Reproductive Cycles

Question 1

when does the reproductive cycle occur?

Answer 1

between periods of sexual receptivity (estrus or heat) and/or ovulations

Question 2

types of reproductive cycles

Answer 2

estrous cycle (domestic animals)
menstrual cycle (primates)
ovulatory cycle (birds)

Question 3

types of estrous cycles

Answer 3

• Polyestrous
• Seasonally polyestrous
• monoestrus

Question 4

polyestrous cycle

Answer 4

• uniform distribution of estrous cycle throughout the year

Question 5

seasonally polyestrous cycle

Answer 5

clusters of estrous cycle that occur only during a certain season of the year

Question 6

monoestrus cycle

Answer 6

having only one cycle per year

Question 7

phases of estrus cycle

Answer 7

follicular and luteal

Question 8

follicular phase is characterized by

Answer 8

1) development of follicle
2) ovulation

Question 9

luteal phase is characterized by

Answer 9

formation and function of corpus luteum

Question 10

Hormonal Regulation of Estrous Cycle (4 steps)

Answer 10

1) Hypothalamus releases GnRH
2) Pituitary releases FSH and LH
3) Ovary releases estrogen and progesterone
4) Estrogen and progesterone enter reproductive tract

Question 11

Describe the Events Ocurring During the Follicular Phase

Answer 11

1) steady release of GnRH from the tonic center of the hypothalamus
2) GnRH acts of gonadotrophs of the anterior pituitary to secrete gonadotropins- FSH and LH
3) FSH and LH act on ovary, induce follicular development and maturation
4) Low level of estradiol from the follicle exerts negative feedback on hypothalamus and pituitary to reduce FSH secretion
5) High levels of estradiol exerts positive feedback on the surge center resulting in the preovulatory surge of LH

Question 12

Ovulation is caused by ____ and results in ____

Answer 12

caused by: preovulatory surge of LH acting on the follicle

results in: rupture and release of oocyte

Question 13

Events Occuring at Luteal Phase

Answer 13

1) Formationand maturation of corpus luteum
2) High progesterone (secreted by mature CL) suppress FSH and LH synthesis (negative feedback)
3) Regression of corpus luteum (luteolysis)
4) Progesterone secretion decreases

5) Release of negative feedback of progesterone on hypothalamus and pituitary

Question 14

proestrus is _ begins when ___

Answer 14

Period before estrus
Begins when progesterone declines as a result of luteolysis/ destruction of the corpus lutem (from the previous estrus)

Question 15

proestrus is characterized by ____ this is due to _____

Answer 15

shift from progesterone dominance to estradiol dominance, due to FSH and LH

Question 16

During Proestrus, the increased secretion of _____ causes what changes?

Answer 16

The increased secretion of estradiol causes:
- ovulatory follicles to mature in preperation for ovulation
- reproductive system to prepare for estrus and mating

Question 17

What is the most recognizable stage of the estrus cycle, characterized by visible behavioral symptoms such as sexual receptivity, female allows copulation?

Answer 17

estrus

Question 18

What is the most dominant hormone during estrus?

Answer 18

estradiol, which both changes behavior and causes major physiological changes in reproductive tract

Question 19

Signs of estrus

Answer 19

increased locomotion, phonation (vocal expression), nervousness, attempts to mount other animals

Question 20

Standing estrus is the

Answer 20

willingness of female to accept male for mating

Question 21

Lordosis

Answer 21

characteristic arching of the back in preparation for mating

Question 22

During Metestrus

Answer 22

1) transition from estradiol dominance to **progesterone dominance **
2) ovulation (release of egg from ovaries)
3) Corpora lutea becomes fully functional (due to the cellular and structural remodeling of the ovarian follicle)

Question 23

Diestrus is the

Answer 23

Longest stage of the estrous cycle
and the period of maximum luteal function

Question 24

during diestrus

Answer 24

• High progesterone secretion prompts the uterus to prepare a suitable environment for embryo implantation and successful pregnancy
• Ends when the CL is lysed (luteolysis)

Question 25

diestrus is characteriszed by

Answer 25

the substained secretion of progesterone (high amounts of progesterone)

Question 26

the luteal phase includes

Answer 26

metestrus and diestrus

Question 27

what is the major ovarian structure of the follicular phase?

Answer 27

the follicle

Question 28

what is the major ovarian structure of the luteal phase?

Answer 28

the corpus luteum

Question 29

what is the major hormone of the follicular phase?

Answer 29

estradiol

Question 30

what is the major hormone of the luteal phase?

Answer 30

progesterone

Question 31

sexual receptivity occurs in what stage

Answer 31

the follicular phase, not the luteal

Question 32

Changes in OVIDUCT due to estradiol and progesterone

Answer 32

Estradiol - Increase in: spontaneous muscular activity, fluid secretion, epithelial cell height - Ciliation of epithelial cells Progesterone - Generally causes inactivity - Epithelial cells regress and atrophy (decreased cell height and partial de-ciliation) - Some mucous secretion

Question 33

Changes in UTERUS due to estradiol and progesterone

Answer 33

Estradiol - Preparation for transport and survival of spermatozoa - Congestion and edema of the uterine mucosa with mostly columnar epithelial cells - increase in epithelial, glandular, and stromal cell division - Sensitivity and amplitude of myometrial contractions (resulting in firm/erect uterus) - Infiltration of leucocytes Progesterone - High progesterone prompts the uterus to prepare a suitable environment - Reduced congestion and edema of the mucosa - Increased cell differentiation and glandular secretions (Histotroph-Uterine milk) - Flaccid uterus. Reduced myometrial tone (quiescence) Infiltration of leukocytes reduced

Question 34

Changes in CERVIX due to Estradiol and Progesterone

Answer 34

Estradiol - Relaxation of the cervical folds - Congestion and edema - Increased cell proliferation - Increase in secretion of mucus through vulva Progesterone - Cervical canal tightly closed - Reduced congestion and edema - Increased cell differentiation - Thick and tenacious mucus

Question 35

Changes in VAGINA due to estradiol and progesterone

Answer 35

Estradiol Congestion and edema Increased cell proliferation Keratinization of the epithelium Marked increase in the glandular secretion of the clear viscid mucus discharged through vulva Progesterone Reduced congestion and edema Increased cell differentiation Reduced keratinization Reduced secretions

Question 36

long photoperoid leads to

Answer 36

low melatonin

Question 37

Transition from anestrus to cylicity in ewe (during breeding season) is due to

Answer 37

- an increase in progesterone during the luteal phase of the estrus cycle - this enables the preovulatory GnRH surge

Question 38

in cats

Answer 38

the reproductive cycle continues unless there is mating, mating disrupts the cycle and is necessary for ovulation

Question 39

Vaginal Epithelial Changes in Bitch

Answer 39

Anestrus (A): vaginal epithelium is thin and underlying stroma is compact Proestrus (P): vagina becomes thicker and cornified, stroma and smooth muscle also start to thicken and there is both stromal congestion and edema Estrus (E): the vagina is thick and heavily cornified Diestrus (D): vagina is much thinner (three to four cell layers) and loses its cornification

Question 40

high/low hormones during diestrus

Answer 40

peak progesterone low estradiol, LH, and FSH

Question 41

high/low hormones during proestrus

Answer 41

progesterone decreasing estradiol increasing LH and FSH increasing

Question 42

high/low hormones during estrus

Answer 42

peak estradiol, LH, and FSH low progesterone

Question 43

high/low hormones during metestrus

Answer 43

increasing progesterone low estradiol, LH, and FSH