Lecture 12: Parturition (Kelleman)

Question 1

Clicker Q: Which of the following are polyestrus and thus have repeated estrous cycles throughout the entire year? A’s: Queens, mares, bitches, cows, or wes

Answer 1

Ewes

Question 2

Clicker Q: Is progesterone high or low in diestrus?

Answer 2

high

Question 3

Clicker Q: Melatonin suppresses GnRH in which animal?

Answer 3

Mares

Question 4

Clicker Q: Luteinizing hormone (LH) causes:

Answer 4

ovulation

Question 5

Ferguson Reflex

Answer 5

Neuro-endocrine loop causing oxytocin release

Question 6

Main hormone for maintaining pregnancy

Answer 6

progesterone

Question 7

cervical closure fx. Maintained by which hormone?

Answer 7

Keeps contents from falling out and infection from getting in during preg. Progesterone

Question 8

Where is progesterone produced?

Answer 8

CL and placenta

Question 9

Which species have high progesterone throughout most of pregnancy?

Answer 9

ewe, sow, cow. Decreases in late-gestastion with estradiol peak

Question 10

rising estradiol –> progesterone

Answer 10

decreases

Question 11

HPA axis stands for

Answer 11

hypothalamic-pituitary-adrenal axis

Question 12

Activation of fetal HPA axis increases what 3 hormones

Answer 12

1) Corticotrpoin releasing hormone (CRH)
2) Adrenocorticotropin Hormone (ACTH)
3) Cortisol***

Question 13

Types of fetal stress

Answer 13

hypoxia, overcrowding, nutritional compromise

Question 14

Fetal HPA axis:

Name the 3 organs involved

Answer 14

hypothalamus –> anterior pituitary –> adrenal gland (cortex)

Question 15

Fetal HPA axis:

what hormone is released by the hypothalamus to stimulate the anterior pituitary?

Answer 15

CRF

Question 16

what hormone is released by the anterior pituitary to stimulate the adrenal gland?

Answer 16

ACTH

Question 17

Name the 3 functions of cortisol on the fetus:

Answer 17

1. induce enzymatic changes in the placenta ie “communicates” with mom
2. promotes prostaglandin synthesis
3. fetal maturation

Question 18

main action of progsterone

Answer 18

“pro-gestational”

“hormone of pregnancy”

Question 19

main function of estrogen

Answer 19

increased uterine “responsiveness”

Question 20

main function of PGF2-alpha

Answer 20

luteolysis and contractions

Question 21

main function of oxytocin

Answer 21

contractions

Question 22

main function of relaxin

Answer 22

genital tract softening

Question 23

Upon stimulation, what hormone can progesterone be converted to?

Answer 23

estradiol

Question 24

what hormone induces placental enzymes which convert progesterone to estradiol?

Answer 24

fetal cortisol

Question 25

what hormone is progesterone converted to before its final conversion to estradiol?

Answer 25

testosterone progesterone --> testosterone --> estradiol 21 carbons --> 19 carbons --> 18 carbons

Question 26

3 ways in which progesterone falls

Answer 26

1: enzymatic - fetal cortisol induces placental conversion of progesterone to estrogen 2: luteolysis - via PGF2-alpha and uterine contractions 3: removal of "progesterone block" (keeps fetus quiet during gestation)

Question 27

"progesterone block"

Answer 27

- keeps fetus quiet during gestation - during the removal of the "progesterone block" cortisol release induces progesterone to estrogen thereby decreasing progesterone and increasing estrogen.

Question 28

what way can estrogen can be increased (during parturition)

Answer 28

enzymatic - fetal cortisol induces placental conversion of progesterone to estrogen

Question 29

what are the three functions of estrogen?

Answer 29

1. increases uterine sensitivity to oxytocin 2. increases lubrication and sofening 3. promotes release of PGF2-alpha

Question 30

2 main functions of prostaglandin in parturition

Answer 30

1. causes luteolysis if CL is still present | 2. will cause uterine (myometrial) contractions

Question 31

what is the main function of oxytocin

Answer 31

myometrial contractions these contractions can subsequently promote more oxytocin and PGF2-alpha release.

Question 32

what is the main function of relaxin in parturition?

Answer 32

encourages pelvic, genital tract and cervical softening to facilitate parturition - this can be externally assessed as parturition nears: vulva, perineum and pelvic ligaments

Question 33

The Ferguson reflex

Answer 33

the sensation of distension of the cervix, uterus and vagina by the fetus results in a neuroendocrine reflex which causes the release of oxytocin (from posterior pituitary). oxytocin causes uterine contractions resulting in further distension, which increases oxytocin, causing further distension and contraction and so on.....

Question 34

Name the 3 stages of parturition

Answer 34

Stage I: "preparation" Stage II: fetal expulsion with "true labor" Stage III: expulsion of the fetal membranes

Question 35

what happens in stage I of parurition

Answer 35

- cervical dilation, myometrial contractions, some fetal positioning - behavior: nest building behaviors in dog & cat. cattle and sheep isolate themselves. mare shows colic-like signs (poor appetite and restlessness)

Question 36

what happens in stage II of parturition

Answer 36

start: rupture of the chorioallantois finish: complete expulsion of the fetus - myometrial and abdominal contractions. 1. chorioallantois breaks (1st fluid expulsion). 2. fetus is seen within the amnion. amnion breaks and amniotic fluid is released (2nd fluid expulsion).

Question 37

Stage III of parturition

Answer 37

expulsion of fetal membranes in species that are polytocus (more than one fetus), phase II and phase III often follow each other with each fetal passage. - mom experiences vasoconstriction and inflammation

Question 38

typical position of fetus upon actual parturition

Answer 38

anterior, dorsosacral, forelimbs extended.

Question 39

species variability in length of each stage of parturition | general - no specific numbers

Answer 39

cow - slow heifer - even slower horse - fast, "explosive"

Question 40

define: Lochia

Answer 40

the normal fluid which is passed from the uterus during the purerperium. it consists of cellular (RBC, WBC, bits of tissue, etc) and noncellular debris (fetal fluids, lysed blood, mucus, etc). - time varies by species minimal odor!

Question 41

type of contractions throughout parturition

Answer 41

uterine myometrial (smooth muscle) contractions abdominal contractions: - straining against closed glottis - additive with smooth muscle contractions

Question 42

time from fetal delivery until complete uterine involution is defined as:

Answer 42

Puerperium

Question 43

Complete Uterine Involution varies by species. cow? mare? bitch?

Answer 43

uterine involution = transformation from pregnant to non-pregnant state ``` mare = ~ 2 weeks cow = 1 - 1.5 months bitch = about 2 months or more ```

Question 44

Retained Fetal Membranes (RFM)

Answer 44

aka "retained placenta" - when placenta is not expelled in its entirety within a given time for each species. - incomplete expulsion - autolysis (rotting) - minor to serious health problems may result depending upon species - involution is delayed by RFM

Question 45

dystocia

Answer 45

"difficult birth"

Question 46

Equine RFM is how much time after fetal delivery?

Answer 46

3 hours - considered a true emergency - potentially life threatening

Question 47

Bovine RFM - how much time after fetal delivery?

Answer 47

> 12 hours

Question 48

General parturition summary

Answer 48

1. Fetal HPA activation 2. decreased Progesterone 3. increased estrogen 4. increased oxytocin and PGF2-alpha relative uterine quiescence changes to dramatic uterine activation!