MNSR 44 - Hormones of the Gonads, Oestrus and Menstrual Cycles

Question 1

what do gonads produce

Answer 1

produce different types of hormones and gametes

Question 2

the sex hormones are all -1. __ based 2.___

Answer 2

1. cholesterol

2. steroids

Question 3

how many carbon atoms does cholesterol have

Answer 3

27 carbon atoms

Question 4

production of steroid from cholesterol

Answer 4

removes 6 terminal carbons -> 21 carbon intermediate called pregnenolone
pregnenolone converted into active sex steroids

Question 5

3 types of carbon sex steroids

Answer 5

1. The C-21 Steroids: Progestogens, Cortisol, Aldosterone
2. The C-19 Steroids: Androgens
3. The C-18 Steroids: Estrogens

Question 6

androgens

Answer 6

hormones released from testes

Question 7

where is 95% of circulating testosterone produced

Answer 7

in leydig cells

Question 8

At puberty, under the influence of 1. ___, the 2. ___
begin to secrete 3.___ and continue to do so during
reproductive life though reaching a peak at about 4.___ years

Answer 8

1. pituitary LH
2. interstitial cells
3. testosterone
4. 20

Question 9

function of testosterone

Answer 9

1. Maintenance of the male ducts and glands
2. Stimulate and support spermatogenesis
3. Induce and maintain the male secondary sexual characteristics
4. Anabolic effects - muscle build-up, nitrogen retention, male shape
5. During fetal life from the 7th week small quantities are produced by the testes which differentiate male ducts and organs.

Question 10

menstrual cycle

Answer 10

phenomenon of blood loss as a result of degradation of endometrium where the ovum is not fertilised only found in higher primates

Question 11

how do mammals not experience blood loss at the end of the oestrous cycle

Answer 11

most mammals reabsorb the endometrial lining and do

not experience a loss of blood at the end of the oestrous cycle

Question 12

what cells does follicle stimulating hormone stimulate

Answer 12

sertoli cell

Question 13

what is the FSH promoting when stimulating sertoili cells

Answer 13

promotes spermatogenesis

and induce secretion of androgen binding protein (concentrates testosterone in seminiferous tubules)

Question 14

What is the physiological response and result when hypothalamus secretes gonadotrophin-releasing hormone

Answer 14

Increase secretion of FSH and decrease secretion of LH in anterior pituitary
Stimulates spermatogenesis and inhibin secretion to provide negative feedback to stop FSH secretion
Decrease of LH increases release of testosterone in leydig cells which provides negative feedback for LH and stops LH secretion and testosterone is released in blood stream

Question 15

2 groups that the hormones released from ovaries fall in

Answer 15

estrogens and progestagens

Question 16

what hormones control estrogens and progestagens

Answer 16

FSH and LH

Question 17

3 significant estrogens

Answer 17

Eestradiol-17
Estriol
Estrone

Question 18

Estradiol-17

Answer 18

most active and abundant in women

produced by granulosa cells in developing ovarian follicle

Question 19

Estriol

Answer 19

produced in large amounts by placenta in pregnant women

Question 20

Estrone

Answer 20

main estrogen for post-menopausal women

produced in peripheral tissue esp. adipose tissue

Question 21

androstenedione can be converted estrone with the help of what enzyme

Answer 21

aromatase

Question 22

testosterone can be converted to estradiol with the help of what enzyme

Answer 22

aromatase

Question 23

estrogen function

Answer 23

maintenance of female ducts - inc. division of vaginal epithelium and uterine endometrium
induce and maintain female secondary sexual characteristics
other physiological effects - bone density, liver, cardiac and cognitive function

Question 24

name the most active progestogen hormone

Answer 24

progesterone

Question 25

where and when is progesterone secreted

Answer 25

secreted by cells of corpus luteum and placenta during pregnancy

Question 26

progesterone function

Answer 26

prepare uterine endometrium for implantation
stimulate growth of secretory alveoli in mammary glands for milk production but inhibit lactation during pregnancy
reduce uterine smooth muscle sensitivity to oxytocin

Question 27

oestrous cycle

Answer 27

period in time in which female will become sexually receptive to male within the same frame as ovulation this is controlled by endocrine system

Question 28

oestrus

Answer 28

drive to mate

Question 29

anoestrus

Answer 29

will not mate

Question 30

polyoestrous

Answer 30

mammals that display a succession of oestrous cycles e.g. domesticated animals and rodents

Question 31

monoestrous

Answer 31

only breed at a certain time of the year e.g. carnivores

Question 32

monthly menstrual fluid loss

Answer 32

50-100ml

Question 33

follicular phase of menstrual cycle

Answer 33

follicle develops
controlled by estrogen under control of FSH and LH
Ends at ovulation

Question 34

Luteal phase of menstrual cycle

Answer 34

begins after ovulation
corpus luteum develops from ovarian follicle and secretes progesterone
phase ends when drop in progesterone trigger menstruation and begin next cycle

Question 35

endocrinology of follicular phase

Answer 35

1. before menstruation - high levels of estrogen and progesterone from corpus luteum suppress prod. FSH and LH
2. Break down of corpus luteum - drop in progesterone and estradiol-17 - triggers menstruation and stops negative feedback of FSH and LH
3. Hypothalamus release Gonadotrophin-Releasing Hormone (GnRH) and FSH and LH from anterior pituitary gland are released and 6-12 primary follicles in ovaries enlarge into secondary follicles
4. LH and FSH induce secondary follicles to secrete estradiol-17
5. Estrogen trigger regrowth of endometrial lining
6. Estrogen inhibits GnRH, causing FSH and LH levels to drop
7. Reduced FSH and LH cause most follicles to die

Question 36

Endocrinology of ovulation

Answer 36

1. peak of LH cause lutenization of membrana granulosa cells of follicle becoming corpus luteum
2. body grows for 7-8 days after ovulation producing large quantities of progesterone and estradiol-17 -> inhibit the hypothalamus and pituitary gland LH and FSH
3. High levels of progesterone during luteal phase of cycle cause endometrium to further proliferate
4. if fertilisation doesn’t occur corpus luteum regresses by day 26 of cycle
5. leads to drop in progesterone and estradiol-17 - causes constriction in spiral arteries in endometrium and breaks down
6. Drop in progesterone and estrogen stops negative inhibition of FSH and LH from hypothalamus and anterior pituitary - rise start next cycle,

Question 37

endocrinology of pregnancy

Answer 37

1. if fertilization occurs blastocyst is implanted on endometrial wall for 6-7 days
2. must maintain corpus luteum until placenta over 6th week
3. Blastocyst secretes Human Chronic Gonadotrohpin (HCG) - maintains corpus luteum and steady increase estrogen and progesterone
4. After 60 days HCG levels drop to low levels for rest of pregnancy by estrogen and progesterone levels remain high as they are now produced by placenta reach 10X and 200X those of luteal phase
5. Human Placental Lactogen (HPL) is release has growth hormone and prolactin like properties
6. Labour occurs contraction of smooth muscles of myometrium at ~280 days/9 months