Luteal Cycle

Question 1

at what stage does the preovulatory LH surge occur?

Answer 1

estrus

Question 2

define ovulation

Answer 2

ovulation is a series of events that ends with

1. the follicle expelling the mature cumulus-oocyte complex (among other contents)
2. the begining of CL develoopment

Question 3

The preovulatory LH surge directly causes 5 things…

Answer 3

1. increase in PGE2
2. increase in PGF2
3. shift from E2 to P4 by dominant follicle
4. breakdown between granulosal cells and oocyte
5. changes on the surface epithelium

Question 4

ovulation is mechanically caused by

Answer 4

1. an increase in folliular pressure
2. weakening of follicle walls

Question 5

in spontaneous ovulators

Answer 5

ovulation occurs at regular intervals depending upon the circuation of estradiol

(ex. human, sheep, cattle, horses, pigs, most rodents)

Question 6

in induced ovulators

Answer 6

ovulation is associated with sex
(ex. rabbits, ferrets, cats, camelids)

Question 7

pathway of induced ovulation

Answer 7

1. stimulation of sensory nerves in vagina and cervix
2. impulses relayed through spinal cord to surge center

Question 8

site of ovulation

Answer 8

in mares, the ovulation fossa
in other female animals, anywhre on the surface of the ovary

Question 9

time peroid of luteal phase

Answer 9

ovulation to luteolysis (mestrus and diestrus in between)

Question 10

3 Major Process of Luteal Phase

Answer 10

1. luteinization (transformation of follicular cells into luteal cells after ovultion)
2. synthesis and secretion (growth and development of CL due to increasing progesterone)
3. luteolysis (regression of CL)

Question 11

what occurs during the luteinization phase?

After ovulation…

Answer 11

the follicular (theca interna and granulosa) cells are transformed into the corpus luteum (luteal cells)

Question 12

what occurs during luteolysis?

Answer 12

• regression/damage of Corpus Luteum
• dramatic drop in blood progesterone

Question 13

Corpus Hemorrhagicum is defined as

Answer 13

the process in which the corpus luteum forms

Question 14

How does Luteinization mechanically occur?

Answer 14

ovulation causes the follicular structure to collaspe which mixes theca and granulosa cells and transforms them into luteal cells

Question 15

large luteal cells (LLC)

Answer 15

• originate from granulosa cells
• secrete progesterone and oxytocin

Question 16

small luteal cells (SLC)

Answer 16

orginate from the theca interna cells and secrete progesterone

Question 17

the types of CL differ in

Answer 17

their lifespan and steroidogenic output

Question 18

name the types of CL’s

Answer 18

1. cycle (CL spurium)
2. pseudopregnancy
3. pregnancy (CL verum)
4. lactation

Question 19

the CL of pregnancy is

Answer 19

only found in mammalian species

Question 20

the CL of the cycle

Answer 20

doesn’t exist in induced ovulatiors

Question 21

the CL of pseudopregnacy

Answer 21

doesn’t form in primates

Question 22

the CL of lactation

Answer 22

only occurs in induced ovulators

Question 23

in rodents

Answer 23

all four types of CL can be found

Question 24

LH stimulates…

Answer 24

Progesterone synthesis

Question 25

progesterone is derived from

Answer 25

chlolesterol

Question 26

genomic or slow progesterone response

Answer 26

causes uterine gland secretion

Question 27

Non-genomic or fast progesterone response causes

Answer 27

ion channel inhibition to reduce myometrial contractions

Question 28

Functions of Progesterone

Answer 28

1. prepares endometrium for implantation
2. maitence of pregnancy by inhibiting myometrium motility
3. (along with estrogens) induces behavioral estrus
4. inhibits estrus and the ovulatory surge of LH at high levels
5. develops secretory tissue (alveoli) of the mammary glands

Question 29

Luteolysis is triggered by ___ hormone

Answer 29

PGF2delta which is secreted by the uterine endomtrium in farm animals (ovary in primates)

Question 30

effect of urerextomy on ewe

Answer 30

• with a total uterectomy, the CL lifespan is similar to a normal gestation length
• a partial uterectomy contralateral to the CL will lead to a lifespand similar to a normal cycle
• a partial uterectomy ipsilateral to the CL will cause the CL to have a lifespan longer than normal

Question 31

transport of PGF2a im cow, ewe, and sow

Answer 31

• it is secreted by the uterus and transported directly to the ovary, which avoids diluting PGF2a in systemic circulation
• PGF2a is then metabolized in the lungs and quickly eliminated through breathing

Question 32

in mares, PGF2a

Answer 32

IS released into systemic circulation, meaning that it isn’t metabolized as quickly and the CL is more sensitive to it (in comparison to ewes, cows, etc)

Question 33

PGF2a is derived from

Answer 33

pnospholipids, meaning it binds to receptors on the outer mitochondrial membrane

Question 34

change in PGF-M during late diestrus and proestrus

Answer 34

increases

Question 35

During the Early Luteal Phase

Answer 35

• progesterone blocks oxytocin receptors in the endometrium which prevents the secretion of PGF2a
• causes continous secretion of progesterone by CL

Question 36

During the late luteal phase

Answer 36

• progesterone loses its ability to block oxytocin receptors
• therefore oxytocin initiates the synthesis of PGF2a in the endometrium
• PGF2a acts on CL to release luteal oxytocin which causes endometrial oxytocin receptors to amplify the relese of PGF2a from the endometrium
• closed loop system is formed, both oxytocin and PGF2a are produced to inhibit progesterone secretion until the completion of luteolysis

Question 37

The Loss of Progesterone Secretion from Luteal Cells Occurs Because…

Answer 37

1. PGF2a binds to receptors on membrane of luteal cells
2. influx of Ca+ occurs which causes an apoptotic effect
3. Activation of PKC that ultimetly inhibits progesterone synthesis

Question 38

luteoysis and cyclicity

Answer 38

luteolysis is the driving force for continued cyclicity

Question 39

hormone that destroys the CL

Answer 39

PGF2a