Endo V

Question 1

Day 1 of the menstrual cycle begins with […]

Answer 1

detectable vaginal bleeding due to the deterioration of the uterine endometrium

Question 2

What happens prior to day 1 of the menstrual cycle in the uterine lining? Include the hormones involved.

Answer 2

Prior to day one, endometrium thickens under influence of estradiol.
Progesterone induces the appearance of specialized glycogen-secreting glands.

Question 3

What prompts the start of the menstrual cycle?

Answer 3

Menses (bleeding) begins when estradiol and progesterone very low in circulation, when the blood vessels supplying endometrium constrict, reducing blood supply. The endometrium then deteriorates, flows through the cervix into the vagina.

Question 4

Name the major stages of the menstrual cycle.

Answer 4

3 stages: menstrual, proliferative, and secretory
Follicular phase = menstrual and proliferative (days 1-14)
Luteal phase = secretory (days 14-28)

Question 5

Describe the hormonal process involved in the transition from one menstrual cycle to the next.

Answer 5

When estrogen and progesterone drop as a result of the corpus luteum degrading, pituitary FSH secretion increases. Inhibin, which inhibits secretion of FSH, also drops, contributing to the elevation in FSH release. This FSH causes the next cohort of ovarian follicles to develop.

Question 6

The proliferation of follicles due to FSH leads to the production of […], which has the effect of […]

Answer 6

estrogen, further stimulating granulosa cell profileration

Question 7

What happens around day 8 of the menstrual cycle?

Answer 7

One follicle becomes dominant and committed to further development. Remaining follicles begin to degenerate by atresia. In humans, how one follicle becomes dominant is still unknown.

Question 8

Once the dominant follicle has committed, it produces […], which is important later in the cycle in […]

Answer 8

Estradiol, stimulating uterine endometrium proliferation

Question 9

What is happening in the menstrual cycle on day 13 to the endometrium? Include the hormones involved.

Answer 9

The endometrium is very thick. Estradiol induces production of endometrial progesterone receptors.

Question 10

What is the effect of moderate estradiol concentrations on the brain and pituitary?

Answer 10

• Has a negative feedback on FSH release
• Stimulates the synthesis of LH by pituitary and increases the sensitivity of the pituitary to GnRH, which further stimulates LH synthesis.
• Inhibit LH release from pituitary despite more synthesis, causing accumulation in pituitary.

Question 11

What causes estradiol concentrations to rise throughout the menstrual cycle?

Answer 11

The development of the dominant follicle.

Question 12

Describe the effects of high estradiol concentrations on the brain and pituitary.

Answer 12

• Stimulates LH release, causing an LH surge (due to accumulation of LH from lower estradiol concentrations)
• Also stimulates LH synthesis
• Increased sensitivity of the anterior pituitary to GnRH, leading to LH synthesis

Question 13

What is the estrogen positive feedback control?

Answer 13

High levels of estrogen increase sensitivity of anterior pituitary cells to GnRH and increase LH synthesis.

Question 14

What is the LH surge? When does this occur in the menstrual cycle? What is its effect?

Answer 14

The LH surge occurs when high levels of estradiol concentrations cause the release of LH from the anterior pituitary. This occurs around halfway through the menstrual cycle, on day 14. Its effect its to cause ovulation, as it causes the follicle to rupture and the ovum to be ejected.

The LH surge is also accompanied by a smaller surge in FSH

Question 15

Describe how estrogen and progesterone vary throughout the menstrual cycle.

Answer 15

Estrogen starts at medium concentrations peaks at the start of the luteal phase and the has a second, smaller peak towards the end of the luteal phase.

There is no progesterone until the luteal phase. The peak occurs towards the end of the luteal phase.

Question 16

Draw and describe the feedback mechanism of steroid hormones on gonadotropin action for the female reproductive system at moderate amounts of estrogen.

Answer 16

• Hypothalamus releases GnRH
• Anterior pituitary releases FSH and LH
• FSH activates granulosa cells, which secrete inhibin that has a negative feedback on FSH.
• LH activates theca cells, which secrete androgens (which get converted to estrogen).
• Estrogen has a negative feedback on GnRH, LH, and FSH

Question 17

Draw and describe the feedback mechanism of steroid hormones on gonadotropin action for the female reproductive system at high amounts of estrogen.

