Capacitation and early fertilisation

Question 1

What is capacitation?

Answer 1

The biochemical process that prepares sperm to fertilise an egg

Question 2

What 3 major complications do sperm face in the vagina?

Answer 2

• gravity
• low pH
  -Immune cells

Question 3

What fluid is sperm ejaculated in first (probably the one that fertilises)

Answer 3

Prostatic fluid

Question 4

What semen fluid coagulates and what are the proteins that cause this?

Answer 4

Seminal vescile fluid
- semenogelin 1 and 2 + Zinc

Question 5

What breaks down coagulum and what is this process called?

Answer 5

Prostate specific antigen - PSA
Liquefaction

Question 6

What is cervical mucous made of?

Answer 6

• water
• glycoproteins (mucins)
  -ions and bicarbonate
• immunoglobulins

Question 7

What factors influence the sperms ability to penetrate cervical mucous?

Answer 7

• during ovulation cervical mucous is thinner and easier to get through (oestrogen = more aquaporins)
• non-ovulatory phases mucous is thicker and more acidic (progesterone)
  -sperm kinetics and morphology

Question 8

Describe the histology of the cervix

Answer 8

Stroma is made from collagen matrix and fibroblasts

Columnar epithelial cells produce mucous

Question 9

Is the fluid composition in the cervix homogenous?

Answer 9

No

Cervical mucous creates a preferred route due to muoucs thickeness and immune cells

Question 10

Describe the composition of epidiymal fluid and the state of sperm

Answer 10

Low in Na+, Cl-, HCO3 and low pH

This keeps the sperm in a quiescent state.

Question 11

What is cervical mucous scrubbing?

Answer 11

It’s a form of selection process. It selectively allows sperm with a certain morphology and motility pass through the cervix

Question 12

What is calcium useful for in the sperm?

Answer 12

It’s required for hypermobility
It also helps protect against ROS

Question 13

What does vit E (Tocopherol) do to help protect sperm

Answer 13

Vit E is an antioxidant. It protects the sperm against ROS produced by leukocytes. It can be taken off the sperm membrane sometimes during cervical scrubbing - sperm require enough calcium in this case to manage against ROS without the vit E

Question 14

What do sperm loose from their membrane when going through the uterine cavity?

Answer 14

Cholesterol (probably due to albumin)

Question 15

What protein does the endometrium express to help calcium enter into the sperm

Answer 15

It expresses Sialic acid binding protein (SABP) which binds to the appropriate receptor on the sperm membrane and allows calcium into the cell

Question 16

At what point in the sperms journey does capacitation begin?

Answer 16

At the level of the epididymis

Question 17

Does HCO3 concentration increase along the length of the epidimus?

Answer 17

Yes

Question 18

Describe what fluids/ areas have high levels of HCO3

Answer 18

Seminal fluid and female reproductive tract

Question 19

Describe the importance of HCO3 for sperm capacitation in the epipidiymis

Answer 19

• HCO3 enters the cell and binds to SACY (soluble Adenylyl Cyclase)
• This converts ATP to cAMP
• This binds to PKA
  -PKA phosphorylates Ser and Thr which are present in the tail

Also changes in pH open Catsper channel - this allows calcium into the cell and activates it

Question 20

Describe the slow events of sperm capacitation in the uterus.

Answer 20

-Cholesterol is removed from the sperm membrane in the uterus
- This changes the fluidity of the membrane and activates channels allowing HCO3 and Ca2+ into the cell
-these bind to and activate SACY
- SACY converts ATP - cAMP
-This binds to PKA and phosphorylates tyrosine proteins
- These are important for hyperactivation of sperm