The Luteal Phase of the Estrous Cycle

Question 1

what is the dominant hormone in the luteal phase?

Answer 1

P4

Question 2

what part of the hormone cascade is ovvuring in a preovulatory follicle?

Answer 2

steroid synthesis of progesterone,which produces collagenase which acts on the theca interna

Question 3

when is the corpus hemorrhagicum present?

Answer 3

1-3 days following ovulation, during metestrus

Question 4

what is happening in the corpus hemorrhagicum? (4)

Answer 4

1. blood vessels in follicle wall rupture
2. walls collapse
3. cells intermix
4. old basement membrane becomes connective tissue of CL

Question 5

is the corpus luteum larger or smaller than the corpus hemorrhagicum in most species?

Answer 5

larger for most species

Question 6

what is the corpus luteum made of?

Answer 6

composed of cells from the granulosa and theca interna

Question 7

what us the hormonal result of the CL?

Answer 7

progesterone production increases

Question 8

does the small cavity present where the follicular antrum was have any effect on CL function?

Answer 8

no

Question 9

what does SLC stand for?

Answer 9

small luteal cell

Question 10

what does LLC stand for?

Answer 10

large luteal cell

Question 11

where does P4 production take place (an organelle)

Answer 11

in the mitochondria of the CL

Question 12

what do secretory granules of the CL contain and what is the function?

Answer 12

oxytocin: for cycling
relaxin: during pregnancy

Question 13

what 2 things contribute to the functional capability of the CL?

Answer 13

1. the number of luteal cells

2. vascularization of CL

Question 14

what happens to large luteal cells in the CL?

Answer 14

they undergo hypertrophy (gorwing in size)

Question 15

what happens to small luteal cells in the CL?

Answer 15

they undergo hyperplasia (increase in cell number)

Question 16

what initiates vascularization of the CL?

Answer 16

angiogenic factors from follicle

Question 17

what does CL vascularity effect?

Answer 17

CL steroid synthesis and delivery of hormones

Question 18

what is the result of insufficient CL function? why?

Answer 18

failure to maintain pregnancy; won’t have adequate P4

Question 19

list and describe the 2 targest of P4 stimulation

Answer 19

1. mammary gland: extra alveolar development

2. uterine endometrium: secretions for early embryo

Question 20

list and describe the 2 targets of P4 inhibition

Answer 20

1. myometrium: inhibit contractions

2. hypothalamus and anterior pituitary: negative feedback on surge AND tonic center, blocks estrus

Question 21

what 3 things are needed for luteolysis? describe their function if applicable
(2 hormones and an organ)

Answer 21

1. uterus: produces PGF2a in response to oxytocin
2. PGF2a
3. oxytocin: targets uterus

Question 22

describe the lifespan of a CL in a normal uterus and in a uterus with a contralateral hysterectomy (remove opposite side than ovulated on)

Answer 22

CL will have normal lifespan

Question 23

describe the lifespan of a CL after a total hysterectomy after CL production

Answer 23

longer CL lifespan, similar to gestation length, due to no uterus producing PGF2a to lyse CL

Question 24

describe the lifespan of a CL after an ipsilateral hysterectomy (removal of same side ovulated on) after CL production

Answer 24

CL lifespan shorter, less than 35 days

Question 25

describe the 3 steps of PGF2a control of luteolysis in cows, sows, and ewes

Answer 25

1. P4 causes production of oxytocin receptors in endometrium; oxytocin stimulates PGF2a release 2. prostaglandin synthesized by uterine endometrium and released into the uterine vein 3. PGF2a is picked up by ovarian artery through countercurrent exchange and delivered back to the ovary where it causes lysis of CL

Question 26

why does PGF2a circulate from the uterine horn on the side of ovulation directly into the uterine vein and artery of the CL?

Answer 26

is it metabolized very quickly in the lungs, so does not need to be in systemic circulation

Question 27

what happens to the formed CL in a mare after a hysterectomy?

Answer 27

the CL is maintianed

Question 28

what happens to formed CLs in a mare after either a contralateral or a ipsilateral hysterectomy?

Answer 28

50% of CLs maintained, doesn't matter which side removed

Question 29

describe the blood supply to the uterus and ovary in the mare compared to other species

Answer 29

completely different, much more widespread vasculature

Question 30

describe the metabolization of PGF2a in the mare and what that means for the CL?

Answer 30

mares don't metabolize PGF2a as efficiently as other species, so the CL is much more sensitive to PGF2a

Question 31

what is estromate?

Answer 31

a synthetic PGF2a used in cattle

Question 32

how much estromate is needed for CL regression in cattle?

Answer 32

5mL

Question 33

how much estromate is needed for CL regression in mares?

Answer 33

0.5 mL, MUCH LESS than cattle bc more sensitive

Question 34

on what days of the estrous cycle is PGF2a administration not effective for CL regression and only causes side effects for cows, ewes, and mares?

Answer 34

days 0-5

Question 35

how long are sows not responsive to PGF2a?

Answer 35

until day 12 of their estrous cycle

Question 36

when do sows produce their own PGF2a? what does this mean for administration of PGF2a?

Answer 36

day 15 of their estrous cycle; not really administered in sows

Question 37

list the 4 steps of luteolysis

Answer 37

1. P4 production by CL 2. towards end of diestrus (approx. d14) P4 causes endometrium to express oxytocin receptors 3. oxytocin from CL causes production of PGF2a in endometrium 4. PGF2a causes CL regression/lysis (cells die off)

Question 38

what 2 loops exist between oxytocin and PGF2a?

Answer 38

1, feedback loop | 2. auto-amplification loop

Question 39

describe the feedback loop between oxytocin and PGF2a

Answer 39

PGF2a from uterus or exogenous origin induces oxytocin production in the CL, which induces more PGF2a release from the endometrium (positive feedback)

Question 40

describe the auto-amplification loop of PGF2a in the CL and endometrium

Answer 40

PGF2a from endometrium or exogenous origin induces PGF2a production in the CL in a self-sustaining loop

Question 41

what 3 things need to happen in luteolysis?

Answer 41

1. decreased blood flow 2. cellular response 3. immune response

Question 42

describe the cellular response in luteolysis (2)

Answer 42

1. apoptosis: increase, organized die off | 2. Progesterone synthesis- decrease

Question 43

describe the purpose of the immune response in luteloysis and give the 2 cells that accomplish it

Answer 43

to clean up dead cells by phagocytosis; by lymphocytes and macrophages

Question 44

list the 2 differences between luteolysis in primates versus other animals

Answer 44

in primates: 1. does not require the uterus 2. CL lifespan in the human in 12-14 days unless pregnancy occurs

Question 45

what happens to the CL in the absence of pregnancy in primates?

Answer 45

CL self destructs via that auto-amplification loop

Question 46

what special thing does the human CL possibly contain and what is the purpose?

Answer 46

possible intra-ovarian oxytocin receptors and PGF2a production

Question 47

what stimulates the CL to stick around in humans?

Answer 47

hCG