Fertilisation, Cleavage and Implantation Flashcards
What stage is the oocyte in when it is ovulated?
Metaphase of the second meiotic division
What surrounds the oocyte during ovulation?
Zona pellucida and some granulosa cells
How does the oocyte get from the ovary to the oviduct of the fallopian tube?
Fimbriae sweep the oocyte into the oviduct.
How does the oocyte move from the oviduct to the ampulla?
Peristaltic waves
How long does it take from the ovary to implantation in the uterus?
80 Hours
Draw an oocyte
in notes
Draw a spermatozoa
in notes
What is the role of the acrosome?
Helps penetrate the zona pellucida by releasing enzymes
What are the barriers to the sperm fertilising the egg?
Vaginal pH, Response of immune system, Cervical mucous and physical barriers e.g. condoms
What is fertilisation?
The process by which the male and female zygotes fuse
On average how long do spermatozoa retain their function in the female body?
72 hours
Where does fertilisation occur?
In the fallopian tube within 24 hours of ovulation
What is capacitation?
A 7 hour process where a glycoprotein coat and seminal plasma proteins are removed from the spermatozoa head
Why is capacitation important?
Only capacitated sperm can pass through corona cell and undergo acrosome reaction
Describe stage 1 of fertilization
Penetration of corona radiata. Capacitated cells pass straight through.
Describe stage 2 of fertilization
Penetration of zona pellucida.
What is the zona pellucida made up of?
Glycoproteins
What is the function of the zona pellucida?
Facilitates and maintains cell binding + induces the acrosome reaction
Describe stage 3 of fertilization
Cortical and Zona reactions. Cortical granules release hydrolytic enzymes which cleaves ZP2 and modifies ZP3 which means no more sperm can bind
What is important about cortical granules
They release hydrolytic enzymes which prevents polyspermy
Describe stage 4 of fertilization
Fusion of membranes and resumption of 2nd meiotic division - head and tail of sperm enter but plasma membrane left behind.
Describe oogenesis and follicle development
In notes just look at them
Describe stage 5 of fertilization
Formation of male and female pronuclei. They contain 23 chromosomes each. The membranes break down and the chromosomes are arranged for mitosis
What is cleavage
A series of mitotic divisions.
Describe cleavage
The blastomere divides until it is a 16 cell morula which undergoes compaction to become a blastocyst
What is implanted into the uterus?
The blastocyst
Label the blastocyst
in notes
What does the outer cell mass of the blastocyst become?
The trophoblast
What phase of menstruation are females in at the time of implantation?
Secretory
Where does the blastocyst implant?
The endometrium
What are the stages of menstruation?
Menstruation, proliferation, secretion, implantation window (would be menstruation if no fertilisation occurs)
What does the trophoblast differentiate into?
Syncytiotrophoblast and Cytotrophoblast
What happens to the uterine mucosa?
It reacts to the implantation by the decidual reaction. The ST phagocytose the decidual cells and erode capillaries.
What does the ST do?
It produces lytic acid and secretes factors that cause apoptosis of endometrial epithelial cells.
What happens in the middle of week 2
Lacunae appear in ST, which fill with blood. The ST stops in the zona compacta
What happens on day 13
Primitive uteroplacental circulatory system arises
Which way round are the amniotic cavity and umbilical vesicle?
Amniotic cavity - Dorsal and umbilical vesicle - Ventral.
What forms the floor of the amniotic cavity and roof of the umbilical vesicle
The epiblast - Floor, Hypoblast - roof
What are 3 parent babies for?
Mitochondrial diseases
What does a 3 parent baby mean?
Genes of parent are inserted into the egg of the donor, the the donors are removes but the functional mitochondria is left.
