Early Human Development (Questions)

Question 1

What is a zygote, and where does it form?

Answer 1

A zygote is a diploid, single-cell organism that forms in the uterine tube after fertilization.

Question 2

What process does the zygote undergo after formation?

Answer 2

The zygote undergoes 4-5 mitotic divisions called cleavage divisions, forming a morula.

Question 3

What is a morula, and how many cells does it consist of?

Answer 3

A morula is a solid ball of 16-32 cells, and it is the same size as the ovum/zygote.

Question 4

At what stage do cells start to differentiate into specific cell types?

Answer 4

Cells begin to differentiate during the morula stage and continue to do so as the blastocyst forms.

Question 5

What is a blastocyst, and what key features does it have?

Answer 5

A blastocyst is a stage of embryonic development featuring a fluid-filled cavity (blastocoel), an embryoblast (inner cell mass), and a trophoblast.

Question 6

What is the function of the embryoblast in the blastocyst?

Answer 6

The embryoblast will later divide and differentiate to form the embryo.

Question 7

What does the trophoblast in the blastocyst develop into, and what is its function?

Answer 7

The trophoblast develops into the chorion, which provides nutrients to the developing embryo.

Question 8

What happens during implantation?

Answer 8

The blastocyst moves from the uterine tube and attaches to the endometrium of the uterine wall, marking the process of implantation.

Question 9

After implantation, what does the embryoblast differentiate into?

Answer 9

The embryoblast differentiates into a bilayered embryonic disc, consisting of the epiblast and hypoblast.

Question 10

What will the epiblast form through mitosis?

Answer 10

The epiblast will form the amnion with a fluid-filled amniotic cavity and the three germ layers of the embryo.

Question 11

What will the hypoblast form through mitosis?

Answer 11

The hypoblast will form the yolk sac.

Question 12

What structures begin to form alongside the embryonic disc?

Answer 12

Extraembryonic membranes begin to form to support the developing embryo.

Question 13

What period does the embryonic stage cover?

Answer 13

The embryonic period covers from the 3rd week to the end of the 8th week.

Question 14

What are the three germ layers formed during the embryonic period?

Answer 14

The three germ layers are the ectoderm, mesoderm, and endoderm.

Question 15

What does the ectoderm form?

Answer 15

The ectoderm forms the nervous system and the epidermis of the skin.

Question 16

What does the mesoderm form?

Answer 16

The mesoderm forms muscles, the cardiovascular system, the dermis, and most bones.

Question 17

What does the endoderm form?

Answer 17

The endoderm forms the epithelial linings of the digestive, respiratory, urinary, and reproductive systems, as well as their associated glands.

Question 18

What major developments occur during the embryonic period?

Answer 18

During this period, major organ systems are almost completely formed, the heart begins to beat, and limb buds differentiate.

Question 19

What extraembryonic membrane is derived from trophoblast cells?

Answer 19

The chorion is derived from trophoblast cells.

Question 20

What is the function of chorionic villi?

Answer 20

Chorionic villi contain blood vessels and form the fetal part of the placenta, facilitating nutrient, waste, and gas exchange between fetal and maternal blood.

Question 21

What extraembryonic membrane forms the amniotic cavity, and what is the function of amniotic fluid?

Answer 21

The amnion, derived from the epiblast, forms the amniotic cavity. Amniotic fluid provides shock absorption and temperature regulation for the embryo/fetus.

Question 22

What does the yolk sac form, and what is its role in early development?

Answer 22

The yolk sac forms part of the digestive tract and is a source of reproductive germ cells and embryonic blood cells.

Question 23

What is the allantois, and what does it develop into?

Answer 23

The allantois is a projection off the yolk sac that forms the umbilical cord and the urinary bladder.

Question 24

What period follows the embryonic period, and what occurs during this time?

Answer 24

The fetal period follows, starting in the 9th week and lasting until the end of the 40th week, during which organ growth and maturation occur.