Physio of the Estrous Cycle

Question 1

Who is involved in the endocrine regulation of the estrous cycle?

Answer 1

Hypothalamus: GnRH
Hypophysis: FSH and LH
Ovaries: estradiol, progesterone, inhibin
Uterus: Prostaglandin PF2a

Question 2

What role does inhibin play in the estrous cycle?

Answer 2

Prevents the development of multiple follicles during ovulation. Only one follicle should ovulate.

Question 3

What is the follicle producing from the primary stage to the Graffian stage?

Answer 3

Estradiol

Question 4

What is the follicle producing after the Graffian stage (CH and CL)?

Answer 4

Progesterone

Question 5

Where in the ovaries are follicles found?

Answer 5

Cortex

Question 6

If ovulation without fertilization occurs, the uterus produces _____ to lyse the corpus luteum and begin another cycle.

Answer 6

Prostaglandin PGF2a

Question 7

What are the committed follicles?

Answer 7

Follicles from the resting pool that are activated to begin growing

Question 8

When is development of the follicle gonadotropin (FSH and LH) independent?

Answer 8

Up to the formation of the antrum.

• Independent: primordial, primary, secondary
• Responsive: preantral, antral

Question 9

Gonadotropin dependent stages of follicle development

Answer 9

Antral, Graffian, up until ovulation

Question 10

At what stage is the follicle most susceptible to atresia?

Answer 10

Preantral to early antral transition, during formation of the theca cell layer

Question 11

Features of the corpus hemorrhagicum

Answer 11

Immediately after ovulation
Antrum collapses
Low progesterone levels

*will see bloody discharge in cows

Question 12

Features of the corpus luteum

Answer 12

Theca interna and granulosa cells proliferate and differentiate into small and large luteal cells.

Progesterone levels increase

Large luteal cells also secrete oxytocin and relaxin

Question 13

Area of the brain responsible for regular pulses of GnRH

Answer 13

Tonic GnRH Center of the hypothalamus.

*affected by internal and external (melatonin) signals

Question 14

Area of the brain responsible for releasing bursts of GnRH to initiate ovulation.

Answer 14

Surge Center of the hypothalamus

• female brain only!
• w/out sufficient GnRH burst, surge of LH is not released and ovulation doesn’t occur

Question 15

Effects of estrogen during ovulation

Answer 15

Thickening vaginal mucosa
Mucus secretion
Epithelial mitosis (endometrium)
Increased secretory and ciliary beat activity
Endometrial edema
Myometrial activity
Estrous behavior

Question 16

Ovulation is initiated by a surge of ___, and then Theca interna cells begin to produce _______ rather than androstenedione.

Answer 16

LH, progesterone

Question 17

During ovulation, the corpus luteum secretes ______, which _____endometrial secretion, _____ myometrial activity, and primes the brain to enhance the effects of ______.

Answer 17

During ovulation, the corpus luteum secretes PROGESTERONE, which INCREASES endometrial secretion, REDUCES myometrial activity, and primes the brain to enhance the effects of ESTROGEN.

Question 18

If fertilization does not occur, the uterine endometrium produces ______, which is released into the ____ ____, enters the ____ ____, and is delivered to the ovary where it causes lysis of the ____ _____.

Answer 18

If fertilization does not occur, the uterine endometrium produces PGF2a, which is released into the UTERINE VEIN, enters the UTERINE ARTERY, and is delivered to the ovary where it causes lysis of the CORPUS LUTEUM.

Question 19

Luteolysis is _______ in ruminants and _____ in the mare and sow

Answer 19

ipsilateral, systemic

Question 20

Progesterone from the CL forms a negative feedback loop with the hypothalamus to ensure what?

Answer 20

Continued tonic release of LH from the adenohypophysis to support the CL until PGF2a causes CL regression

Question 21

Inhibin forms a negative feedback loop with the pituitary to regulate what?

Answer 21

FSH release

Question 22

Melatonin _____ GnRH release in short day breeders like small ruminants, and _____ GnRH release in long day breeders like horses.

Answer 22

Melatonin INCREASES GnRH release in short day breeders like small ruminants, and DECREASES GnRH release in long day breeders like horses.

Question 23

Definition of puberty

Answer 23

Age at which the body can produce adequate amounts of GnRH and respond to it.

• acquisition of capability of sexual repro
• production of gametes
• onset of cyclicity in females

Question 24

Sexual maturity differs from puberty and involves

Answer 24

Body growth and adequate size for pregnancy/delivery/lactation

Question 25

What’s up with the pulse generator in juveniles?

Answer 25

That boi is dormant

Question 26

What adipocyte hormone senses ideal body size and maturity, and helps mediate the onset of puberty?

Answer 26

Leptin

Question 27

For contraception, the most efficient place to regulate GnRH production is…

Answer 27

at the hypothalamus

Question 28

Human and primate contraception works by…

Answer 28

preventing development of pre-ovulatory follicles

Question 29

3 phases of the estrous cycle

Answer 29

Follicular/Proliferative
Luteal
Quiescent

Question 30

Polyestrous animal. Not season specific.

Answer 30

Cow

Question 31

Monoestrous animal. Not season specific.

Answer 31

Dog

Question 32

Animals that are seasonally polyestrous

Answer 32

Horse

Sheep

Question 33

This phase of the ovarian cycle is estrogen dominated, includes proestrus and estrus, and involves development of follicles

Answer 33

Follicular/Proliferative

Question 34

This phase of the ovarian cycle takes place from ovulation to CL regression and is progesterone dominated.

Answer 34

Luteal/Secretory