Fertilisation

Question 1

Whereabouts do sperm become capacitated?

Answer 1

In the female reproductive tract. (oestrogen primed uterus or oviduct)

Question 2

What are the two components of capacitation?

Answer 2

1. Change is the movement characteristics to become hypermotile (change to whiplashing beats of the tail that push the sperm forward in bursts)
2. Change is the surface membrane properties that allows sperm to be responsive to signals from the oocyte. This then induces the acrosome reaction

Question 3

What happens in the acrosome reaction?

Answer 3

1. Acrosome swells and its membrane fuses with the outer plasma membrane
2. Vesiculated appearance is created and the contents of the acrosomal vesicle become exteriorized.
   Increase in intracellular calcium and cAMP.
3. Rise in intracellular pH

Question 4

What agent is thought to be responsible for inducing the acrosome reaction?

Answer 4

Zona Pellucida protein 3

Question 5

What enzyme, present in the sperm breaks down the hyaluronic acid holding the cummulus cells together?

Answer 5

Hyaluronidase

Question 6

Describe what role progesterone is thought to play in sperm capacitation

Answer 6

Stimulates an influx of progesterone into the spermatazoa leading to the stimualation of adenyl cyclase and a rise in cAMP.
Progesterone is carried in the cummulus cells and it is though progesterone might make the sperm acrosome more leaky and likely to release hyaluronidase

Question 7

What protein is thought to hold the spermatazoon and zona in contact?

Answer 7

Zona Pellucida protein 2

Question 8

What protein does the inner acrosomal membrane (revealed by the acrosome reaction) have an affinity for?

Answer 8

Zona pellucida protein 2

Question 9

Why is it important for the acrosome reaction to occur close to the oocyte?

Answer 9

After this reaction has occured the sperm have a very short life span

Question 10

Which ZP protein is thought to be the sperm receptor?

Answer 10

ZP3

Question 11

How long after ovulation can the egg survive for?

Answer 11

12 - 24 hours

Question 12

How long after ejaculation will the first sperm arrive in the oviduct?

Answer 12

30 mins

Question 13

What are Catsper channels?

Answer 13

• Ion channels that form voltage gated Ca2+ channels that are specific to sperm. As the sperm encounter the more alkaline environment of the female reproductive tract the CatSper channels become activated by the altered ion concentration. - They control the entry of positively charged calcium ions into the cells which is essential for sperm hyperactivation and male fertility.
• They are found only on the principal piece of the sperm flagellum
• CatSper channels are essential for male fertility and mutations in catsper 1 and 2 have been identified in infertile individuals.
• Progesterone influences the opening of CatSper channels