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ANIMAL PRODUCTION - Reproduction > 10 – Fertilization and Pre-Implantation Development > Flashcards

10 – Fertilization and Pre-Implantation Development Flashcards

1
Q

Mating

A
  • Union of male and female gametes
  • Occurs at PEAK of female fertility (in most vertebrates)
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2
Q

Capacitation

A
  • Process of physiological alterations of sperm so they are COMPENENT to fertilize the oocyte
  • Requires the female reproductive tract
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3
Q

Sperm undergo (capacitation)

A
  • Removal of membrane cholesterol to improve oocyte binding
  • Increase intracellular Ca2+ concentration
  • Increase in intracellular pH
  • Protein phosphorylation
  • Hyperactivated motility (ex. asymmetrical beating)
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4
Q

Functional affects (capacitation)

A
  • Penetrate cumulus cell matrix
  • Adherence to zona pellucida of oocyte
  • Undergo zona-stimulated acrosome reaction
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5
Q

Uterus and Uterotubal Junction (UTJ)

A
  • Sperm maintained at HIGH numbers at UTJ after ejaculation
  • Beyond cervix, UTJ is second major barrier with lots of FOLDS
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6
Q

Isthmus as a reservoir

A
  • Sperm bind ciliated oviduct epithelial cells (OECs) that have SPECIFIC GLYCOPROTEINS
  • Can be bound for 2-4 days=HIGH quality
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7
Q

Pre-ovulatory period

A
  • E2 elevated in circulation and oviductal fluid
  • *promote SHORT TERM SPERM STORAGE
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8
Q

Post-ovulation

A
  • P4 rise in circulation and oviductal fluid
  • *chemotactic signal for sperm to MOVE TO AMPULLA and undergo CAPACITATION in ampulla
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9
Q

Fertilization ‘steps’

A
  • Sperm contact and penetration (through cumulus cell layer)
  • Zona pellucida (ZP) binding and acrosome reaction
  • Zona penetration
  • Sperm fusion with oocyte membrane and ooplasm
  • Cortical granule release from oocyte
  • Pronuclear fusion and initiation of metabolism
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10
Q

Sperm plasma membrane covering acrosome: 2 receptor regions

A
  • Zona binding region (ZBR)
  • Acrosome reaction promoting region (ABPR)
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11
Q

Zona binding region (ZBR)

A
  • Binds zona pellucida-3 glycoproteins on oocyte zona (ZP3)
    o Attaches sperm to zona
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12
Q

Acrosome reaction promoting region (ABPR)

A
  • Binds ZP3 and starts acrosome reaction (ex. fusion of membranes)
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13
Q

Acrosome reaction

A
  • Overlying plasma membrane FUSES with OUTER ACROSOMAL membrane
  • *contents released (eg. ACROSIN) and digest zona proteins and increase sperm biding to zona
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14
Q

What is left after acrosomal reaction?

A
  • Inner acrosomal membrane and equatorial portion of sperm head
  • *increase binding to oocyte membrane
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15
Q

Post-acrosome reaction

A
  • Sperm penetrates zona and into perivitelline space
  • Oocyte produced CORITCAL GRANULES accumulate at periphery
  • Oocyte and sperm fuse at equatorial region
  • Granules RELEASE CONTENTS
  • Sperm nuclear contents decondense
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16
Q

Cortical granules release contents (2 mechanism to prevent polyspermy)

A
  1. Change zona to PREVENT polyspermy (zona block/reaction)
    AND/OR
  2. Change oocyte membrane to PREVENT sperm attachment (vitelline block)
    Ex. mucopolysacchardies, proteases, plasminogen activator, phosphatases
17
Q

Pronuclei

A
  • Fuse=diploid
  • DNA replication
  • Male mitochondria including mtDNA are DEGRADED
  • *only maternal mitochondria remain
18
Q

Cleavage division during preimplantation development deviations from normal cell division

A
  • rapid multi-cellularity
  • no growth
  • shape is maintained
  • asynchronous in mammals (can appear as 3-5 cell under microscope)
19
Q

Holoblastic (cleavage division)

A
  • Division completely cuts through the embryo
  • Occurs in embryos with moderate (ex. amphibians) to LITTLE/NO YOLK (ex. mammals)
  • Equal or unequal
  • *ROTATIONAL in mammals
20
Q

Rotational holoblastic division in mammals

A
  • Cleavage produces blastomeres at RIGHT ANGLES to one another
21
Q

Pre-implantation/pre-attachment development in mammals

A
  • Period of embryonic development from FERTILZATION to JUST PRIOR TO IMPLANTAION or uterine attachment
  • Timing/stage varies among species
22
Q

Activation of embryonic genome

A
  • During oocyte development lots of maternal mRNA has been stored and proteins made=*important for oocyte to survive
  • MUST OCCUR to survive!
  • Varies in species
23
Q

Morphogenic events

A
  • Compaction
  • Cavitation
  • Blastocyst expansion
24
Q

Morphogenetic event I: compaction

A
  • After 3rd cleavage
  • Outside cells: Individual blastomeres start to tightly attach to one another (NO fusion, future trophectoderm ->trophoblast=extraembryonic lineage)
  • Cells on inside: connected by gap junctions
    o Derive the embryo by forming ICM
  • MORULA (16-cell stage)
  • *2 regions synthesize different proteins
25
Q

Morphogenetic event II: cavitation

A
  • Fluid accumulates in compacted morulae forming SMALL vesicles
  • Vesicles coalesce into blastocoel=blastocyst
  • *Na,K-ATPase appears to be primary driver (3 Na into developing cavity, 2 K into cell)
26
Q

Morphogenetic event III: blastocyst expansion

A
  • *Na,K-ATPase=primary driver
  • Requires a very efficient permeability seal that can be disrupted by drugs and break down the actin cytoskeleton or Ca2+ requiring adhesion molecules
  • *culminates in first differentiative event
27
Q

Blastocyst expansion: culminates in first differentiative event

A
  • Differentiation of:
    o ICM=embryo proper
    o Trophectoderm=extra-embryonic lineages
28
Q

What follows blastocyst expansion?

A
  • Hatching
    o ICM differentiates into hypoblast and epiblast (bilaminar disk)
29
Q

What does hatching require?

A
  • Release of enzymes (ex. strypsin) to break down matrices comprising zona pellucida
30
Q

Hatching is governed by 3 forces

A
  1. Growth and fluid accumulation within blastocyst
  2. Production of enzymes by trophectoderm cells to break down the matrices comprising the ZP
  3. Contraction of the blastocyst (=now free-floating embryo within lumen of uterus)
31
Q

Equine zona pellucida and capsule

A
  • Embryo does NOT hatch from ZP b/c ZP disintegrates around d7-d8 post-ovulation
  • D6.5: trophectoderm begins to secrete glycoprotein containing CAPSULE beneath ZP and capsule remains until d22 of pregnancy

ANIMAL PRODUCTION - Reproduction (17 decks)

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