Reproduction Flashcards
Know the roles of FSH in the processes of spermatogenesis and oogenesis.
FSH and LH are secreted by the anterior pituitary gland.
Oogenesis: FSH stimulates ONE primary oocyte (“follicle”) to mature and complete meiosis I, producing two haploid (n = 23) cells - one secondary oocyte and one polar body.
Spermatogenesis: FSH stimulates meiosis in primary spermatocytes, producing haploid (n = 23) secondary spermatocytes.
Know the roles LH in the processes of spermatogenesis and oogenesis.
FSH and LH are secreted by the anterior pituitary gland.
Oogenesis: LH is released in a “surge” to stimulate the ovulation of an “egg” from the ovary into the fallopian tube. LH stimulates the ruptured follicle inside the ovary to develop into the corpus luteum
Spermatogenesis: LH stimulates Leydig cells in the testes to produce testosterone.
Know the role of testosterone in the process of spermatogenesis and in the development of male sex characteristics.
Testosterone stimulates meiosis II in the secondary spermatocytes, producing 4 haploid (n = 23) spermatids and stimulates Sertoli cells.
Testosterone also aids in the development of male secondary sex characteristics during puberty, such as body hair, deepening voice, muscle development, etc.
Know the roles of estrogen and progesterone in the menstrual cycle/ oogenesis
During oogenesis, estrogen stimulates LH secretion so only one follicle matures at a time (follicular phase), inhibits LH and FSH release from pituitary (to prevent maturation of follicles during the luteal phase), and thickens uterine lining by stimulating it to “repair”/grow and develop new tissues rich in blood cells.
During oogenesis, progesterone thickens and maintains uterine lining (endometrium), and inhibits LH and FSH release from pituitary
Know the roles of estrogen and progesterone in the development of female sex characteristics.
Estrogen and progesterone cause prenatal development of female reproductive organs, they aid in the development of female sex characteristics such as breast development, body hair, fat deposition, etc.
Know the roles of estrogen and progesterone during pregnancy, and during parturition (birth).
During pregnancy, estrogen and progesterone maintain the highly vascular endometrium and prevent release of FSH and LH from the anterior pituitary. Estrogen also stimulates growth of uterine muscles and mammary glands’ development. Progesterone prevents uterine contractions by inhibiting oxytocin and causes development of breast tissue.
During parturition (childbirth), estrogen increases sensitivity of uterine muscles to oxytocin and inhibits progesterone. Progesterone levels drop, no longer inhibiting oxytocin and allowing uterine muscles to contract.
Outline the genetic and hormonal control of the development of male sexual characteristics (prenatal).
Males have XY sex chromosomes (23rd pair). The Y chromosomes carries a gene called SRY (Sex Determining Region Y) which codes for a protein called TDF (testis-determining factor). TDF causes embryonic gonads to develop into testes (which produce testosterone). Testosterone causes prenatal development of male genitalia and aids in sperm production (meiosis II).
Outline the genetic and hormonal control of the development of female sexual characteristics (prenatal).
Female have XX sex chromosomes (23rd pair). Since they have no Y chromosome, they don’t have the SRY gene, which means they don’t have the TDF protein. This causes the embryonic gonads to develop into ovaries (which produce estrogen and progesterone). Estrogen and progesterone cause prenatal development of female reproductive organs.
Know the roles of oxytocin, estriol (a type of estrogen), and prostaglandins in the positive feedback mechanisms of birth.
Estriol is a type of estrogen that increases uterine muscles’ sensitivity to oxytocin and inhibits progesterone. Oxytocin is released from the pituitary gland and targets uterine cells, causing muscles in the uterus to contract. The fetus becomes increasingly cramped by contractions and releases prostaglandins, which stimulate more uterine contractions. More uterine contractions trigger more oxytocin release.
Be able to explain the process of fertilization, including the mechanisms that prevent polyspermy.
Millions of sperm enter the oviduct (fallopian tube). The sperm then swim towards the egg (secondary oocyte). Acrosome vesicles on sperm cells that penetrate the follicle cells bind to receptors on the zona pellucida of the egg and release hydrolytic enzymes from their acrosome to digest through it (acrosome reaction). Once a sperm penetrates the zona pellucida, it binds to “docking proteins” on the egg membrane. Following this, the membranes of sperm and egg fuse and the sperm nucleus (and centrioles) enter the egg. Calcium ions are released into the egg, triggering the final meiotic division in the egg nucleus. Calcium ions also stimulate the cortical reaction - vesicles are stored in the egg cytoplasm just inside the plasma membrane, fuse with the plasma membrane, and release enzymes that destroy sperm-binding proteins on the “egg” plasma membrane, hardening it. This prevents polyspermy.
Know the function and the origin of the hormone hCG.
hCG stimulates the corpus luteum (in the ovary) to secrete estrogen and progesterone during early pregnancy (to thicken the cervix, maintain the highly vascularized endometrium, and to inhibit FSH and LH release).
Between 7-9 days (post-fertilization) the embryo “hatches” out of the zona and implants itself (using enzymes and hormones) into the endometrium of the uterus and begins to secrete hCG.
Be able to outline the structure and function of the placenta.
The placenta nourishes the embryo/fetus and secrete hormones to maintain the pregnancy after the corpus luteum degrades.
Fetal blood vessels (umbilical cord) branch into capillaries that are contained in structures in the placenta called microvilli (placental villi, chorionic villi, etc) - these increase surface area for exchange of molecular materials.
Microvilli are surrounded by intervillous spaces (lacunae), where maternal blood pools.
The chorion (chorionic plate) is a thin, cytoplasm-filled barrier between maternal blood and fetal blood - allowing for the exchange of molecular materials without maternal and fetal blood mixing.
Be able to explain the process of IVF.
- Drugs are used to down-regulate the menstrual cycle, preventing the natural release of FSH and LH from the pituitary gland.
- High doses of FSH are injected to stimulate many follicles to develop. Eventually, hCG is injected to cause those many follicles to mature.
- Eggs are harvested through follicular aspiration (involves outpatient operation and a VERY LONG needle), with the help of an ultrasound to observe the eggs.
- Male produces sperm, which is washed and processed.
- Eggs are fertilized through either:
- In vitro fertilization: Sperm is mixed with eggs in a petri dish and fertilizes them “naturally.”
- ICSI (IntraCytoplasmic Sperm Injection): One sperm is directly injected into each egg with microscopic equipment when low numbers of motility is a factor.
- Fertilized eggs are kept in petri dishes for 3-5 days in an incubator at 37 degrees Celsius, where they grow and develop.
- 1-3 of the best embryos are transferred back into the women’s uterus. Prior to this, a woman takes progesterone for about 2 weeks
- 14 days to one month after embryo transfer a pregnancy test is administered to determine if embryo implantation in the uterine wall has occurred.
