Fertilization

Question 1

Following deposition of semen

Answer 1

There is some retrograde loss of semen (backflow)

Question 2

Series of steps after insemination

Answer 2

Transverse the cervix, travel through uterus and into oviduct, find the COC, penetrate cumulus of cells and bind ZP, undergo acrosome reaction, penetrate ZP, fuse with oocyte PM

Question 3

High E2 during estrus increases blood flow to repro tract

Answer 3

More neutrophils in mucosal layers and lumen - phagocytosis of foreign material

Question 4

At time of insemination

Answer 4

Spike in endometrial neutrophils that diminish over 48h

Question 5

Persistent Post-Breeding Endometritis (PPBEM)

Answer 5

Overly inflamed endometrium following insemination that hinders or prevents embryogenesis

Question 6

High E2 increases….

Answer 6

Mucus production and muscular tone of repro tract, both of which aid transport of sperm through uterus and oviducts

Question 7

Passage through cervix is selective process

Answer 7

Helps select more viable, healthy/motile sperm

Question 8

Folds of cervix

Answer 8

Barrier and a reservoir for spermatozoa

Question 9

Sulfomucin

Answer 9

Produced by epithelium in apical portion of cervical crypts, has high viscosity and helps wash sperm out of repro tract

Question 10

Sialomucin

Answer 10

Produces in basal portion of crypts, low viscosity and allows sperm to swim towards uterus

Question 11

Prostaglandin

Answer 11

Produced by sperm induce contraction of myometrium in conjunction with E2

Question 12

Rapid Transport Phase

Answer 12

Sperm reaches oviducts within a few mins of insemination but is not viable for fertilization

Question 13

Sustained Transport Phase

Answer 13

Trickle of sperm from reservoirs, these sperm are more likely to successfully fertilizle oocyte b/c sperm must reside in female repro tract

Question 14

Spermatogenesis

Answer 14

Head of sperm is covered with glycoproteins and sterols that distinguish it as a foreign cell from rest of body

Question 15

Ejaculation

Answer 15

Proteins of seminal plasma coat head of sperm cells and prevent immune system destruction by male repro tract

Question 16

Capacitation

Answer 16

Seminal plasma proteins stripped from sperm cell surface, exposing binding sites and increases membrane fluidity
-gradual process occurring along path of cervix to oviducts

Question 17

Uterotubal Junction

Answer 17

Regulates passage of sperm into oviduct

Question 18

Smooth muscle and Vascular beds

Answer 18

Compresses lumen of oviduct to avoid excessive number of sperm and polyspermy of oocytes

Question 19

Lower Isthmus

Answer 19

Has tunnels in mucosa for sperm docking - storage and preservation of sperm

Question 20

After release from resevoir

Answer 20

Sperm must still move from isthmus to ampulla

Question 21

Hyperactivation

Answer 21

Required for penetration of viscoelastic substances and for penetration of ZP

Question 22

Zona Pellucida

Answer 22

Membrane composed of structural and sperm protein receptor glycoporteins

Question 23

2 components that bind ZP3

Answer 23

1: zona binding region - promotes physical attachment to ZP
2: acrosomal reaction promoting region: binding initiates acrosomal reaction

Question 24

Acrosomal Reaction

Answer 24

PM over acrosome fuses with outer acrosomal membrane (OAM) - pores form and acrosomal enzymes are secreted - enzymes digest a hole in ZP

Question 25

Cortical Reaction

Answer 25

During membrane fusion, exocytosis of cortical granules releases contents into PS

Question 26

Zona Block

Answer 26

Contents of cortical granules change ZP so that more sperm cannot penetrate it

Question 27

Vitelline Block

Answer 27

Contents reduce ability of oocyte RM to fuse with sperm

Question 28

After membrane fusion

Answer 28

Nucleus of sperm decondenses into cytoplasm of oocyte by reduction of disulfide cross-links

Question 29

Before Fertilization

Answer 29

Oocyte nucleus is diploid (arrested in metaphase 2) and capacitated sperm nucleus is haploid

Question 30

After Fertilization

Answer 30

Maternal and paternal pronuclei (haploid nuclei of fertilized gametes) form

Question 31

Oocyte

Answer 31

Influx of Ca2+ induces oocyte activation and completion of meiosis 2 and expulsion of 2nd polar body - formation of maternal pronucleus

Question 32

Spermatozoon

Answer 32

Cytoplasmic environment of newly fertilized oocyte induces decondensation of chromosomes - formation of paternal pronucleus

Question 33

Syngamy

Answer 33

Fusion of pronuclei to form a single diploid nucleus, last step before embryogenesis