Pregnancy

Question 1

What is external fertilization?

Answer 1

fusion of gametes outside of the body
common in aquatic organisms
susceptible to environmental influences

Question 2

What is internal fertilization?

Answer 2

fusion of gametes inside the body
common in terrestrial organisms

Question 3

What is capacitation?

Answer 3

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

Question 4

What reaction allows the sperm to break through the surrounding zona pellucida?

Answer 4

The acrosome reaction

Question 5

What does the sperm have to push through to bind to the zona pellucida?

Answer 5

the follicular cells of the corona radiata

Question 6

What happens when the acrosome vesicle fuses with the jelly coat?

Answer 6

releases digestive enzymes which soften the glycoprotein matrix

Question 7

What happens after the sperm pushes its way through the softened jelly coat?

Answer 7

It binds to exposed docking proteins on the egg membrane

Question 8

When does the cortical reaction occur?

Answer 8

The cortical reaction occurs once a sperm has successfully penetrated an egg in order to prevent polyspermy

Question 9

What is a cortical reaction?

Answer 9

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

Question 10

What prompts the completion of meiosis II after the fusion of an egg and sperm?

Answer 10

an influx of Ca2+ into the ova

Question 11

How is a zygote formed?

Answer 11

The egg and sperm nuclei combine to form a diploid nuclei and the fertilized cell is now called a zygote

Question 12

How is a morula formed?

Answer 12

The zygote will undergo several mitotic divisions to form a solid ball of cells called a morula

Question 13

How is a blastocyst formed?

Answer 13

As the morula continues to divide, it undergoes differentiation and cavitation (cavity formation) to form a blastocyst

Question 14

What are the 3 distinct sections of a blastocyst

Answer 14

An inner cell mass
The trophoblast
The blastocoele

Question 15

What part of the blastocyst becomes an embryo?

Answer 15

The inner cell mass

Question 16

What part of the blastocyst becomes a placenta?

Answer 16

The trophoblast

Question 17

What hormones trigger the implantation of the blastocyst into the uterine wall?

Answer 17

Autocrine hormones

Question 18

What is the final stage of early embryo development?

Answer 18

the implantation of the blastocyst into the endometrial lining of the uterus

Question 19

When does the final stage of early embryo development occur?

Answer 19

~ 7 days after fertilization

Question 20

When is hCG secreted?

Answer 20

during the first 8-10 weeks of pregnancy

Question 21

Why does the placenta secrete hormones?

Answer 21

to maintain the pregnancy after the corpus luteum has degenerated

Question 22

What do chorionic villi do?

Answer 22

Chorionic villi extend into the pools of maternal blood and mediate the exchange of materials between the fetus and the mother

Question 23

What moves across the placental membrane from mother to fetus?

Answer 23

Oxygen
Antibodies - cross the placenta via endocytosis
Water
Glucose

Question 24

What moves across the placental membrane from fetus to mother?

Answer 24

Carbon dioxide
Water
Urea