Fertilisation, Cleavage and Implantation

Question 1

What stage is the oocyte in when it is ovulated?

Answer 1

Metaphase of the second meiotic division

Question 2

What surrounds the oocyte during ovulation?

Answer 2

Zona pellucida and some granulosa cells

Question 3

How does the oocyte get from the ovary to the oviduct of the fallopian tube?

Answer 3

Fimbriae sweep the oocyte into the oviduct.

Question 4

How does the oocyte move from the oviduct to the ampulla?

Answer 4

Peristaltic waves

Question 5

How long does it take from the ovary to implantation in the uterus?

Answer 5

80 Hours

Question 6

Draw an oocyte

Answer 6

in notes

Question 7

Draw a spermatozoa

Answer 7

in notes

Question 8

What is the role of the acrosome?

Answer 8

Helps penetrate the zona pellucida by releasing enzymes

Question 9

What are the barriers to the sperm fertilising the egg?

Answer 9

Vaginal pH, Response of immune system, Cervical mucous and physical barriers e.g. condoms

Question 10

What is fertilisation?

Answer 10

The process by which the male and female zygotes fuse

Question 11

On average how long do spermatozoa retain their function in the female body?

Answer 11

72 hours

Question 12

Where does fertilisation occur?

Answer 12

In the fallopian tube within 24 hours of ovulation

Question 13

What is capacitation?

Answer 13

A 7 hour process where a glycoprotein coat and seminal plasma proteins are removed from the spermatozoa head

Question 14

Why is capacitation important?

Answer 14

Only capacitated sperm can pass through corona cell and undergo acrosome reaction

Question 15

Describe stage 1 of fertilization

Answer 15

Penetration of corona radiata. Capacitated cells pass straight through.

Question 16

Describe stage 2 of fertilization

Answer 16

Penetration of zona pellucida.

Question 17

What is the zona pellucida made up of?

Answer 17

Glycoproteins

Question 18

What is the function of the zona pellucida?

Answer 18

Facilitates and maintains cell binding + induces the acrosome reaction

Question 19

Describe stage 3 of fertilization

Answer 19

Cortical and Zona reactions. Cortical granules release hydrolytic enzymes which cleaves ZP2 and modifies ZP3 which means no more sperm can bind

Question 20

What is important about cortical granules

Answer 20

They release hydrolytic enzymes which prevents polyspermy

Question 21

Describe stage 4 of fertilization

Answer 21

Fusion of membranes and resumption of 2nd meiotic division - head and tail of sperm enter but plasma membrane left behind.

Question 22

Describe oogenesis and follicle development

Answer 22

In notes just look at them

Question 23

Describe stage 5 of fertilization

Answer 23

Formation of male and female pronuclei. They contain 23 chromosomes each. The membranes break down and the chromosomes are arranged for mitosis

Question 24

What is cleavage

Answer 24

A series of mitotic divisions.

Question 25

Describe cleavage

Answer 25

The blastomere divides until it is a 16 cell morula which undergoes compaction to become a blastocyst

Question 26

What is implanted into the uterus?

Answer 26

The blastocyst

Question 27

Label the blastocyst

Answer 27

in notes

Question 28

What does the outer cell mass of the blastocyst become?

Answer 28

The trophoblast

Question 29

What phase of menstruation are females in at the time of implantation?

Answer 29

Secretory

Question 30

Where does the blastocyst implant?

Answer 30

The endometrium

Question 31

What are the stages of menstruation?

Answer 31

Menstruation, proliferation, secretion, implantation window (would be menstruation if no fertilisation occurs)

Question 32

What does the trophoblast differentiate into?

Answer 32

Syncytiotrophoblast and Cytotrophoblast

Question 33

What happens to the uterine mucosa?

Answer 33

It reacts to the implantation by the decidual reaction. The ST phagocytose the decidual cells and erode capillaries.

Question 34

What does the ST do?

Answer 34

It produces lytic acid and secretes factors that cause apoptosis of endometrial epithelial cells.

Question 35

What happens in the middle of week 2

Answer 35

Lacunae appear in ST, which fill with blood. The ST stops in the zona compacta

Question 36

What happens on day 13

Answer 36

Primitive uteroplacental circulatory system arises

Question 37

Which way round are the amniotic cavity and umbilical vesicle?

Answer 37

Amniotic cavity - Dorsal and umbilical vesicle - Ventral.

Question 38

What forms the floor of the amniotic cavity and roof of the umbilical vesicle

Answer 38

The epiblast - Floor, Hypoblast - roof

Question 39

What are 3 parent babies for?

Answer 39

Mitochondrial diseases

Question 40

What does a 3 parent baby mean?

Answer 40

Genes of parent are inserted into the egg of the donor, the the donors are removes but the functional mitochondria is left.