2.3 HY The Reproductive System

Question 1

What are the functions of the Leydig and Sertoli cells?

Answer 1

Sertoli Cells help to nourish the sperm produced in the seminiferous tubules.

The Leydig Cells produce testosterone.

Question 2

What phase of meiosis is the primary oocyte arrested?
In what phase of meiosis the secondary oocyte arrested?

Answer 2

Primary Oocyte Arrested: Meiosis 1, prophase I
Secondary Oocyte Arrested: meiosis 2, metaphase II

Question 3

What is the acrosome?
What organelle forms the acrosome?

Answer 3

Acrosome- cap over the head of the sperm. It is made from the golgi apparatus and necessary to penetrate the ovum.

Question 4

What hormones are key to sexual differentiation in a fetus with XY genotype? Describe the expected phenotype if receptors to these hormones are abscent.

Answer 4

Testosterone: men
Estrogen: women

Since these receptors are absent, the offspring will appear the opposite sex.

Question 5

What are the four phases of the menstrual cycle?

What are the features and the relative hormone concentrations at each phase?

Answer 5

Question 6

Which chromosome is sex determined by?

Answer 6

23rd pair.

Question 7

What does hemizygous mean with respect to men and chromosomes?

Answer 7

Women have two copies of X. i.e. they are XX. So they have a problem with one X, the other X can usually compensate.

However in men, they have X and Y. Therefore, there is no other X that can compensate. They are said to be hemizygous

Therefore, women express sex-linked disorders much less than males.

Question 8

What carries more information? X chromosomes or Y chromosomes?

Answer 8

X chromosome carries most information.

However, on the Y chromosome, there is a gene called the SRY (sex-determining region Y) which codes for transcription factors that initiates testis differentiation, and the formation of male sex organs.

Question 9

What is the pathway of the sperm through the male reproductive tract? What is the acronym?

Answer 9

SEVE(N) UP

Seminiferous tubules
Epididymis
Vas Deferens
Ejaculatory Duct
(n/a- nothing)
Urethra
Penis

Question 10

What parts of the male reproductive tract produce seminal fluid? (x3)

Answer 10

Seminal vesicles- nourish sperm with fructose
Prostate Gland - mildly alkaline properties, so sperm can live in the relative acidity of the female reproductive tract
Bulbourethral gland - produce a clear viscous fluid that cleans out any remnants of urine and lubricates the uretra during sexual arousal.

Question 11

What is semen?

Answer 11

The combination of sperm and seminal fluid.

Question 12

What are the steps of spermatogenesis, or the formation of sperm?

Answer 12

Spermatagonia - diploid stem cells
Primary Spermatocytes- occurs after they replicate their genetic material (s-phase of cell cycle).
Secondary Spermatocytes-occur after the first meiotic division, resulting in the haploids
Spermatids- occur after meiosis II, generate haploid spermatids.
Spermatozoa- mature sperm after maturation.

Question 13

How many spermies do each spermatagonia create?

Answer 13

4. 1 diploid cell becomes four haploid cell/ spermatozoa.

Question 14

What are follicles?

Answer 14

Multilayered sacs in the ovaries that nourish and protect immature ova (eggs)

Internet: Ovarian follicles are small sacs filled with fluid that are found inside a woman’s ovaries. They secrete hormones which influence stages of the menstrual cycle and women begin puberty with about 300,000 to 400,000 of them. Each has the potential to release an egg for fertilization.

Question 15

What is the difference between vagina and vulva?

Answer 15

Vulva- outer genitals
Vagina- inner canal

Question 16

What is oogenesis?

Answer 16

The production of female gametes.

Question 17

What are primary oocytes?

Answer 17

these are all of the oogonia that have already undergone DNA replication.
They are 2n, like primary spermatocytes,
They are arrested in Prophase 1.

Question 18

What is the secondary oocytes and the polar body?

Answer 18

The secondary oocytes is the part that receives most of the cytoplasm in division. The polar body receives nearly none. It remains arrested in metaphase II and does not complete the remainder of meiosis II unless fertilization occurs.

the polar body generally does not divide any further and will never produce functional gametes.

Question 19

What are the two zones that surround the oocyte?

Answer 19

Zona pellucida- surrounds the oocyte itself and is the acellular mixture of glycoproteins that protects the oocyte and contains compounds necessary for sperm cell binding.

Corona Radiata- lies outside the zona pellucida, and is a layer of cells that adhere to the oocyte during ovulation.

Question 20

What happens if the egg is fertilized?

Answer 20

It will trigger the secondary oocyte to to finish meiotic division and split into a mature ovum and another polar body (which will be broken down).

The egg contributes all of the cytoplasm, organelle (including mitochondria), and RNA.

Question 21

What is a zygote?

Answer 21

Is the cell that is formed, which is now a diploid, when the sperm and the egg fuse.

Question 22

Walk through the hormones that lead to sexual development? What are they, where do they come from?

HPA Axis

Answer 22

Hypothalamus- releases GnRH that go to anterior pituitary
Anterior Pituitary- releases FSH and LH

Causes the production of sex hormones

Question 23

In men, what does FSH and LH work on to do what?

Answer 23

FSH= sertoli cells for sperm maturation
LH= interstitial cells for testosterone

Both FSH and Sertoli have ‘S’ for Sperm

Question 24

In women, what does the FSH result in?

Answer 24

Results in the production of estrogen.
This results in the thickening of the uterus (endometrium) in preparation for implantation of the zygote.

Estrogen Establish the endometrium
Progesterone Protects the endometrium.

Question 25

In women, what does LH do? Where does it act?

Answer 25

LH causes the **corpus luteum** to secrete progesterone. Progesterone is associated with the development and maintenance of the endometrium, but **not** the initial part. Initially, estrogen influences this. By the end of the first trimester, progesterone supplies the placenta, and the corpus luteum dies out.

Question 26

What are the four phases of the menstrual cycle?

Answer 26

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

Question 27

What starts the follicular phase?

Answer 27

Menstrual flow, the uterine lining sheds. Because the estrogen and progestogen fall, the GnRH increases production, causing increased LH and FSH. The LH and FSH cause the follicle to produce estrogen, which in turn reduces GnRH, LH and FSH via a negative feed back loop. This estrogen gets the endometrium started again.

Question 28

What happens in ovulation?

Answer 28

there is a paradoxical change in the way the GnRH, LH, and FSH react to estrogen produced by the follicle. Once it reaches a high enough level, LH and FSH start to spike. The LH induces ovulation: releasing the ovum from the ovary into the abdominal cavity

Question 29

What happens in the Luteal Phase?

Answer 29

LH causes the ruptured follicle to **form** the **corpus luteum**, which secretes **progesterone**. The progesterone propagates the **endometrial lining**. With the increase of progesterone results in the reduction of GnRH, FSH, and LH, preventing ovulation of multiple eggs.

Question 30

What happens if implantation does not occur?

Answer 30

The corpus luteum looses stimulation from LH, and progestone declines, and menstruation occurs.

Question 31

What happens if implantation occurs?

Answer 31

The zygote will develop into a **blastocyst** and secrete **hCG**, which is very similar to LH, which maintains the corpus luteum. This is important because it keeps the Estrogen and progestogen secreted by the corpus luteum going, thereby keeping the uterine lining in place. Later, in the second semester, hCG levels decline because the placenta has grown to a sufficient size to secrete enough progesterone and estrogen itself, which continue to serve as a negative feedback loop for GnRH secretion.