regulates the closure of epiphyseal plates.

What are the effects of progesterone on the uterus?

Decreases contractions and prepares the endometrium for implantation.

What hormonal changes occur during menopause?

Increased secretion of gonadotropins due to decreased estrogen and inhibin.

What is the role of inhibin in the female reproductive system?

Inhibits the secretion of gonadotropins from the pituitary gland.

What is the primary cause of infertility in women?

Various factors including hormonal imbalances, structural issues, or age-related factors.

What are some effects of female sex steroids on the reproductive tract?

Stimulate growth and contractions in the fallopian tubes and uterus.

What is the relationship between estrogen and cholesterol?

Estrogen protects against atherosclerosis by affecting plasma cholesterol levels.

What is the significance of the fimbriae during ovulation?

They help sweep the released egg into the fallopian tube.