Chapter 2.3 Flashcards
What is the path an egg takes in the female reproductive system?
Once a month after puberty has begun, an egg will ovulate from the ovary into the peritoneal sac (lines abdominal cavity). From the abdominal cavity, the egg will move through the fallopian tube where it will be fertilized and end up in the uterus where it will implant into the endometrium.
What is oogenesis?
Oogenesis refers to the production of female gametocytes, otherwise known as ova or eggs.
In what 3 ways are oogenesis different than spermatogenesis?
- There are a finite amount of eggs in a female and the number of eggs is determined at birth. Sperm cells, on the other hand, can be produced indefinitely.
- By birth, all of the oogonia have already undergone DNA replication and thus are already primary oocytes. These primary oocytes are frozen in Prophase I.
- Oogenesis halts secondary oocytes at Metaphase II. The secondary oocyte will wait to be fertilized before completing Meiosis II.
What is a menarche?
Menarche is the term used to refer to a woman’s first menstrual cycle
What is the menstrual cycle?
The menstrual cycle is the monthly process where a primary oocyte is allowed to complete Meiosis I, become a secondary oocyte, and potentially be fertilized by a sperm.
What is a polar body?
In oogenesis, cytoplasm is split unevenly in order to create 3 non functional cells and 1 relatively massive oocyte. The small nonfunctional bodies that receive little cytoplasm are polar bodies.
What are the two layer surrounding Oocytes?
- The zona pellucida
- Corona radiata
What is the structure and function of the zona pellucida?
The zona pellucida is an acellular mixture of glycoproteins that protect the oocyte and allow sperm to bind to the oocyte.
What is the structure and function of the corona radiata?
The corona radiata is a layer of cells that adhere to the oocyte during ovulation. These cells are the first to be penetrated by the sperm and are responsible for communicating to the secondary oocyte that it is time for it to finish Meiosis II. This results in the production of a mature ovum and a polar body.
What is a zygote?
A zygote is an ovum that has been successfully fertilized by sperm, has a diploid set of chromosomes, and will replicate over time into the many cells that make up a person.
Describe the relative contribution of organelles and cytoplasm to the zygote made by a sperm and an ovum
Both the sperm and the ovum contribute half of the genetic information to the zygote, but the ovum basically supplies everything else. Remember, the ovum is a very large cell with high quantities of organelles, proteins, cytoplasm, etc. The sperm basically just contributes its piece of the DNA and that’s it.
From whom do we inherit our mitochondria and why?
We inherit our mitochondria from our mother because the Ovum is the cell with all of the cytoplasm and the organelles. The sperm just contributes its half of the DNA and then degrades.
In what way does FSH affect the testes?
FSH causes the Sertoli Cells to trigger sperm maturation.
MNEMONIC: Follicle Stimulating hormone Stimulates the Synthesis of Sperm by the Sertoli Cells
In what way does LH affect the testes?
LH causes the interstitial cells aka Leydig cells of the testes to produce testosterone.
MNEMONIC: LH -> Low Hair -> Side effect of too much testosterone.
What is GnRH?
Gonadotropin-releasing Hormone is a hypothalmic hormone. When synthesized and released, it stimulates the release of Follicle Stimulating Hormone (FSH) and Leutinizing Hormone (LH) by the anterior pituitary.
How does the presence of GnRH change as we mature?
GnRH is tightly regulated by the hypothalamus until puberty, at which point GnRH is released in pulses which lead to the development of secondary sex-characteristics.
What are primary sex characteristics?
Primary sex characteristics are the sex organs with which you were born that developed during fetal development.
What are secondary sex characteristics?
Secondary sex characteristics are the physical changes that we associate with men and women that occur as a consquence of primary sex characteristics at puberty.
Secondary sex characteristics include increased muscle mass, facial hair, and lowering of voice in men and widening of hips, development of breasts, and heightening of voice in females.
Which hormone is responsible for the secondary sex characteristics in men?
Testosterone
What two hormones do the ovaries produce?
Estrogen and progesterone
What 3 things does Estrogen do in females?
- Estrogens result in the development of secondary sex characteristics for adult females.
- In the embryo, estrogen stimulates the development of the female reproductive track.
- Finally, estrogens also lead to the initial thickening of the endometrium each month in preparation for implantation of a zygote.
What is the endometrium?
The endometrium is the inner lining of the uterus.
What are the 2 functions of the endometrium?
