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ANSC 312 - Repro Physiology > Midterm 3 - Lecture 23 > Flashcards

Midterm 3 - Lecture 23 Flashcards

1
Q

4 steps in pre-attachment embryonic development

A
  1. development within the Zona Pellucida
  2. hatching from the Zona Pellucida
  3. maternal recognition of pregnancy
  4. extra-embryonic membranes
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2
Q

Ootid

A

oocyte after the 1st meiotic division in which the 1st polar body is present

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3
Q

What is syngamy? Where does it occur? What does it give rise to?

A

fusion of the male and female pronuclei within the cytoplasm of a newly fertilized oocyte, giving rise to a zygote

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4
Q

Zygote

A

diploid cell resulting from the fusion of the male and female pronuclei

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5
Q

Embryo

A

animal in the early stages of development that has not taken on an anatomical form that is recognizable as a member of a species

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6
Q

Fetus

A

unborn young that possesses identifiable features of a given species

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7
Q

Conceptus

A
  • a product of conception including:
    1. embryo in early development (preimplantation)
    2. fetus and placenta (postimplantation)
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8
Q

What occurs during fertilization to produce a zygote?

A

during fertilization syngamy occurs to produce a zygote that begins to go cleave (mitotic division) to give rise to blastomeres

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9
Q

What is cleavage?

A

Cleavage of blastomeres (2, 4, and 8-celled embryo) to form ball of cells within the zona pellucida referred to as a Morula

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10
Q

What is blastcoele development?

A
  • two groups of cells form in the Morula - process of compaction
    1. outer cells - adhesions create tight jxns btw cells
    2. inner cells - connected by gap jxns btw cells
  • sodium is pumped into the intercellular spaces and water follows osmotically = fluid accumulation within the morula
  • fluid accumulation causes outer cells to flatten and blastocoele forms
  • two separate cellular components emerge
    1. inner cell mass (ICM)
    2. trophoblast
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11
Q

What is the process of compaction during blastcoele development?

A

two groups of cells form in the Morula - process of compaction
1. outer cells - adhesions create tight jxns btw cells
2. inner cells - connected by gap jxns btw cells

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12
Q

What 2 cellular components emerge during blastocoele development?

A
  1. inner cell mass
  2. trophoblast
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13
Q

What happens during blastocyst hatching?

A
  • blastocyst eventually “hatches” from the Zona Pellucida
  • Hatching caused by 3 factors
    1. growth and accumulation of liquid within the blastocyst
    2. enzymes from the trophoblast that degrade the ZP
    3. contractions of the blastocysts
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14
Q

Do blastocysts form at the same time in all species?

A

No! There is variation

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15
Q

When doing embryo transfer, what is collected and transferred?

A

blastocysts
- if they have hatched it is too late

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16
Q

What does successful pregnancy maintenance require?

A
  • high blood P4 concentrations
  • PGF2a induced luteolysis must be prevented
  • conceptus can play an active role in maintaining pregnancy
17
Q

How do cows and ewes recognize pregnancy?

A
  • blastocyst(s) produce interferon to prevent luteolysis; inhibits the oxytocin-receptor development so that oxytocin cannot stimulate PGF2a production by the uterine endometrium
18
Q

How do sows recognize pregnancy?

A
  • blastocysts produce estradiol to prevent luteolysis; cause PGF2a production by the uterine endometrium to be rerouted into the uterine lumen where it is destroyed
  • # of conceptus is important
19
Q

How do mares recognize pregnancy?

A
  • proteins/estradiol synthesis and contact of the conceptus with endometrium prevents luteolysis
20
Q

How do bitches and queens recognize pregnancy?

A
  • does not require a signal from the conceptus; lifespan of the CL is longer than the gestation period
21
Q

What 3 factors does luteolysis depend on?

A
  1. presence of oxytocin receptors on uterine endometrium
  2. oxytocin production by the large luteal cells
  3. PGF2a synthesis by uterine endometrium
22
Q

What are the hormones of pregnancy?

A
  • Early pregnancy factor
  • Progesterone
  • Equine Chorionic Gonadotropin
23
Q

What are the hormones of parturition?

A
  • Adrenal Corticotropin (ACTH)
  • Estrogens
  • Prostaglandin F2a
  • Relaxin
  • Oxytocin
24
Q

Early Pregnancy Factor (EPF)

A
  • a protein (chaperonin 10) expressed into the maternal circulation prior to embryonic attachment (human, cattle, sheep, pigs)
  • shown to have immunosuppressive properties
  • Early Pregnancy Test based on EPF
25
Q

What is the dominant hormone of pregnancy?

A

Progesterone

26
Q

Progesterone

A
  • dominant hormone of pregnancy
  • essential for embryonic/fetal development to prevent return to estrus and produce uterine environment appropriate for implantation
  • provides the Progesterone Block that inhibits myometrial contractions during pregancny
27
Q

Progesterone production

A
  • P4 produced by CL in early pregnancy
  • Placenta can eventually takeover P4 production
  • Role of CL and Placenta in P4 production varies among species
28
Q

How does the role of CL and Placenta in P4 production vary among species?

A

Ewe & Mare
- placenta takes over P4 in early gestation

Cow
- placenta takes over P4 in late gestation

Sow, Bitch & Queen
- Cl is the source of P4 through out gestation

*when the placenta takes over the major P4 production role, the CL continues to produce P4

29
Q

Gestation Lengths: ewe, mare, cow, sow, bitch, queen

A

Ewe = 5 months
Mare = 11 months
Cow = 9 months
Sow = 3.8 months
Bitch = 2 months
Queen = 2 months

30
Q

What is eCG produced by? When does eCG secretion peak? When do eCG secretions bottom out?

A
  • eCG is a gonadotropin produced by the endometrial cups of the placenta
  • endometrial cups begin to form and express eCG at the time of attahcment
  • cup development and eCG secretion peaks midway through the 1st trimester
  • cups regress and eCG secretion bottoms-out by ~Day 100 of Gestation
31
Q

Where is eCG produced?

A

endometrial cups of the placenta

32
Q

Role of eCG

A
  • maintains CL production of P4 during the 1st trimester by maintaining the Primary CL
  • as eCG increases the mare will ovulate to create an accessory CL which will takeover P4 production
  • placenta assumes the major P4 producing role by ~day100
33
Q

What effect does eCG have on other species?

A

strong FSH-like effect on other species and is often used as a part of superovulation protocols

34
Q

CL P4 output of the mare in early gestation

A
  1. P4 from primary CL increases and then decreases
  2. eCG re-stimulates P4 production by primary Cl
  3. eCG continues to increase, accessory Cl forms and P4 increases

*after day 100 placenta assumes major P4 production

35
Q

What does the uterine endometrium produce?

A
  • various growth factors and cytokines that stimulate growth and development of the fetus in utero

ANSC 312 - Repro Physiology (21 decks)

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