Session 1: Intro + Development weeks 1 & 2

Question 1

Name the parts of the female reproductive system (7)

Answer 1

Uterus
Ovaries
Fallopian Tube
Ampulla with fimbriae
Cervix - internal and external os
Vagina
Labium minus

Question 2

How many spermatozoa does one spermatocyte produce during spermatogenesis?

Answer 2

Four

Question 3

How many chromosomes and chromatids does a cell have right before meiosis I?

Answer 3

46 Chromosomes
92 Chromatids
(This is how one diploid cell produces four haploid cells)

Question 4

What happens to the primary oocyte during ovens is to form a zygote

Answer 4

It goes into meiosis arrest (Prophase I)
Prior to ovulation, it continues meiosis I and forms secondary oocyte that arrests in metaphase II
Meiosis II is completed upon fertilisation to form zygote

Question 5

Why does oogenesis produce 3 small polar bodies and one larger ovum?

Answer 5

The egg that is produced has to contain a lot of nutrients - it has survive in the uterus for 12 weeks before it gets a good blood supply from the placenta

Question 6

How do sperm navigate their way towards the ovum?

Answer 6

Thermotaxis - sperm have heat sensors

Question 7

Where exactly does fertilisation take place?

Answer 7

Ampullary region of the Fallopian tube

Question 8

How long are sperm and ovum viable in the Fallopian tube?

Answer 8

Sperm - five days

Ovum - 12-24 hours

Question 10

What role does semen/seminal fluid play in the implantation of the embryo?

Answer 10

Immunosuppressive properties

Question 11

What is embryonic age?

Answer 11

Time since fertilisation

Question 12

What is gestational age?

Answer 12

Time since last menstruation - embryonic age minus 2 weeks

Question 13

What is germinal stage?

Answer 13

Time from fertilisation to the end of the second week

Question 14

What is the embryonic period?

Answer 14

Weeks 3 to 8

Question 15

What is a morula?

Answer 15

‘Mulberry’ shaped ball of cells formed by zygote undergoing mitosis 3-4 days post-fertilisation

Question 16

What is a blastocyst?

Answer 16

Hollow ball of cells (4-5 days post-fertilisation)

Question 17

What is a zygote?

Answer 17

2-celled with zona pellucida surrounding it

Question 18

What are the roles of the zona pellucida? (2)

Answer 18

1. Stops implantation of blastocyst in the Fallopian tube (wrong place)
2. Stops morula from enlarging - cells get smaller as they divide

Question 19

In a blastocyst, what do the following develop into?

1. Outer cell mass
2. Inner cell mass
3. Cavity

Answer 19

1. Trophoblast -> yolk sac + placenta
2. Embryoblast + primitive endoderm
3. Fluid-filled bag in the uterus

Question 20

What modes of nutrition does an embryo use up to the 12th week and after 12 weeks?

Answer 20

Up to 12th week - histiotrophic nutrition (independent of maternal blood)

12th week onwards - haemotrophic nutrition (dependent on maternal blood)

Question 21

Where does implantation normally occur?

Answer 21

Posterior wall of the upper part of the body of the uterus

Question 22

What is an ectopic pregnancy? How does it occur (3)?

Answer 22

Abnormal implantation of the embryo - eg. ovary, Fallopian tube, abdominal cavity

Question 23

What is hatching?

Answer 23

Process of blastocyst losing the zona pellucida to allow implantation

Question 24

What happens to the trophoblast when it makes contact with the endometrium during implantation?

Answer 24

Differentiation into 2 layers - inner cytotrophoblast and outer syncytiotrophoblast

Question 25

What happens to the embryoblast upon implantation?

Answer 25

Differentiation - bilaminar embryonic disc (epiblast and hypoblast)

Question 26

What is the amniotic cavity?

Answer 26

Cavity formed in the epiblast after implantation - embryo resides in this throughout pregnancy

Question 27

What is the foetal period?

Answer 27

Time from start of week 9 to birth at week 40 (gestational age)

Question 28

Which cells form the primitive yolk sac?

Answer 28

Exocoelomic membrane (Migrated cells of the hypoblast covering inner wall of cytotrophoblast) + hypoblast

Question 29

How does maternal blood and hormonal secretions from glands reach the embryo?

Answer 29

TRICK QUESTION - maternal blood only comes into close proximity of the embryo - allows exchange of gases and metabolites Enzymes from the expanding syncytiotrophoblast erode lining of the maternal sinusoids and uterine glands to allow maternal blood and uterine secretions to flow into lacunar networks -> connecting stalk -> yolk sac (preliminary circulatory system)

Question 30

What is the extraembryonic mesoderm?

Answer 30

Cells between outer wall of primitive yolk sac and inner wall of cytotrophoblast

Question 31

What is the chorionic cavity?

Answer 31

Fused cavities formed from extraembryonic mesoderm

Question 32

What is the secondary yolk sac?

Answer 32

Smaller cavity remaining after pinching off large portion of primitive yolk sac (extracoelomic cavity)

Question 33

What happens in week 2 of development? (3)

Answer 33

1. Trophoblast differentiates into 2 layers - cytotrophoblast and syncytiotrophoblast 2. Embryoblast forms 2 layers - epiblast and hypoblast 3. Hypoblast contributes to the formation of 2 cavities - yolk sac and chorionic cavity

Question 34

How and when is the bilaminar embryonic disc joined to the trophoblast? What is its significance?

Answer 34

``` Connecting stalk (band of extraembryonic mesoderm) - future umbilical cord By the end of 2nd week of development ```