Answer 17

• Hypothalamus releases GnRH
• Anterior pituitary released LH (LH surge)
• Large amounts of estrogen generated, which has a positive feedback on GnRH and LH.

Question 18

Explain how female oral contraceptives work.

Answer 18

Pills contain estrogen and progesterone. They maintain moderate circulating levels of estrogen and progesterone, which suppresses the release of LH and FSH from the pituitary and prevent ovarian follicles from maturing and being ovulated.

Question 19

How does the corpus luteum change under the influence of LH?

Answer 19

Under the influence of LH, the follicle becomes the corpus luteum - produces large amounts of estradiol and progesterone to induce growth of the uterus. In addition, under the influence of progesterone the endometrium becomes glandular.

The endometrium is now fully prepared to receive and support the development of a growing embryo.

Question 20

What happens during the luteal phase in the case of no fertilization? What happens after?

Answer 20

The egg degenerates and the corpus luteum degenerates as well (luteolysis). During this time, the steroids produced by the corpus luteum dominate. After the 14 days of the luteal phase, the steroid levels drop and the period begins. The pituitary increases its secretion of FSH in response and the cycle starts again.

Question 21

At ovulation, the unfertilized egg is taken by the […] and is propelled towards the […]

Answer 21

fimbria of the oviduct, lumen of the uterus

Question 22

Where does fertilization of the egg take place? When during the cycle must this occur?

Answer 22

Spermatozoa can travel as far as the oviduct to fertilize the egg. This occurs during ovulation.

Question 23

How does the size of the egg change after fertilization?

Answer 23

The egg doesn’t change in size, it just becomes more specialized via differentiation.

Question 24

The fertilized egg first differentiates into the […]. This occurs when […]

Answer 24

blastocyst, it is being transported down the oviduct to the uterine lumen

Question 25

The blastocyst differentiates into what components? What do they become?

Answer 25

The blastocysts differentiate into a trophoblast, which becomes the placenta and embeds the embryo into the uterine lining, and the inner cell mass, which becomes the embryo.

Question 26

Around the time of implantation, what is released by the fertilized egg, and by what part of the egg? What is its function?

Answer 26

Around the time of implantation, trophoblast starts to synthesize HCG, which has LH-like properties and stimulates the corpus luteum to continue secreting estrogen and progesterone.

Question 27

At what point in pregnancy does endocrine function of the corpus luteum get taken over? What takes it over?

Answer 27

This occurs after the 12th week of pregnancy. The function of the corpus luteum (secretion of progesterone and estrogen) gets taken over by the placenta.

Question 28

What is the fetoplacental unit?

Answer 28

It is made up of the placenta and the developing fetus.

Question 29

How do HCG, estrogen, and progesterone levels vary through pregnancy up to delivery?

Answer 29

• HCG peaks around months 1-2 of pregnancy and then remains low.
• Estrogen steadily rises and drops suddenly after delivery.
• Progesterone follows the same pattern but doesn’t rise as high as estrogen.

Question 30

The basis of the biological or immunological pregancy test is […]

Answer 30

HCG hormone

Question 31

Describe the breast ducts before pregnancy.

Answer 31

Under the action of estrogens, there is duct growth during puberty and duct branching but few alveoli.

Question 32

How does the inner structure of the breast change throughout pregnancy and after? Explain why.

Answer 32

Throughout pregnancy, the release of progesterone stimulates the growth of alveoli. The alveoli grow larger and development a lumen in mid-pregnancy. Lactation causes the alveoli to dilate. After pregnancy and lactation, the glands regress.

Question 33

What is the main cause of breast enlargement during pregnancy?

Answer 33

Although mammary ducts and their alveoli do contribute, most breast enlargement is due to fat deposition under the glandular tissue.

Question 34

Mammary ductal and alveoli structures develop under the influence of hormones […]

Answer 34

Estrogen, progesterone, prolactin, and human placental lactogen

Question 35

Milk production during pregnancy is controlled by what hormone(s)? Explain how.

Answer 35

Milk production during pregnancy are controlled by prolactin, but high estrogen levels inhibit secretion of prolactin.

