Pre-fertilisation sperm events

Question 1

What is the structure of a spermatozoon?

Answer 1

Head:
- nucleus/DNA
- acrosome (enzymes)

Middle piece:
- packed full of mitochondrion
- ATP generation
- microtubules

Tail/flagellum:
- propels sperm

Question 2

Where does the first stage of sperm maturation take place?

Answer 2

Epididymis

Question 3

Explain the transportation and maturation of sperm in the epididymis

Answer 3

Transport takes 1-2 weeks
Acquire ability to be motile
Acquire ability to fertilise
Cytoplasmic droplet moves distally

Question 4

Label the testis

Answer 4

Question 5

What is the role of seminal plasma for sperm in the female tract?

Answer 5

Transport medium
Nutritional support
Buffering capacity - cervix tends to be acidic
Antioxidants
Proteins bind to sperm head
Prostaglandins cause female tract muscles to contract to aid movement of sperm

Question 6

Where is sperm deposited in cattle?

Answer 6

Cranial aspect of vagina

Question 7

Where is sperm deposited in the pig?

Answer 7

In uterus/cervix due to coiled penis and cervix

Question 8

What process prevents sperm from being lost after copulation

Answer 8

Semen coagulation - prevents further mating and retrograde transport, forms plug in rodents

Question 9

How is sperm lost after copulation?

Answer 9

Retrograde transport
Phagoctyosed after period of time (immune response to foreign body)

Question 10

How does sperm move in ejaculation?

Answer 10

Question 11

Describe the structure of the flagella of sperm

Answer 11

Question 12

How do dyneins cause movement of flagella in sperm?

Answer 12

Question 13

What types of sperm
tail abnormality are there?

Answer 13

Question 14

How does the cervix act as a barrier to sperm?

Answer 14

Mucous secretion:
- sialomucin (low viscocity)
- sulphomucin (high viscocity)
Removes non-motile sperm as vigorous sperm are required

Question 15

Describe the transport of sperm through the uterus to the uterine tube

Answer 15

Must pass through uterine-tubal junction
Rapid sperm transport:
- minutes after copulation
-due to elevated tone and motility of muscular layers of female tract due to elevated oestradiol and oxtocin, and due to prostaglandins in seminal fluid
Sustained sperm transport:
- in the hours after copulation
- these sperm fertilise the egg

Question 16

Describe the anatomy of the uterine-tubal junction

Answer 16

Tortuous and narrow lumen
Funnel
Requires vigorous sperm motility
Might close after period of time

Question 17

Describe the interactions of sperm in the uterine tube

Answer 17

Sperm bind to epithelial cells in the isthmus:
- aided by seminal proteins
- renders them immobile
- prolongs their lifespan
Sperm released around ovulation

Question 18

What is special about canine ejaculation?

Answer 18

Question 19

How does the canine uterus prevent polyspermy?

Answer 19

Sperm reservoirs in tips of uterine horns
Sperm binds to epithelial cells

Question 20

What is polyspermy?

Answer 20

multiple sperm fertilising a single egg -> wrong number of chromosomes

Question 21

Describe the process of sperm capacitation (2nd stage of maturation)

Answer 21

Enables sperm to be capable of fertilisation
- removal of decapacitation factors
- membrane destabilisation induced by ion movement
- detachment from the oviductal epithelium
- transient hyperactivity (exposure of surface proteins that can bind to oocyte, enables acrosome reaction)

Question 22

Describe sperm movement in fertilisation

Answer 22

Hyper-activated movement:
- asymmetric
- high amplitude
- straight in oviductal mucus
- whiplash

Question 23

Label this cumulus-oocyte complex

Answer 23

Question 24

Describe the process of sperm binding to the oocyte

Answer 24

• specific alignment of sperm and oocyte
• sperm binds to zona pellucida after crossing cumulus cells
• release of acrosomal hydrolytic enzymes
• enzymes digest ZP and form a localised small hole
• nucleus of sperm is release into oocyte

Question 25

What part of the oocyte prevents cross species reproduction?

Answer 25

The zona pellucida contains 3 glycoproteins (ZP 1, 2 and 3)
ZP3 - species specific through zona binding region

Question 26

What occurs to the oocyte after the sperm has bound to it?

Answer 26

Induces influx of Ca2+ ions and completion of meiosis II
Cortical (zona) reaction:
- contents of cortical granules released
- ZP hardens
- sperm receptors destroyed
- prevents polyspermy