Chapter 2.3

Question 1

What is the path an egg takes in the female reproductive system?

Answer 1

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.

Question 2

What is oogenesis?

Answer 2

Oogenesis refers to the production of female gametocytes, otherwise known as ova or eggs.

Question 3

In what 3 ways are oogenesis different than spermatogenesis?

Answer 3

1. 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.
2. 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.
3. Oogenesis halts secondary oocytes at Metaphase II. The secondary oocyte will wait to be fertilized before completing Meiosis II.

Question 4

What is a menarche?

Answer 4

Menarche is the term used to refer to a woman’s first menstrual cycle

Question 5

What is the menstrual cycle?

Answer 5

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.

Question 6

What is a polar body?

Answer 6

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.

Question 7

What are the two layer surrounding Oocytes?

Answer 7

1. The zona pellucida
2. Corona radiata

Question 8

What is the structure and function of the zona pellucida?

Answer 8

The zona pellucida is an acellular mixture of glycoproteins that protect the oocyte and allow sperm to bind to the oocyte.

Question 9

What is the structure and function of the corona radiata?

Answer 9

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.

Question 10

What is a zygote?

Answer 10

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.

Question 11

Describe the relative contribution of organelles and cytoplasm to the zygote made by a sperm and an ovum

Answer 11

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.

Question 12

From whom do we inherit our mitochondria and why?

Answer 12

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.

Question 13

In what way does FSH affect the testes?

Answer 13

FSH causes the Sertoli Cells to trigger sperm maturation.

MNEMONIC: Follicle Stimulating hormone Stimulates the Synthesis of Sperm by the Sertoli Cells

Question 14

In what way does LH affect the testes?

Answer 14

LH causes the interstitial cells aka Leydig cells of the testes to produce testosterone.

MNEMONIC: LH -> Low Hair -> Side effect of too much testosterone.

Question 15

What is GnRH?

Answer 15

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.

Question 16

How does the presence of GnRH change as we mature?

Answer 16

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.

Question 17

What are primary sex characteristics?

Answer 17

Primary sex characteristics are the sex organs with which you were born that developed during fetal development.

Question 18

What are secondary sex characteristics?

Answer 18

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.

Question 19

Which hormone is responsible for the secondary sex characteristics in men?

Answer 19

Testosterone

Question 20

What two hormones do the ovaries produce?

Answer 20

Estrogen and progesterone

Question 21

What 3 things does Estrogen do in females?

Answer 21

1. Estrogens result in the development of secondary sex characteristics for adult females.
2. In the embryo, estrogen stimulates the development of the female reproductive track.
3. Finally, estrogens also lead to the initial thickening of the endometrium each month in preparation for implantation of a zygote.

Question 22

What is the endometrium?

Answer 22

The endometrium is the inner lining of the uterus.

Question 23

What are the 2 functions of the endometrium?

Answer 23

1. In day to day life, the endometrium keeps adjacent walls of the uterus from sticking together, thereby maintainign its patency.
2. 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.

Question 24

In what way does FSH affect the ovaries?

Answer 24

FSH stimulates the growth of the follicles in the ovaries.

Question 25

In what 2 ways does LH affect the ovaries?

Answer 25

A sharp spike in LH during menstruation causes ovulation. After ovulation, LH stimulates the corpus luteum to secrete progesterone

Question 26

What is the function of progesterone?

Answer 26

1. Progesterone contributes to the development and maintenance of the endometrium, but not its original thickening (That's estrogen's job!)

Question 27

What are the 4 stages of menstruation?

Answer 27

1. Follicular Phase 2. Ovulation 3. Luteal Phase 4. Menstruation

Question 28

What occurs in the Follicular Phase of Menstruation?

Answer 28

The follicular phase begins when the uterine lining of the previous cycle begins to shed. 1. As Estrogen and Progesterone fall in response to the death of the corpus luteum, GnRH is secreted in response. 2. GnRH secretion leads to the rise of FSH and LH. 3. FSH and LH work together to cause the follicles in the ovary to grow (Mostly FSH though) 4. 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. 5. The estrogen that has been released gets to work on re-thickening the endometrium (decidua).

Question 29

What occurs in Ovulation?

Answer 29

1. 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. 2. This increase in GnRH by the hypothalamus leads to a spike in FSH and LH levels. 3. The spike in LH levels induces ovulation.

Question 30

What is ovulation?

Answer 30

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.

Question 31

What happens in the Luteal Phase of Menstruation?

Answer 31

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.

Question 32

What happens in the Menstruation stage of Menstruation?

Answer 32

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.

Question 33

When does pregnancy occur?

Answer 33

Pregnancy occurs when the thickened endometrial lining established in the first three phases of the menstrual cycle is implanted with a blastocyst.

Question 34

How does fertilization cause pregnancy?

Answer 34

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.

Question 35

What is a blastocyst?

Answer 35

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.

Question 36

What is menopause?

Answer 36

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.

Question 37

What are somatic cells?

Answer 37

Somatic cells are every single cell in an organism other than reproductive cells.

Question 38

What are gametes?

Answer 38

Gametes are the haploid sex cells. In males, these are sperm. In females, these are ova.

Question 39

What is the basic timeline of menstruation?

Answer 39

Days 1 through 14, shedding of previous endometrium and follicular phase. Day 14, LH spike and ovulation. Days 14 - 28 Luteal Phase

Question 40

What is the corpus luteum and what is its function?

Answer 40

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.

Question 41

Which hormone is responsible for secondary sex characteristics in women?

Answer 41

Estrogen