L13

Question 1

What are the 4 requirements that occur for capacitation?

Answer 1

1. ZP3 receptor expression inc to binds sperm head to zona pellucida
2. Decapacitation factor washed away/removed
3. Changes to acrosome (now capable of releasing proteolytic enzymes to break down zona pellucida, hyaluronidase to break down granulosa cells)
4. Dec cholesterol??

Question 2

Where is decapacitation factor produced and its fxns?

Answer 2

1. Produced in EPIDIDYMIS
2. Prevents capacitation rxn
3. Suppresses motility

Question 3

Fxn of cholesterol during capacitation/decapacitation?

Answer 3

Decapacitation

• high conc in testicular fluid
• hardens the acrosomal cap

Capacitation
- cholesterol environment lvls dec allowing acrosomal cap to weaken and penetrate ovum??

Question 4

Fxn of ZP3 receptor?

Answer 4

Binds sperm head to zona pellucida

Question 5

How is the female reproductive tract involved in capacitation?

Answer 5

1. uterine FLUIDS wash away decapacitation factor
2. loss of high CHOLESTEROL environment weakens acrosomal cap
3. sperm become permeable to Ca2+ – activates whip like activity of flagella in tail
4. involves inc in intracellular pH and [Ca2+]
5. involves HCO3- and sAC (soluble adenylyl cyclase)
6. will discuss IUI and IVF later; both involve washing of sperm

Question 6

When does fertilization occur?

Answer 6

Day 16-17

Question 7

What are the 9 steps in fertilization?

Answer 7

DAY 16-17
1. HYALURONIDASE (from acrosome) breaks down GRANULOSA cells and SPERM binds to ZP3 glycoprotein. (ZP is x-linked ZP1, ZP2, ZP3)

2. Sperm-ZP3 interaction initiates acrosomal rxn – acrosomal MEMBRANE DISRUPTED and PROTEOLYTIC contents released.

3-4. Action of acrosomal ENZYMES and TAIL THRASHING allows sperm to penetrate ZP and FUSE w/oocyte MEMBRANE. CYTOPLASMIC portions of the sperm ENTER the OOCYTE (not entire sperm itself)

5-6. Intracellular Ca released from intracellular STORES initiate the CORTICAL RXN-exocytosis of SUB-membrane GRANULES that contain ENZYMES that HARDEN the ZP – ensures only a SINGLE SPERM penetrates the ovum. NUCLEUS of ovum completes second MEIOTIC division (haploid).

7. Sperm NUCLEUS DECONDENSES and TAIL DEGENERATES.
8. Male and female HAPLOID PRONUCLEI FUSE – DIPLOID ZYGOTE. Fertilization is complete.
9. Fertilized OVUM is TRANSPORTED (cilia, fluid and weak uterine tube contractions) to UTERUS [3 days] during which time several stages of cell DIVISION occur – BLASTOCYST (~100 cells). Secretions from uterine tube nourish the blastocyst.

Question 8

When does implantation occur?

Answer 8

Day 20

Question 9

Describe the steps of implantation

Answer 9

• Implantation occurs ~day 20

- Site of fertilization is the