Pregnancy Flashcards
What is external fertilization?
fusion of gametes outside of the body
common in aquatic organisms
susceptible to environmental influences
What is internal fertilization?
fusion of gametes inside the body
common in terrestrial organisms
What is capacitation?
Capacitation occurs after ejaculation, when chemicals released by the uterus dissolve the sperm’s cholesterol coat
It also destabilizes the acrosome cap, which is necessary for the acrosome reaction to occur upon egg and sperm contact
What reaction allows the sperm to break through the surrounding zona pellucida?
The acrosome reaction
What does the sperm have to push through to bind to the zona pellucida?
the follicular cells of the corona radiata
What happens when the acrosome vesicle fuses with the jelly coat?
releases digestive enzymes which soften the glycoprotein matrix
What happens after the sperm pushes its way through the softened jelly coat?
It binds to exposed docking proteins on the egg membrane
When does the cortical reaction occur?
The cortical reaction occurs once a sperm has successfully penetrated an egg in order to prevent polyspermy
What is a cortical reaction?
Cortical granules within the egg’s cytoplasm release enzymes into the zona pellucida
These enzymes destroy sperm binding sites and also thicken and harden the glycoprotein matrix of the jelly coat
This prevents other sperm from being able to penetrate the egg, ensuring the zygote formed is diploid
What prompts the completion of meiosis II after the fusion of an egg and sperm?
an influx of Ca2+ into the ova
How is a zygote formed?
The egg and sperm nuclei combine to form a diploid nuclei and the fertilized cell is now called a zygote
How is a morula formed?
The zygote will undergo several mitotic divisions to form a solid ball of cells called a morula
How is a blastocyst formed?
As the morula continues to divide, it undergoes differentiation and cavitation (cavity formation) to form a blastocyst
What are the 3 distinct sections of a blastocyst
An inner cell mass
The trophoblast
The blastocoele
What part of the blastocyst becomes an embryo?
The inner cell mass
What part of the blastocyst becomes a placenta?
The trophoblast
What hormones trigger the implantation of the blastocyst into the uterine wall?
Autocrine hormones
What is the final stage of early embryo development?
the implantation of the blastocyst into the endometrial lining of the uterus
When does the final stage of early embryo development occur?
~ 7 days after fertilization
When is hCG secreted?
during the first 8-10 weeks of pregnancy
Why does the placenta secrete hormones?
to maintain the pregnancy after the corpus luteum has degenerated
What do chorionic villi do?
Chorionic villi extend into the pools of maternal blood and mediate the exchange of materials between the fetus and the mother
What moves across the placental membrane from mother to fetus?
Oxygen
Antibodies - cross the placenta via endocytosis
Water
Glucose
What moves across the placental membrane from fetus to mother?
Carbon dioxide
Water
Urea
