Early Human Development (Questions) Flashcards
What is a zygote, and where does it form?
A zygote is a diploid, single-cell organism that forms in the uterine tube after fertilization.
What process does the zygote undergo after formation?
The zygote undergoes 4-5 mitotic divisions called cleavage divisions, forming a morula.
What is a morula, and how many cells does it consist of?
A morula is a solid ball of 16-32 cells, and it is the same size as the ovum/zygote.
At what stage do cells start to differentiate into specific cell types?
Cells begin to differentiate during the morula stage and continue to do so as the blastocyst forms.
What is a blastocyst, and what key features does it have?
A blastocyst is a stage of embryonic development featuring a fluid-filled cavity (blastocoel), an embryoblast (inner cell mass), and a trophoblast.
What is the function of the embryoblast in the blastocyst?
The embryoblast will later divide and differentiate to form the embryo.
What does the trophoblast in the blastocyst develop into, and what is its function?
The trophoblast develops into the chorion, which provides nutrients to the developing embryo.
What happens during implantation?
The blastocyst moves from the uterine tube and attaches to the endometrium of the uterine wall, marking the process of implantation.
After implantation, what does the embryoblast differentiate into?
The embryoblast differentiates into a bilayered embryonic disc, consisting of the epiblast and hypoblast.
What will the epiblast form through mitosis?
The epiblast will form the amnion with a fluid-filled amniotic cavity and the three germ layers of the embryo.
What will the hypoblast form through mitosis?
The hypoblast will form the yolk sac.
What structures begin to form alongside the embryonic disc?
Extraembryonic membranes begin to form to support the developing embryo.
What period does the embryonic stage cover?
The embryonic period covers from the 3rd week to the end of the 8th week.
What are the three germ layers formed during the embryonic period?
The three germ layers are the ectoderm, mesoderm, and endoderm.
What does the ectoderm form?
The ectoderm forms the nervous system and the epidermis of the skin.
What does the mesoderm form?
The mesoderm forms muscles, the cardiovascular system, the dermis, and most bones.
What does the endoderm form?
The endoderm forms the epithelial linings of the digestive, respiratory, urinary, and reproductive systems, as well as their associated glands.
What major developments occur during the embryonic period?
During this period, major organ systems are almost completely formed, the heart begins to beat, and limb buds differentiate.
What extraembryonic membrane is derived from trophoblast cells?
The chorion is derived from trophoblast cells.
What is the function of chorionic villi?
Chorionic villi contain blood vessels and form the fetal part of the placenta, facilitating nutrient, waste, and gas exchange between fetal and maternal blood.
What extraembryonic membrane forms the amniotic cavity, and what is the function of amniotic fluid?
The amnion, derived from the epiblast, forms the amniotic cavity. Amniotic fluid provides shock absorption and temperature regulation for the embryo/fetus.
What does the yolk sac form, and what is its role in early development?
The yolk sac forms part of the digestive tract and is a source of reproductive germ cells and embryonic blood cells.
What is the allantois, and what does it develop into?
The allantois is a projection off the yolk sac that forms the umbilical cord and the urinary bladder.
What period follows the embryonic period, and what occurs during this time?
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.
