Explain the hormonal regulation of the menstrual cycle, including the roles of FSH, LH, estradiol, and progesterone.
FSH (follicle-stimulating hormone) stimulates follicle maturation in the ovary, leading to estradiol (an estrogen) secretion by the follicle. Rising estradiol levels trigger a surge in LH (luteinizing hormone), which causes ovulation (release of the ovum). After ovulation, the ruptured follicle becomes the corpus luteum, which secretes progesterone (and some estradiol) to maintain the uterine lining and inhibit further FSH and LH release. If pregnancy does not occur, the corpus luteum degenerates, progesterone and estradiol levels fall, and the menstrual cycle restarts.
What is the main difference between sexual and asexual reproduction in animals?
Sexual reproduction involves the fusion of male and female gametes to form a diploid zygote, while asexual reproduction produces offspring from a single parent without gamete fusion.
Where does spermatogenesis occur and what is the role of the epididymis?
Spermatogenesis occurs in the seminiferous tubules of the testes, and the epididymis is where sperm mature and are stored before ejaculation.
Describe the path sperm take from production to ejaculation in the male reproductive system.
Sperm are produced in the seminiferous tubules, mature in the epididymis, travel through the vas deferens, mix with fluids from accessory glands, and are expelled through the urethra during ejaculation.
What is the function of the corpus luteum in the female reproductive cycle?
The corpus luteum secretes progesterone (and some estradiol) to maintain the uterine lining and inhibit further release of FSH and LH after ovulation.
How does oogenesis differ from spermatogenesis in terms of timing and cell output?
Oogenesis begins before birth, pauses until puberty, and produces one mature ovum and polar bodies per cycle, while spermatogenesis starts at puberty and produces four sperm from each spermatogonium.
What triggers ovulation during the menstrual cycle?
A surge in luteinizing hormone (LH), triggered by rising estradiol levels from the maturing follicle, causes ovulation.
Explain the process and significance of the cortical reaction during fertilization.
The cortical reaction occurs when the sperm fuses with the egg membrane, releasing enzymes that alter the egg's membrane to prevent polyspermy, ensuring only one sperm fertilizes the egg.
What is the role of the placenta during pregnancy?
The placenta facilitates the exchange of nutrients, gases, and wastes between the mother and fetus and is formed from the trophoblast cells of the blastocyst.
Which hormones regulate the menstrual cycle and what are their primary roles?
FSH stimulates follicle maturation, estradiol triggers the LH surge for ovulation, LH causes ovulation and corpus luteum formation, and progesterone maintains the uterine lining and inhibits FSH and LH.