Pre-fertilisation sperm events

Question 1

Describe the 3 parts of a spermatozoon

Answer 1

• Head- nucleus/ acrosome enzymes
• Middle piece- mitochondria rich/ lots of ATP generated/ microtubules
• Tail

Question 2

What is the role of the seminal plasma?

Answer 2

It isn’t essential for fertilisation but it aids transport and stimulates muscular activity in female tract. It also contains fructose- nutritional support for the sperm.

Question 3

Where is semen deposited in a cow?

Answer 3

The vagina

Question 4

Explain how the flagella moves to help with sperm locomotion

Answer 4

Central axoneme is highly ordered- made up of 9 outer microtubules. Dyneins are bound to each outer microtubule and slide the microtubules past each other. the structural links between the axoneme converts the sliding motion into a bending of axoneme.

Question 5

List the names of some sperm tail abnormalities

Answer 5

Coiled tail
Double midpiece
Folded tail

Question 6

What does capacitation allow and where does in occur?

Answer 6

Renders the sperm able to fertilise and occurs in the oviduct

Question 7

What are the four steps involved in capacitation?

Answer 7

1) Removal of decapacitation factors
2) Membrane destabilisation (ion movement)
3) Detachment from oviductal epithelium
4) Transient hyperactivity

Question 8

What is the zona pellucida made up of?

Answer 8

3 glycoproteins
ZP1= minor component
ZP2= structural component
ZP3= receptor ( species specific/ primary zona binding region/ promotes the acrosomal reaction)

Question 9

When does the acrosome reaction occur?

Answer 9

After capacitation and is initiated by the sperm binding to the zona pellucida

Question 10

Describe the acrosome reaction

Answer 10

Requires hyperactivity of the flagellum , involved acrosome hydrolytic enzymes and fusion of plasma membranes so that the spermatozoon nucleus can enter the oocyte.

Question 11

Describe oocyte activation

Answer 11

• Ovulation induces completion of meiosis 1
• BUT sperm binding to oocyte induced completion of meiosis 2
• Involves an influx of Ca2+ ions

Question 12

What induced meiosis 2 in the oocyte?

Answer 12

Sperm binding to the oocyte

Question 13

What is the cortical/ zona reaction?

Answer 13

When the ZP hardens and the sperm receptors are destroyed, blocks the other sperm.

Question 14

List the key stages of pre-fertilisation sperm events

Answer 14

1- transverse the cervix
2- transport through uterus to oviduct
3- oviductal storage
4- capacitation
5-binds to the oocyte
6-acrosome reaction
7- fusion of nuclei