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Animal Production > Establishment of pregnancy > Flashcards

Establishment of pregnancy Flashcards

1
Q

Pregnancy

A

The period between fertilization and birth involving
-internal fertilization
-retention of fertilized egg, embryo, fetus within femal repro tract
-direct maternal nourishment (matrotrophy)

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2
Q

What drives pregnancy?

A

Driven by development of live birth (viviparity) on to mammalian biology

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3
Q

Advantages to pregnancy

A

-protection from thermal extremes, osmotic stress, and predation

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4
Q

Disadvantages to pregnancy

A

-increased maternal energy use
-reduced maternal mobility and fecundity
-risk of injury to both mother and fetus from immunological and inflammatory responses in utero

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5
Q

Fecundity

A

Reproductive output of an individual over time

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6
Q

Types of implantation in uterus

A
  1. Group where pre-attachment period within uterus is long (most domestic animals)
  2. Group of animals where the blastocyst implants quickly after entering the uterus (primates)
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7
Q

Long pre-attachment period implantation

A

-Maternal recognition of pregnancy signal is produced and the maternal recognition of signal must occur before the attachment period to the uterus

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8
Q

Long pre-attachment period membrane development

A

extensive extra-embryonic membrane development occurs as a result of body folding to produce amnion,allantois, chorion

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9
Q

Quick blastocyst implantation method

A

-membrane development occurs after implantation
-maternal recognition signal rapidly increased after implantation

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10
Q

Implantation of dog

A

-Canine zygotes take a fairly long time to reach the uterine tubes compared to other species (7-10 days)

-Intrauterine migration occurs from day 12-17 so blastocysts can become evenly spaced throughout each horn

-Fixation and implantation starts at day 17

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11
Q

Implantation in Cat

A

-limited info; blastocysts appear to reach uterus by day 6, become slightly ellipsoid and then hatch from zona by day 11
-intrauterine migration and implantation starts by day 12

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12
Q

Elongation in ruminants and pig

A

-Blastocyst expansion continues becoming tubular and then filamentous

**sphere of 10-15mm, filamentous 1mm X 100-200mm at day 10, dilamentous structure is 1m long by day 12-15

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13
Q

Elongation purpose

A

-Provides max surface area of contact between trophectoderm/trophoblast and maternal uterine epithelium

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14
Q

Elongation in bovine

A

-elongated embryo can extend into the non-pregnant uterine horn

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15
Q

Embryo elongation in horses, carnivores, primates

A

**does not elongate! Remains spherical

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16
Q

Histotrophe

A

The secretory products of the endometrial glands

Includes: enzymes, growth factors, cytokines, hormones transported to lumen, transport proteins , nutrients

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17
Q

Purpose of histotrophe

A

-nourishes the embryo during the pre-implantation period and in some species during the post-implantation period.
**promotes survival, development, production of pregnancy recognition factors, implantation, placentation

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18
Q

How do the endometrial glands develop for max production of histotrophe?

A

Undergo hyperplasia and hypertrophy to increase SA

**less in humans but occurs in sheep, cows, goat, pig, horse

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19
Q

Luteolysis

A

breakdown of corpus luteum. Must be avoided to continue pregnancy

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20
Q

Dogs and cats maternal recognition of pregnancy

A

These species do not have an MRP signal because luteal phase is long and close to the gestation phase regardless whether there is a pregnancy of not

21
Q

Maternal recognition of pregnancy (MRP)

A

-needed in species that aren’t dog or cat BECAUSE length of luteal phase ends before embryo normally implants. Conceptus will send MRP to prolong CL

22
Q

Types of recognition signalling from conceptus

A
  1. Luteotrophic

2.Anti-luteolytic

23
Q

Luteotrophic

A

A hormone to act on the CL to maintain luteal function

24
Q

Anti-luteolytic

A

A hormone to prevent uterine release of luteolytic-promoting substances such as prostaglandin F2-alpha

25
Q

CL production of progesterone results in:

A
  1. Support secretory function of endometrium, embryonic development, implantation, placentation
  2. Be a negative feedback on hypothalamus and anterior pituitary to inhibit follicular development and ovulation
  3. Prevention of return to estrus in polyestrous species (large and small ruminants, horse, pig)
26
Q

Signal for recognition of cow, ewe, goat

A

Interferon tau

27
Q

Signal for recognition of Sow

A

Estradiol (two embryos per horn)

28
Q

Signal for recognition for mares

A

proteins and embryo migration

29
Q

Maternal recognition signal and attachment

A

Attachment will always occur after the mother has recognized the pregnancy.
**need MRP!!!