Estrogen levels are high during pregnancy because we don’t want milk secretion to occur. This is also why E and P levels drop so quickly after delivery.

Question 36

After parturition, how do estrogen and prolactin levels change?

Answer 36

Levels of estrogen decrease and prolactin remains high. The decrease in estrogen allows for secretion of milk.

Question 37

What are the two hormones that mainly affect nursing? Explain how and where they are produced.

Answer 37

Nursing: under action of oxytocin, ducts contact to cause milk ejection.
Prolactin: milk production.

Question 38

What are the typical components of breast milk?

Answer 38

Milk: water protein, fat, carbohydrate lactose, and antibodies. Infectious agents such as viruses and drugs may also be transmitted from mother to infant through breast milk.

Question 39

What is lactational amenorrhea?

Answer 39

Maintained nursing stimulates prolactin, which inhibits secretion of FSH and LH. This blocks the resumption of the reproductive cycle. Nursing used to be used as a natural method of contraception, but it requires frequent suckling.

Question 40

What is menopause?

Answer 40

It is the loss of ovarian steroid production (estrogen and progesterone) at the end of the reproductive period. By this point, most ovarian follicles have disappeared by atresia and others have been ovulated. This cessation of steroid hormone productions eliminates the negative feedback loop and causes a rise in FSH and LH.

Question 41

What are the typical symptoms of menopause?

Answer 41

Lack of estrogens often induces hot flashes, dry vagina, restlessness, bone loss (osteoporosis), etc.

Question 42

Can menopause be treated? Explain.

Answer 42

Symptoms can be treated by estrogen replacement therapy, but since follicular depletion is the primary cause of menopause, fertility cannot be restored.

Question 43

Where can 1,25 vitamin D production take place? What controls this production?

Answer 43

Although traditionally, it was believed that this only took place in the kidney, it is now known that most cell types in the peripheral tissues of the body (including the skin) also have the necessary enzyme to do this.

In the kidney, this process is controlled by PTH. Elsewhere, it is controlled by immune cells.

Question 44

What conditions are required for UVB light to be able to contribute to vitamin D production?

Answer 44

The sun has to be over 45 degrees in the sky such that the path through the ozone layer is direct enough that UVB can still penetrate.

Question 45

What is vitamin D winter? What factors is it affected by?

Answer 45

Vitamin D winter is the period during which you can’t make vitamin D via sun exposure. This can be affected by latitude (vitamin D sufficient all year near equator and gets worse towards poles), altitude, and cloud cover.

Question 46

How does skin colour affect the levels of 25-hydroxy vitamin D?

Answer 46

The lightest skin type produces 6X more vitamin D for a given dose of UV light than the darkest skin type.

Question 47

What is the major circulating form of vitamin D?

Answer 47

25-hydroxy-vitamin D3

Question 48

What are the 3 types of diseases that have north-south gradients? What do they all have in common?

Answer 48

1. Certain types of cancers (in particular digestive cancers and leukemias)
2. Autoimmune diseases such as multiple sclerosis
3. Infectious diseases

They are all linked to vitamin D, whose availability varies with latitude due to vitamin D winter.

Question 49

Explain how cells of the immune system respond to vitamin D to fight off infection.

Answer 49

Cells of the immune system have been shown to become responsive to 25D3 after sensing the presence of bacterial cell wall components. They start expressing the 1-hydroxylase enzyme, increasing conversion by the immune system of 25-D3 to 1,25-D3 to fight off infection.

Question 50

How does the treatment of cells with 1,25-D3 affect their ability to fight infection?

Answer 50

It induces an antimicrobial response werein they create antimicrobial proteins.

Question 51

How does the stimulation of antimicrobial peptide gene transcription by serum vary between African american and caucasian americans? Why?

Answer 51

It is much higher in caucasians because the levels of 25-D3 are so much higher. So, vitamin D deficiency does make a difference in antimicrobial response.

Question 52

In the female reproductive system, FSH activates […] cells and LH activates […] cells. State what else these cells types release.

Answer 52

Granulosa, theca.
Granulosa: inhibin
Theca: androgen (which get converted to estrogen)