1: Fertilization And Implantation

Question 1

Steps in oocyte release

Answer 1

1. LH surge -> follicle ruptures
2. Ovum and corona radiata ejected into peritoneum
3. Fimbriae sweep oocyte into oviduct

Question 2

How many sperm are released on ejaculation + how many reach ampulla?

Answer 2

300 million ejaculated, about 200 reach ampulla

Question 3

Qualification of infertile in terms of sperm per ejaculation

Answer 3

Less than 20 million sperm

Question 4

What female feature helps move sperm thru cervix/uterus?

Answer 4

Myometrium also contractions

Question 5

What causes myometrial contractions?

Answer 5

Increased estrogen near ovulation period

Question 6

Purpose of sperm binding epithelium while incapacitated

Answer 6

Slows capacitation process to extend the lifespan and give a higher probability of being in oviduct when egg is ovulated

Question 7

Two reasons for hyperactivation of sperm

Answer 7

1. Sperm detachment from epithelium of oviduct

2. Propels sperm thru outer layer of egg to reach plasma membrane

Question 8

Where does fertilization typically occur?

Answer 8

Ampulla of oviduct

Question 9

What is the corona radiata?

Answer 9

Expanded cumulus oopherus

Question 10

Acrosomal reaction

Answer 10

Sperm plasma membrane fuses with acrosomal membrane -> release of enzymes to digest ZP -> forms a hole that sperm can swim through

Question 11

What triggers cortical reaction?

Answer 11

Fusion of sperm and egg

Question 12

Function of cortical reaction

Answer 12

Prevent polyspermy

Question 13

During cleavage, what size does the embryo remain?

Answer 13

About 100um diameter

Question 14

Blastomeres

Answer 14

Totipotent individual cells of early embryo

Question 15

When does trophoectoderm form?

Answer 15

When outer cells of morula increase cell adhesions

Question 16

Examples of secretions from the blastocyst

Answer 16

Molecules that maintain pregnancy, promote implantation, placental development, immunosuppressive/regulatory factors, hCG, PAF, prostaglandins, ILs, etc.

Question 17

HCG structure

Answer 17

Closely related to LH

Question 18

Two cell types that secrete hCG in early embryo

Answer 18

Trophoblasts, syncytiotrophoblasts

Question 19

When is hCG measurable in blood?

Answer 19

About 8 days post ovulation

Question 20

Four major functions of hCG

Answer 20

1. Prevents involution of CL
2. Prevents menstruation
3. Leads to increased secretion of progesterone and estrogen
4. Stimulates trophoblast and placental growth and development

Question 21

Syncytiotrophoblast nuclei

Answer 21

Multi-nuclear and multicellular system

Question 22

Three hormones secreted by syncytiotrophoblasts

Answer 22

1. HCG
2. Progesterone (enough to maintain pregnancy without CL at week 10)
3. Angiotensin factors

Question 23

When does the syncytiotrophoblast become highly steroidogenic?

Answer 23

Week 10

Question 24

Two functions of decidualization of maternal stromal cells

Answer 24

1. Inhibits migration of implanting embryo

2. Inhibits embryo from invading myometrium (can cause hemorrhage)

Question 25

Most common site for ectopic implantation

Answer 25

Oviduct (called a tubal pregnancy)

Question 26

Two stages of implantation that are not controlled/dont occur in ectopic implantation

Answer 26

1. Invasion not controlled

2. Decidualization does not occur