Lecture 27 3/22/24

Question 1

What is the estrous cycle?

Answer 1

interval between two ovulations

Question 2

What are the phases of the estrous cycle, based on dominant structure?

Answer 2

-follicular phase
-luteal phase

Question 3

What are the primary behavioral events during estrus?

Answer 3

-sexual receptivity
-copulation

Question 4

What are the characteristics of the follicular phase?

Answer 4

-period from regression of CL to ovulation
-relatively short
-primary structures are growing dominant follicles
-follicles produce estradiol

Question 5

What are the characteristics of the luteal phase?

Answer 5

-period from ovulation until CL regression
-longer phase
-dominant structure is corpora lutea
-CL produces progesterone

Question 6

What are the stages of the estrous cycle?

Answer 6

-proestrus
-estrus
-metestrus
-diestrus

Question 7

Which stages occur during the follicular phase?

Answer 7

-proestrus
-estrus

Question 8

Which stages occur during the luteal phase?

Answer 8

-metestrus
-diestrus

Question 9

What are the characteristics of proestrus?

Answer 9

-begins when progesterone declines
-terminates at onset of estrus
-follicle development and rise in estradiol

Question 10

What are the characteristics of estrus?

Answer 10

-most recognizable stage
-peak of estradiol
-sexual receptivity and mating
-ovulation occurs

Question 11

What is standing estrus?

Answer 11

the female’s willingness to accept a male for mating

Question 12

What are the characteristics of metestrus?

Answer 12

-between ovulation and formation of functional corpora lutea
-initial development of CL
-transition from estradiol to progesterone

Question 13

What are the characteristics of diestrus?

Answer 13

-mature phase of CL
-progesterone dominance
-period of maximum luteal function
-longest stage of estrous cycle
-ends when CL is destroyed

Question 14

How does the estrous cycle compare to the menstrual cycle?

Answer 14

Estrous:
-interval between ovulations
-short follicular phase
-ovulation to begin cycle
Menstrual:
-interval between menses
-long follicular phase
-ovulation mid-cycle

Question 15

What occurs during the proliferative and secretory phases of the menstrual cycle?

Answer 15

changes in endometrial thickness

Question 16

What are the major events that occur during the follicular phase?

Answer 16

-elevated gonadotropins
-follicular growth
-preparation for ovulation
-sexual receptivity
-ovulation

Question 17

What are the characteristics of ovulation?

Answer 17

-after luteolysis and absence of progesterone
-dominant follicle secretes large amount of estrogens
-feedback to surge center leads to LH peak

Question 18

What happens after the surge center causes LH to peak?

Answer 18

-increase in PGE2 and blood flow
-increase in PGF2a
-increase in intrafollicular pressure
-disruption of connective tissue of follicle/weakening of follicle wall
-change from estradiol to progesterone
-removal of meiotic inhibition
-1st meiotic division

Question 19

What are the roles of granulosa and theca cells?

Answer 19

-luteinization
-switch from estrogen to progesterone

Question 20

What is the role of LH?

Answer 20

induction of ovulation

Question 21

What is the role of luteotropin?

Answer 21

essential for maintaining CL

Question 22

What are the characteristics of progesterone?

Answer 22

-prepares uterus for initiation/maintenance of pregnancy
-negative feedback with hypothalamus and pituitary
-stimulates endometrial secretion
-reduces myometrial motility
-poor progesterone synthesis/secretion can lead to repro. failure

Question 23

What are the characteristics of the corpus luteum lifespan?

Answer 23

-lifespan is preprogrammed
-luteolysis occurs if animal is not pregnant
-maternal recognition of pregnancy prolongs CL lifespan

Question 24

Which hormones control luteolysis?

Answer 24

-oxytocin
-progesterone
-PGF2a

Question 25

What is maternal recognition of pregnancy?

Answer 25

mechanism that prevents PGF2a secretion and produces a luteotropic hormone that stimulates/prolongs CL

Question 26

How does the uterus control the duration of the CL lifespan?

Answer 26

-PGF2a production -expression of oxytocin receptors

Question 27

What are the clinical uses of PGF2a?

Answer 27

-break CL and return animal to heat -estrous synchronization -short cycle -abortion

Question 28

How does progesterone prevent PGF2a secretion during the first half of the estrous cycle?

Answer 28

by blocking the formation of oxytocin receptors

Question 29

How do spontaneous ovulators differ from induced ovulators?

Answer 29

-spontaneous ovulators have endocrine triggers -induced ovulators have gonadotropin release in response to copulation

Question 30

Which animals exhibit polyestrus?

Answer 30

-cow -cat -pig -rodent

Question 31

Which animals exhibit seasonal polyestrus?

Answer 31

-horse -cat

Question 32

Which animals exhibit monoestrus?

Answer 32

dog

Question 33

What is polyestrus?

Answer 33

uniform distribution of cycles regularly throughout the year

Question 34

How do long day breeders differ from short day breeders in seasonal polyestrus?

Answer 34

-long day breeders are in heat in spring and summer -short day breeders are in heat in fall and winter

Question 35

What are the steps of the estrus cycle in the bitch?

Answer 35

-anestrus -proestrus -estrus -diestrus

Question 36

Why is there a delay between ovulation and fertilization in the bitch?

Answer 36

primary oocytes are ovulated and fertilization cannot occur for 48-72 hours after ovulation

Question 37

Why is there no luteolysis or maternal recognition of pregnancy in dogs?

Answer 37

the estrus cycle is long enough that this step does not need to occur

Question 38

How long does it take for ovulation to occur in dogs after the LH peak?

Answer 38

3 days

Question 39

What is postestrus?

Answer 39

an interestrus period in cats that follows estrus in which there was no mating, no ovulation, no CL development, and thus no diestrus

Question 40

What are the characteristics of anestrus?

Answer 40

-lack of cyclicity -lack of ovarian activity/no follicles or CLs -insufficient GnRH from hypothalamus to stimulate gonadotropin secretion

Question 41

What causes anestrus?

Answer 41

-age -pregnancy -lactation -nutrition -season -stress -pathology

Question 42

How can anestrus be diagnosed?

Answer 42

-ultrasound of ovaries -progesterone determination -previous records of GnRH or progesterone supplementation

Question 43

How does true anestrus differ from pseudoanestrus?

Answer 43

-in true anestrus, the ovaries are small and inactive -in pseudoanestrus, the ovaries are active, and there are other factors causing anestrus

Question 44

Which tests can be done to properly time insemination?

Answer 44

-vaginal cytology -endocrine levels

Question 45

How are progesterone levels used to determine breeding day?

Answer 45

-measure progesterone levels every 1-2 days once vaginal discharge begins -follow progesterone increase -breed two days post ovulation (typically two insemination times)

Question 46

What is galactorrhea?

Answer 46

spontaneous development of mammary glands with secretions

Question 47

What are the characteristics of pseudopregnancy in dogs?

Answer 47

-occurs at end of diestrus -associated with decline in progesterone -decrease in progesterone triggers increase in prolactin -prolactin causes clinical signs -typically resolves with no intervention -can occur following ovariohysterectomy