Session 2

Question 1

Describe what happens in fertilisation

Answer 1

• Oocyte is released from the ovary
• Travels along the Fallopian (uterine) tube
• Is fertilised by sperm in the ampulla of the fallopian tube
• Fertilised oocyte is called the zygote
• Ideally, the fertilised oocyte will implant itself ideally high up on the posterior uterine wall (marked in red)O

Question 2

What are the walls of the uterus lined with?

Answer 2

• A nice rich, glandular vascular lining called the endometrium
• Ideally primed to accommodate blastocyst once that developmental stage has been achieved

Question 3

How long is an oocyte viable for?

Answer 3

1 day

Question 4

How long is a sperm viable for?

Answer 4

Up to 3 days inside the female reproductive tract

Question 5

What is the fertile window?

Answer 5

• That period up to 3 days prior to ovulation

- 3 days afterwards

Question 6

What happens at the end of the first week?

Answer 6

Implantation just begins - it’s certainly not complete

Question 7

What does this diagram summarise? Label it

Answer 7

fertilisation and implantation

Question 8

What happens at the end of week 2?

Answer 8

• Implantation complete
• Day 9-10
• about 10 days after fertilisation, endometrium has been breeched
• That breech has been filled up with a fibrin plug
• The Syncytiotrophoblast is continuing to elaborate and make contact with the glands and vessels that have been prepared within that endometrium
• Beginning to make access to the maternal circulation and maternal tissues for further support

Question 9

Label the parts of the completion of implantation

Question 10

What would you use to describe human implantation?

Answer 10

• Interstitial
• Meaning the conceptus (fertilised egg, embryo or foetus) is embedded within the endometrium
• Also the number of barriers between the foetal and maternal circulation is trimmed back to the bear minimum so it’s just the very least that is required to stop mixing of circulations

Question 11

What does interstitial implantation result in?

Answer 11

- The uterine epithelium is breached and the conceptus implants within the
uterine stroma (so it's surrounded by endometrium)

Question 12

what is established within the placenta when implantation occurs?

Answer 12

• maternal blood flow, allowing support of the embryo from maternal circulation
• the basic structural unit of materno-fetal exchange

Question 13

What is the basic structural unit of materno-fetal exchange?

Answer 13

The chorionic villus (insert image)

Question 14

what are the 4 conditions linked to implantation defects?

Answer 14

1) IUGR (Inter Uterine Growth Restriction - the baby doesn’t grow optimally)
2) pre-eclampsia ( has it’s roots in a defect in implantation)
3) ectopic pregnancy
4) placenta praevia

Question 15

Which 2 implantation defects are grounded in the early stages of implantation?

Answer 15

• Eptopic pregnancy
• Placents praevia

(the other 2 are related to events that are happening after the first week of development through to the end of the first trimester)

Question 16

What is ectopic pregnancy?

Answer 16

implantation of the fertilized egg at any site other than the normal uterine body

Question 17

Where does Ectopic pregnancy most commonly occur?

Answer 17

in the fallopian tube

Question 18

where else can ectopic pregnancies occur?

Answer 18

• Ovarian or Peritoneal

Ovaries or abdomen

Question 19

how severe can ectopic pregnancies be?

Answer 19

they can very quickly become a life-threatening emergency

• Mainly because the narrow Fallopian tube cannot distend largely and with the progression of the pregnancy, the Fallopian tube ruptures
• This can cause heavy internal bleeding and abdominal pain

( As the implantation process is invasive and if that invasion involves one off the many large blood vessels in the pelvis, it leads to hemmorage)

Question 20

What is placenta praevia?

Answer 20

implantation in the lower uterine segment (too far down) causing the placenta to cover all or part of the cervix during the last months of pregnancy

Question 21

What can placenta praevia cause?

Answer 21

hemorrage in pregnancy

Question 22

what is an sign of placenta praevia?

Answer 22

bleeding

Question 23

what is required due to placenta praevia?

Answer 23

what is required due to placenta praevia?

Question 24

Name some risk factors of ectopic pregnancy

Answer 24

• Assisted reproductive treatments such as IVF

- Women becoming pregnant using progesterone-only contraceptive methods

Question 25

Name some common symptoms of ectopic pregnancy

Answer 25

• Vaginal bleeding
• Abdominal pain
• Pelvic Tenderness

Question 26

Name some risk factors for placenta praevia

Answer 26

• Advancing maternal age

- Smoking

Question 27

Name some symptoms for placenta praevia

Answer 27

• Painless bleeding string after 28th week

Question 28

What does the zygote get converted to?

Answer 28

zygote - morula - blastocyst

Question 29

Can you explain the derivation of syncytiotrophoblast - what it is and where it comes from

Answer 29

Outer layer of chronic villi, part of the placenta

Question 30

Can you explain the derivation of cytotrophoblast - what it is and where it comes from

Answer 30

The inner layer of chronic villi, part of the placenta

Question 31

Give the order of events that occur in the first 2 weeks of the embryonic period

Answer 31

• fertilisation and implantation
• 3rd week, we begin gastrulation
• Sets things up for neurulation and segmentation
• Which together contribute to folding of the embryo