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Theriogenology > Parturition > Flashcards

Parturition Flashcards

1
Q

3 pre-partum steps?

A

-Formation of placenta
-Acquisition of the endocrine function of the placenta
-Initiation of parturition

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2
Q

What are the two components of placenta classification?

A

-Distribution of chorionic villi
-# of tissue layers separating maternal and fetal blood

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3
Q

What is the chorion?

A

The chorion is the fetal contribution to the placenta.

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4
Q

What is the functional unit of the placenta?

A

The functional unit of the placenta is the chorionic villus.

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5
Q

What are chorionic villi?

A

Chorionic villi are finger-like projections on the surface of the chorion that protrude towards the endometrium.

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6
Q

What are the extraembryonic membranes? (3)

A

Amnion, allantois, chorion

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7
Q

Types of placentas by distribution of chorionic villi

A

Diffuse, zonary, discoid, cotyledonary

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8
Q

What defines a diffuse placenta?

A

Uniform distribution of villi throughout the chorion

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9
Q

What species has a diffuse placenta?

A

Mare

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10
Q

Endometrial cups in mares; origin, what do they produce and when do they develop?

A
  • Transitory structures à
    endometrial cups (mm to
    cm)
  • Trophoblastic and
    endometrial origin
  • Produce eCG
  • Develop between 35 and
    60 days of pregnancy
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11
Q

What defines a zonary placenta? what are the zones

A

Band like zone of chorionic villi. Consists of 3 zones; transfer zone, pigmented zone, and relatively non vascular zone called the allantochorion

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12
Q

What species have a zonary placenta?

A

Cats and dogs

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13
Q

What defines a discoid placenta?

A

Forms a regionalized disc. Consists of a round patch of chorionic tissue that forms the fetal-maternal interface

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14
Q

What species have a discoid placenta?

A

Primates and rodents

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15
Q

What defines a cotyledonary placenta?

A

Numerous, discrete button like structures called cotyledons

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16
Q

What species has a cotyledonary placenta?

A

Ruminants

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17
Q

Types of placentas named based off of number of tissue layers separating maternal and fetal blood

A
  • Epitheliochorial
  • Endotheliochorial
  • Hemochorial
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18
Q

What species have an epitheliochorial placenta

A

sow and mare

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19
Q

What species have an endotheliochorial placenta

A

dogs and cats

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20
Q

What species have an hemochorial placenta

A

primates and rodenst

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21
Q

What is special about the ruminant placenta in relation to the # of layers?

A

Ruminants have epitheliochorial placenta, with endometrial epithelium that
erodes and regrows –> syndesmochorial (maternal capillaries transiently exposed to chorionic epithelium)

22
Q

What 4 hormones does the placenta produce?

A

P4, E2, relaxin, placental lactogen

23
Q

What species is relaxin not produced in

A

Cows

24
Q

What hormone is not sufficiently produced in the cow placenta?

A

P4

25
Q

Why is progesterone essential for early embryonic development?

A

Progesterone is obligatory for early embryonic development.

26
Q

What role does high progesterone play during pregnancy?

A

It maintains the “progesterone block,” inhibiting strong myometrial contractions throughout pregnancy

27
Q

How does the role of the corpus luteum (CL) in maintaining pregnancy vary among species?

A

In some species, like the ewe, mare, and women, the CL is not needed for the entire gestation as the placenta takes over progesterone production.

28
Q

What happens in the sow and rabbit if the CL is removed?

A

Removal of the CL results in termination of pregnancy regardless of the stage of gestation.

29
Q

What effect does CL removal have in cows during gestation?

A

Removal of the CL up to 8 months of gestation results in abortion

30
Q

What cascade occurs after the estrodiol is present

A

estradiol -> myometrial contractions -> pressure -> cervical stimulation -> oxytocin -> maximum pressure

31
Q

What is another result of estradiol in the cascade?

A

Leads to secretion by placenta -> lubrication

32
Q

What hormone does fetal cortisol produce

A

PGF2alpha ; which induces luteolysis

33
Q

What does PGF2alpha lead to further excretion of?

A

PGE2 and relaxion … which leads to cervical dilation and pelvic ligament stretching

34
Q

What does fetal cortisol activate to get progesterone converted to estradiol?

A

-Fetal cortisol activates
17a-hydroxylase,
17-20 desmolase, and aromatase that convert progesterone to estradiol

-This conversion removes the
“progesterone block”

35
Q

What occurs during the fergusson reflex?

A
  • Pressure is created on the
    cervix as fetus moves into
    the birth canal
  • This stimulates the afferent
    sensory neurons and PVN
    (paraventricular nucleus)
  • Oxytocin is secreted from
    posterior pituitary lobe
  • Oxytocin stimulates
    myometrial contractions
36
Q

What happens in the lung as a result of fetal cortisol?

A

increased surfactant production by type 2 pneumocytes

37
Q

What happens in the blood as a result of fetal cortisol?

A

conversion of fetal to adult hemoglobin

38
Q

What happens in the liver as a result of fetal cortisol?

A

increased glycogen deposition

39
Q

What happens in the pancreas as a result of fetal cortisol?

A

increased pancreatic islet cell response to glucose

40
Q

What happens in the thyroid as a result of fetal cortisol?

A

increased activated of T3 generating enzymes

41
Q

Placental cortisol actions (overall, increase, decrease)

A

Terminates progesterone block and initiates estrogen production leading to the onset of lactation

DECREASE
1. The presence or activity of the placental factors
2. Progesterone synthesis and secretion

INCREASE
1. Placental estrogen synthesis and secretion
2. Prostaglandin synthesis and secretion from
placenta and endometrium

42
Q

What 5 events occur just before parturition?

A
  1. Softening of the pelvic ligaments
  2. Cervix softens and begins secreting mucus
  3. swelling of the vulva
  4. Udder swells- edema, fills with first milk
  5. Fetus moves into proper position
43
Q

What causes softening of the pelvic ligaments

A

Due mainly to estrogens and relaxin; collagenase breaks down collagen which also “stretches” the pelvis

44
Q

What leads to the cervix softens and begins secreting mucus

A

Increase water content in cervical tissue resulting in cervical plug release and lubrication of the birth canal

45
Q

What leads to swelling of the vulva

A

Hyperaemia caused by estrogen

46
Q

what causes udder swelling-edema, fills with first milk

A

Effect of prolactin, estrogens and glucocorticoids

47
Q

What occurs for the fetus to move into proper position

A

Resting on thorax, front feet and head facing the cervix

48
Q

Details of stage 1; dilation of cervix

A
  • Variable in length
  • Variable in clinical signs
  • Increased myometrial activity/fetal movement
  • Entry of fetus into cervical canal-reflex release of oxytocin
  • Ends with the rupture of the chorioallantois-“breaking
    water” (first water bag)
49
Q

stage 2; expulsion of the fetus/active labour

A
  • Pelvic location of fetus-further release of oxytocin
  • Peak oxytocin levels occur during this stage
  • Forceful uterine and abdominal contractions
  • Amnion ruptures-lubricates vestibular vagina (second water bag)
  • Ends with delivery of the fetus or fetuses
50
Q

stage 3; expulsion of fetal membranes/afterbirth

A
  • Variable in duration
  • Continued uterine contractions
  • Passage of the placenta
  • In polytocous species, placentas are usually passed during labour or shortly after birth of the last offspring

Theriogenology (12 decks)

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