- In day to day life, the endometrium keeps adjacent walls of the uterus from sticking together, thereby maintainign its patency.
- During menstruation, the endometrium grows in to a thick blood vessel rich tissue that can optimally support a blastocyst in the case of implantation. If a blastocyst is not implanted, the thickened endometrium will slough off.
In what way does FSH affect the ovaries?
FSH stimulates the growth of the follicles in the ovaries.
In what 2 ways does LH affect the ovaries?
A sharp spike in LH during menstruation causes ovulation.
After ovulation, LH stimulates the corpus luteum to secrete progesterone
What is the function of progesterone?
- Progesterone contributes to the development and maintenance of the endometrium, but not its original thickening (That’s estrogen’s job!)
What are the 4 stages of menstruation?
- Follicular Phase
- Ovulation
- Luteal Phase
- Menstruation
What occurs in the Follicular Phase of Menstruation?
The follicular phase begins when the uterine lining of the previous cycle begins to shed.
- As Estrogen and Progesterone fall in response to the death of the corpus luteum, GnRH is secreted in response.
- GnRH secretion leads to the rise of FSH and LH.
- FSH and LH work together to cause the follicles in the ovary to grow (Mostly FSH though)
- As the follicles grow, they release estrogen, which negatively inhibits the hypothalamus and causes a drop in GnRH, which slows the increase of FSH and LH.
- The estrogen that has been released gets to work on re-thickening the endometrium (decidua).
What occurs in Ovulation?
- Developing follicles release Estrogen. As the follicles grow they eventually get so big they are releasing a lot of Estrogen. Estrogen is interesting because it negatively inhibits the hypothalamus at low concentrations, but after a certain concentration is surpassed, it will conduct positive feedback on the hypothalamus.
- This increase in GnRH by the hypothalamus leads to a spike in FSH and LH levels.
- The spike in LH levels induces ovulation.
What is ovulation?
Ovulation is the process by which a follicle bursts, and a secondary oocyte is released into the abdominal cavity and taken up by the fallopian tube.
What happens in the Luteal Phase of Menstruation?
After ovulation, LH will cause the burst follicle to form into the corpeus luteum, which secretes progesterone and some estrogen. These progesterone levels rise as the estrogen stays high. Progesterone negatively inhibits the hypothalamus even at high concentrations, so as the levels rise, eventually the hypothalamus is negatively inhibited and the levels of GnRH, FSH, and LH fall. This prevents the ovulation of multiple eggs.
What happens in the Menstruation stage of Menstruation?
If no implantation occurs, the levels of LH will fall. This causes the corpus luteum to cease production of progesterone, which weakens the integrity of the uterine lining and causes it to slough off. With the estrogen and progesterone levels low again, the block on GnRH is lifted and the cycle can begin again.
When does pregnancy occur?
Pregnancy occurs when the thickened endometrial lining established in the first three phases of the menstrual cycle is implanted with a blastocyst.
How does fertilization cause pregnancy?
The ferilized zygote travels through the fallopian tube where it develops into a blastocyst and implants in the thickened endometrial lining of the uterus. The implanted blastocyst secretes Human Chorionic Gonadoptropin (hCG) which mimics LH and maintains the corpus luteum so it can secrete progesterone and some estrogen. This allows the implanted blastocyte to grow, the placenta to eventually form, and a baby to be born.
What is a blastocyst?
A blastocyst is a developed zygote with a large fluid filled cavity. This zygote has undergone several rounds of replication and is ready to be implanted in the endometrium.
What is menopause?
Menopause is the process by which a woman’s ovaries become less sensitive to FSH and LH over time. This means less progesterone and estrogen are produced which results in ovarian atrophy and makes pregnancy impossible. Less progesterone and estrogen removes negative feedback on GnRH which means FSH and LH blood levels RiseThis usually occurs between the ages of 45 and 55.
What are somatic cells?
Somatic cells are every single cell in an organism other than reproductive cells.
What are gametes?
Gametes are the haploid sex cells. In males, these are sperm. In females, these are ova.
What is the basic timeline of menstruation?
Days 1 through 14, shedding of previous endometrium and follicular phase.
Day 14, LH spike and ovulation.
Days 14 - 28 Luteal Phase
What is the corpus luteum and what is its function?
After an egg bursts from a follicle, the burst follicle will turn into the corpus luteum. The corpus luteum’s job is to produce progesterone in reponse to Leutenizing hormone.
Which hormone is responsible for secondary sex characteristics in women?
Estrogen