30
Q

IFN tau in cow, ewe, goat

A
  1. IFN tau acts on endometrial cells of uterus and inhibits oxytocin receptor production. Therefore oxytocin cannot bind to receptors that stimulate PGF2alpha production
  2. IFN tau increases secretion of proteins from endometrial glands which enter lumen and nourish the embryo
31
Q

Paracrine mechanisms affecting endometrium

A
  1. ovary produces estrogen
  2. Estrogen binds to estrogen receptors of uterus
  3. increases oxytocin receptors in uterus
  4. Oxytocin from ovary and pituitary binds to oxytocin receptors and produce PGF2alpha =luteolysis
32
Q

How does IFN-tau effect endometrium paracrine mechanisms differently in ewe/goat vs. cows?

A

IFN-receptor in ewe/goats blocks the estrogen receptors in uterine nucleus

VS.

IFN-receptor in cows block oxytocin receptors in uterine epithelium wall

33
Q

IFN-tau impact on endocrine mechanism

A

-IFN-tau can be transported from utero-ovarian vein to ovarian artery and then to CL
>results in sustained CL function and production of progesterone AND prevents lytic events of any PGF2alpha on CL

34
Q

IFN-tau impact on conceptus elongation

A

IFN-tau stimulates production of small cytokines secreted by endometrium to induce growth, induces expression of genes responsible in endometrium for uterine attachment, AND stimulates endometrial gland development and function (nutrients!)

35
Q

Normal mechanism in non-pregnant sow

A

-Oxytocin from endometrium, posterior pituitary, and CL promote PGF2alpha production in endometrium which can reach ovary and initiate luteolysis

36
Q

Estradiol induced mechanism in pregnant sow

A

Estrogen (secreted between days 11-15) is the main pregnancy recognition signal from the conceptus.
Estradiol re routes PGF2alpha to uterine lumen where it is destroyed preventing luteolysis

37
Q

Roles of estradiol in sows

A

-prevent luteolysis
-induces expression of genes (osteopontin) in uterus responsible for conceptus attachment (day 15-25)
-stimulate production of endometrial prolactin receptors
-promote uterine gland development and increased ion and nutrient transport for conceptus
-promote tolerance (immunity) of progesterone primed endometrium to implantation/attachment

38
Q

Estradiol and PGE2

A

Estradiol from the conceptus stimulates uterine epithelia to secrete Prostaglandin E2, and then the conceptus starts secreting it

Then PGE2 will reach CL from utero-ovarian vein to the ovarian artery= Luteoprotective role in CL

39
Q

MRP signal in equine

A

Unknown. However removal of equine conceptus at various points of pregnancy lengthens the time required for return to estrus

40
Q

Equine conceptus role

A

-produces estradiol and estrone in large amounts, which enhances uteroferrin but does not extend CL lifespan.
-uterine PGF2alpha secretion appears blocked but not sent to lumen, so due to decrease in PTGS2 (COX-2) activity
-no IFN secretion occurs

41
Q

Trans-uterine migration of equine conceptus

A

CRITICAL embryo migration

  • during pre-attachment phase, horse conceptus is moved over endometrial surface by contractions (12-14/day)
    -due to pregnancy recognition factors by conceptus, the production of PGF2alpha is reduced and there is decreased PTGS2 activity
42
Q

Attachment or implantation

A

-movement and transient attachment, firm adhesion of trophectoderm to uterine lumenal and superficial glandular epithelia

43
Q

Phases of attachment

A
  1. Shedding of Zona pellucida
  2. Pre contact period- when blastocysts can migrate and undergo orientation without contact with epithelia. Initiate pregnancy recognition signalling
  3. Trophectoderm associates with endometrial epithelium for unstable adhesion. (Also in ruminants, development of microvilli starts)
    4.Trophectoderm firmly adheres to luminal epithelium and in some species superficial glandular epithelium
    5.Unique to species with invasive implantation of blastocyst through uterine luminal epithelium into uterin stroma that becomes decidualized
44
Q

Uterine receptivity

A

the interactions between the developmentally competent conceptus and uterine endometrium (pre-contact, apposition, firm adhesion, invasion)

45
Q

What drives uterine receptivity?

A

-progesterone, estrogens

-Also IFN-tau in ruminants

46
Q

Steps of uterine receptivity

A
  1. Loss of anti-adhesive cell surface glycoproteins called mucins from luminal epithelial cells of endometrium
  2. Unmasks surface adhesion molecules on endometrium
    >Selectins- low affinity contacts; for initial attachment of conceptus
    >integrins and ECM- high affinity contacts; stable adhesion of conceptus

Conceptus has receptors and ECM secretion of its own for binding to endometrium

47
Q

Pregnancy Loss and reproductive performance

A

A high rate of pregnancy loss reduces reproductive performance.

48
Q

What periods are responsible for majority of pregnancy losses?

A
  1. From fertilization to blastocyst development (10-50%)
  2. MRP, conceptus elongation, uterine receptivity (20%)

Animal Production (17 decks)

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