Embryology

Question 1

What cell do gametes begin as in men?

Answer 1

• Spermatogonium

Question 2

What cell do gametes begin as in women?

Answer 2

• Oogonium

Question 3

Are spermatogonium and oogonium haploid or diploid?

Answer 3

Diploid

Question 4

What is the possible genotype of sperm produced through meiosis of a spermatogonium?

Answer 4

• 22 + X - 22 + Y

Question 5

What is the possible genotype of ova produced through meiosis of an oogonium?

Answer 5

• 22 + X

Question 6

What is meant by facilitation with reference to fertilisation?

Answer 6

• Hundreds of sperm needed to reach the ovum for one to get through into it. Without the hundreds the one won’t get through

Question 7

What is the only thing the sperm passes onto the egg?

Answer 7

Genetic material

Question 8

What is the name of the diploid fertilised cell?

Answer 8

Zygote

Question 9

What does the zygote do as it passes through the oviduct?

Answer 9

• Divides to form a morula (a solid ball of cells)

Question 10

What happens to the cells inside the morula as it’s size increases?

Answer 10

Increasingly more difficult to get nutrients to them

Question 11

What develops in response to the middle cells “starving”?

Answer 11

Blastocystic cavity

Question 12

What else forms around the blastocystic cavity and the mass of cells?

Answer 12

Trophoblast

Question 13

When does the blastocyst reach the uterus?

Answer 13

Day 5

Question 14

How does the blastocyst move through the oviduct?

Answer 14

• Has ciliated mucousal epithelium in it - These have a ciliary beat that allows the blastocyst to be transported

Question 15

What happens if the blastocyst doesn’t reach the uterus in time before implantation?

Answer 15

• It will imbed in the oviduct - Ectopic pregnancy

Question 16

Which parent is the genetics for the mitochondria and other organelles inherited?

Answer 16

The mother

Question 17

What are examples of mitochondrial disease that come from inherited defective mitochondria?

Answer 17

• Leber’s optical neuropathy

Question 18

What happens at the beginning of week 2?

Answer 18

• Blastocyst burrows into the endometrium

Question 19

What part of the blastocyst do cells that form the embryo come from?

Answer 19

The inner cell mass

Question 20

What happens to the trophoblast in week 2?

Answer 20

• It divides into 2 layers of cells

Question 21

What is the divided trophoblast known as?

Answer 21

Chorion

Question 22

What does the chorion develop to stick to the endometrium

Answer 22

Finger like villi known as chorionic villi

Question 23

What does the chorion eventually become a part of?

Answer 23

The placenta

Question 24

What hormone does the chorion secrete?

Answer 24

Human Chorionic Gonadatrophin

Question 25

What clinical role can human chorionic gonadotrophin play?

Answer 25

Can be used to detect pregnancy

Question 26

What effect does human chorionic gonadotrophin have on the ovary?

Answer 26

Inhibits it from secreting a surge of lutenising hormone that causes the endometrium to be shed

Question 27

What is the endometrium now known as when the blastocyst has embedded into it?

Answer 27

Decidua

Question 28

What is the area where the blastocyst is embedded known as?

Answer 28

Decidua basalis

Question 29

How does the decidua basalis differ to the rest of the endometrium?

Answer 29

More vascular

Question 30

What happens to the inner cell mass during the second week?

Answer 30

- Flattens - Forms two layers

Question 31

What are the two layers formed by the inner cell mass called?

Answer 31

- Epiblast and hypoblast

Question 32

What is the cavity touching the epiblast called?

Answer 32

Amniotic cavity

Question 33

What is the cavity touching the hypoblast called?

Answer 33

Yolk sac

Question 34

Name the coloured areas

Answer 34

- Yellow area = yolk sac - Blue cavity = amniotic cavity - Black outline = Chorion - Brown cavity = allantoic cavity

Question 35

What is the function of the allantoic cavity?

Answer 35

Waste cavity

Question 36

What is the function of the chorion at this point?

Answer 36

Seperate embryionic blood and maternal blood to stop rejection

Question 37

How is waste transferred out through the chorion?

Answer 37

Diffusion alone

Question 38

What is the function of the placenta?

Answer 38

Provides the foetus with nutrition and allows diffusion from the allantoic cavity

Question 39

How do non identical twins form?

Answer 39

- Di zygotic - 2 ova released fertilised by a sperm each

Question 40

How do identical twins form?

Answer 40

- Monozygotic - Zygote divides two form two zygotes that each develops into an embryo with the same genetic makeup

Question 41

What forms in week three?

Answer 41

The germ layers

Question 42

When looking down on the epiblast, a small trench forms down the middle, what is this called?

Answer 42

Primitive Streak

Question 43

What happens to the cells in the primitve streak?

Answer 43

They enter the space inbetween the hypoblast and the epiblast

Question 44

What effect do the epiblast cells have on the hypoblast cells in the primitive streak?

Answer 44

They displace the hypoblast cells and a trilaminar disc forms

Question 45

Which germ layer touches the amniotic cavity?

Answer 45

Ectoderm

Question 46

Which germ layer touches the yolk sac?

Answer 46

Endoderm

Question 47

What is the notochord?

Answer 47

A solid tube that sits in the mesoderm

Question 48

Where do the cells of the notochord come from and how do they get there?

Answer 48

- Ectoderm - Travel through the mesoderm and form a rod of cells in between the mesoderm and the endoderm

Question 49

What does the notochord help form?

Answer 49

Neural tube

Question 50

How does the notochord form the neural tube?

Answer 50

- Sends signals to ectoderm cells - Ectoderm thickens to form something called the neural plate

Question 51

What shape does the ectoderm take after the signals from the notochord?

Answer 51

A sine wave shape

Question 52

How does the sine wave shape of the ectoderm form the tube like structure of the neural tube?

Answer 52

The peaks of the sine wave move closer together until they touch

Question 53

What system is the neural tube the primitive structure of?

Answer 53

CNS

Question 54

How many parts does the mesoderm split into?

Answer 54

3 major parts

Question 55

What is the mesoderm part next to the neural tube (axis) known as?

Answer 55

Paraxial mesoderm

Question 56

What is the bit of the mesoderm beside the paraxial mesoderm called?

Answer 56

Intermediate mesoderm

Question 57

What is the most lateral part of the mesoderm called?

Answer 57

Lateral plate mesoderm