Fertilisation

Question 1

What function do the cumulus cells do post ovulation?

Answer 1

They regulate the intracellular oocyte pH by acting as a buffer as the oocyte goes down the fallopian tube

Question 2

Where does fertilisation usually occur?

Answer 2

Ampulla of fallopian tube

Question 3

what is roughly the maximum size a follicle
reaches?

Answer 3

25mm

Question 4

How does ovulation occur?

Answer 4

Wall of the ovary thins due to stretching.
Matrix mellatoproteinases also break down the ovary wall.

Question 5

Describe the interaction between the cumulus oocyte complex and the oviduct fimbrae

Answer 5

The cumulus has a transient interaction with the fimbrae where the stick and then are released when the fimbrae waft them down stream

Question 6

Describe the function of the hyaluronic acid molecules in the COC

Answer 6

The flexibility and negative charge of the molecules provides high elasticity and softness to the complex that allows the COC to softly interact with the cilia tips and doesn’t damage the cilia

Question 7

What is rheotaxis?

Answer 7

The ability sperm have to orientate themselves and swim upstream against fluid flow
(although questioned)

Question 8

Name 2 reservoirs that sperm get held at?

Answer 8

• cervix
  -isthmus of the oviduct (can stay for 5-7days)

Question 9

How are sperm released from the transient interaction with oviductal cilia?

Answer 9

Modification of protein-protein interaction
Hyperactivation

Tend to be released in batches - we don’t know how

Question 10

What hormone do cumulus cells release?

Answer 10

Progesterone

(May cause hyperactivation of sperm)

Question 11

Name the proteolytic enzyme found in the acrosome

Answer 11

Acrosin

Question 12

Describe the classic model for sperm cumulus interaction

Answer 12

• The sperm contains hyaluronidase which helps it to penetrate the cumulus matrix
• The sperm fuses with the ZP and undergoes an acrosome reaction to break down the ZP and penetrate through

Question 13

what is the oolemma

Answer 13

membrane around the oocyte

Question 14

What proteins on the ZP bind sperm?

Answer 14

ZP3/ ZP4

Question 15

Is JUNO a protein/receptor on the oolemma or sperm

Answer 15

oolemma

Question 16

Is IZUMO1 present on the sperm membrane or oolemma?

Answer 16

Sperm

Only on inner membrane so non acrosome reacted sperm won’t express and, therefore, won’t be able to interact or fertilise

Question 17

Describe post fertilisation events and the oocyte development

Answer 17

Post fertilisation the oocyte is activated by PLCz enzyme from the sperm.

This breaks down membrane lipids which cause an increase in intracellular calcium.

This allows meiosis II to begin completion as the calcium allows the first cell division to occur.

Question 18

At what point is the oocyte called a zygote?

Answer 18

When it is fertilised with sperm

Question 19

Which sperm don’t contain PLCz?

Answer 19

Those with globozoospermia (sperm without an acrosome) - these have a round head.