Embryology 1

Question 1

What are the three phases of pregnancy?

Answer 1

Pre-embryonic phase 0-3 weeks

Embryonic phase 4-8 weeks

Foetal phase 9-40 weeks

Question 2

What are the cells that produce the sperm cells and the ova?

Answer 2

Spermatogonium

Oogonium

Question 3

Where are the Spermatogonium and Oogonium found?

Answer 3

Gonads

Question 4

What is the contents of a sperm cell?

Answer 4

22 chromosomes, 1 X, or 1 Y

Question 5

What is the contents of an ovum?

Answer 5

(22+X)

3 polar bodies

Question 6

What fuses to from the zygote?

Answer 6

(pro)Nucleus of sperm enters and fuses with (pro)nucleus of ovum

Creates diploid cell, ZYGOTE

Question 7

What part of the sperm enters the ovum?

Answer 7

Only the nucleus

Rest of the cell is left behind

Question 8

What happens during week one of pre-embryonic phase?

Answer 8

• Zygote forms, divides to form blastocyst
• Moves through uterine tube, to reach uterine cavity

Question 9

Why are zygotes always unique?

Answer 9

No two sperm/ova are the same

Question 10

Which parent is mitochondrial disease inherited from?

Answer 10

Mother

Question 11

What does a zygote become after dividing?

Answer 11

Morula

Solid ball of cells

Question 12

What day is a blastocyst formed?

Answer 12

Day 5/6 of pre-embryonic phase

Question 13

Why is the blastocystic cavity formed?

Answer 13

Increasing number and size of cells makes it more difficult to get nutrition to central core of cells

Question 14

How is the blastocystic cavity formed?

Answer 14

• Cells accumulate at one end to form an inner cell mass.
• The outer lining of cells is called the trophoblast.

Question 15

How long does the first cell division take?

Answer 15

36 hours

Question 16

What happens on day 5/6?

Answer 16

Blastula has formed

Reaches uterine cavity ready to implant in it

Question 17

What is required for the the dividing zygote/ morula/ blastocyst fallopian tube to move and reach the uterine cavity?

Answer 17

Requires healthy ciliated epithelium

Question 18

When is ectopic pregnancy likely to occur?

Answer 18

• Cilia function is abnormal
• Pregnancy occurs in uterine tube
• Complications include rupturing of uterine tubes

Question 19

What is the endometrium?

Answer 19

Mucous membrane lining uterus

Thickens during menstrual cycle in preparation for possible implantation of an embryo

Question 20

When does the placenta start to develop?

Answer 20

Start by day 6 of 1st week, when implantation occurs in the uterine endometrial layer

Question 21

What starts to form at week 2?

Answer 21

• Sacs, membranes and cord to nourish human conceptus (baby) start to form
• Cells that later form embryo form a bilaminar disc

Question 22

What is the role of the chorion?

Answer 22

Burrowing

Question 23

What cells are initially called to trophoblasts?

Answer 23

Cells that form the outer cell mass

Question 24

What forms the chorion?

Answer 24

trophoblast

Question 25

What does the Chorion do?

Answer 25

* Implantation process (chorionic villi) * Forms part of the placenta * Secretes human Chorionic gonadotropin (HCG) (used to detect pregnancy)

Question 26

What is the function of HCG?

Answer 26

Tells ovary to continue producing oestrogen and progesterone so endometrium does not get shed

Question 27

What is used to test for pregnancy?

Answer 27

HCG Present in urine

Question 28

What is the decidua basalis?

Answer 28

part of the endometrium deep to the implanted conceptus.

Question 29

What is the decidua?

Answer 29

Area in endometrium where blastocyst implants

Question 30

Which part of the endometrium contains more blood vessels?

Answer 30

Decidua basalis

Question 31

When does HCG content increase until?

Answer 31

Increase till around 12 weeks gestation

Question 32

What is the change in structure of the inner cell mass?

Answer 32

Cells of the inner cell mass form a 2–layered flat disc called the BILAMINAR DISC

Question 33

What is the name of the two cell cavities formed by the inner cell mass?

Answer 33

2 cavities now begin to form * Amniotic cavity (A) * Yolk sac (Y)

Question 34

What are the names of the different layers of the Bilaminar disk

Answer 34

Top - Epiblast Bottom - Hypoblast

Question 35

What is the name of the abbreviated structures?

Answer 35

AC – Amniotic cavity CC – Chorionic cavity AL – Allantoic cavity YS – Yolk sac

Question 36

How does the chorion handle the blood of the embryo?

Answer 36

Prevents maternal blood and embryo blood to mix?

Question 37

Look

Answer 37

Question 38

What are the main functions of the placenta?

Answer 38

Main functions: 1. Foetal nutrition 2. Transport of waste and gases 3. Immune etc

Question 39

Which part of the placenta is smooth?

Answer 39

Foetal part and surface: smooth with foetal blood vessels and end of umbilical cord

Question 40

Which part of the placenta is rough?

Answer 40

Maternal part: Decidua basalis of endometrium Rough and has maternal blood vessels

Question 41

When is the placenta mature?

Answer 41

By 18-20 weeks

Question 42

How are fraternal/dizygotic twins formed?

Answer 42

Question 43

How does an identical twin/monozygotic twin formed?

Answer 43

Question 44

Summary of Weeks 1 and 2

Answer 44