3.3 Fertilisation and Blastocyst Development

Question 1

What challenges to the sperm have to face in the female tract?

Answer 1

• avoid retrograde transport
• transverse the cervix
• travel through the uterus
• travel through the oviduct
• attain the ​capacity to fertilize: capacitation,, hyperactivation, acrosome reaction

Question 2

Where do sperm take palce?

Answer 2

This is dependent on the ​species

Question 3

retrograde transport: cow

Answer 3

60% sperm lost within 12 hrs

Question 4

retrograde transport: human

Answer 4

99% sperm lost in human

Question 5

How do pigs avoid retrograde transport?

Answer 5

intra uterine semen deposition of huge 1/2 liter ejaculate
- corkscrew penis screws through cervix​ and deposits it directly in uterus

Question 6

How do the horse and dog avoid retrograde transport?

Answer 6

semen squirted through the cervix at copulation

** dog maintain mating position, high pressure

Question 7

species with viscous/gel fraction of seminal plasma acts to “plug” tract

Answer 7

horse, pig, rodent

Question 8

Answer 8

Question 9

Answer 9

Question 10

The head: acrosome

Answer 10

contains enzymes that have to dissolve through the zona pellucida which surrounds the oocyte at fertilization

Question 11

Where does the energy come from to assist the whiplashing tail for motility

Answer 11

midpiece: mitochondria

Question 12

sperm motility:

Answer 12

• motile
• viscous fluid currents: assists in movement through the uterus
• uterine contractions: assist fluid current​

Question 13

sperm tail:

Answer 13

• energy production (midpiece mitochondrial​ sheath supplies ATP)
• propulsive appartus (axoneme)

Question 14

evaluation of sperm motility:

Answer 14

• computer assisted semen analysis (CASA)
• assesses the quality of motility
• ## identify fertile sperm

Question 15

What makes up the majority of the sperm head?

Answer 15

nucleus

Question 16

equatorial segment of sperm head:

Answer 16

site of sperm-egg​ binding

Question 17

sperm do not attack rival ejaculates​, instead they

Answer 17

instead sperm display co-operation

Question 18

Sperm from a single male will co-operate to gain

Answer 18

a competitive advantage over sperm from another​ male

Question 19

when does inter-male sperm competioion occur?

Answer 19

in species where multiple males mate wit the same female

Question 20

wood mouse sperm train:

Answer 20

• sperm head hook attached​ to neck region
• hook deployed in the presence of rival male’s sperm
• sperm form trains to increase motility
• over 2mm long consisting of thousands of sperm
• train motility 2x speed of single sperm

Question 21

echidna sperm form?

Answer 21

sperm bundles (more tails)
- gain an advantage
- faster motility

Question 22

morphology of sperm is realted​ to?

Answer 22

genetic viability

Question 23

does abnormal morphology matter in natural mating?

Answer 23

abnormal morphology will be selected out by the ​female reproductive tract

-affects the ​ability to fertilize
-natural mating involves sperm competition
- natural selection and survival of the fittests

Question 24

Inta cytoplasmic sperm injection (ICSI):

Answer 24

• modified IVF
• no natural selection
• used with abnormal sperm
• sperm abnormality reflects gentic problems

Question 25

sites of semen deposition affect?

Answer 25

retrograde transmission of sperm

Question 26

spe​rm cooperate to overcome?

Answer 26

competition between males

Question 27

sperm motility is facilitated by the

Answer 27

tail and mitochondria midpiece

Question 28

sperm movement in 2 phases:

Answer 28

• rapid movement phase
• sustained transport phase

Question 29

rapid movement​ phase:

Answer 29

• sperm reach oviducts within minutes
• unable to fertilize the oocyte

Question 30

sustained transport​ phase:

Answer 30

sperm undergo:
- capacitation
- hyperactivation
- acrosome reaction

Question 31

freshly ejaculated sperm cannot fertilize oocyte, so they must undergo

Answer 31

capacitation

Question 32

Capacitation:

Answer 32

progressive destabilization​ of plasma membrane
- glycoprotein molecule coating sperm head removed
- exposure of zona pellucida binding proteins
- allows sperm to bind to the oocyte at fertilization
- surface change altered: may attract sperm to oocyte
- membrane fluidity increased to aid breakdown of acrosome

Question 33

Hyperactivation:

Answer 33

• capacitated sperm exhibit hyperactivated motility
• strong, wide amplitude, whiplashing tail beats
• increase Calcium leads to elvated cAMP

Question 34

___ required to swim through the viscous environment​ within the oviduct

Answer 34

increased force

Question 35

binding to zona pellucida initiates:

Answer 35

acrosome reaction
- fusion of sperm plasma membrane and outer acrosomal membrane
- release of enzymes to digest the zona pellucida
- exposure of equatorial segemnt for oocyte fusion

Question 36

before acrosome reaction:

Answer 36

all membranes intact

Question 37

during acrosme reaction:

Answer 37

• plasma membrane fuses with outer acrosomal membrane
• fusion causes vesiculation producing pores
• release of hyaluronidase and acrosin

Question 38

after acrosome reaction:

Answer 38

• vesicles lost
• inner acrosomal membrane and equatorial segment exposed

Question 39

acrosomal enzymes digest:

Answer 39

small hole in zona pellucoda

Question 40

penetration of the zona pellucida is a ___ process

Answer 40

rapid

Question 41

sperm move into perivitelline space between

Answer 41

zona and oocyte plasma membrane

Question 42

What molecules are used to bind to zona pellucide?

Answer 42

ZP3

Question 43

Sperm in perivitelline space surrounded by plasma membrane microvilli

Answer 43

plasma membrane microvilli

Question 44

Sperm equatorial segment fuses with

Answer 44

oocyte plasma membrane, Sperm is engulfed

Question 45

Cortical granules released into

Answer 45

perivitelline space