2B - Human Reproduction Flashcards
Fertilization, Embryonic, and Fetal Development
What is fertilization?
The process where a sperm cell fuses with an egg cell to form a zygote (a single-cell embryo).
Where does fertilization occur?
In the oviduct/ the fallopian tube.
What happens after the sperm enters the egg?
The sperm and egg nuclei fuse, forming a zygote (a single diploid cell with 46 chromosomes).
What is cleavage?
Rapid mitotic divisions of the zygote, creating smaller cells without increasing overall size.
2-cell stage -> 4-cell stage -> 8-cell stage -> 16-cell stage (morula)
What is the morula?
A solid ball of 16–32 cells formed by cleavage, before becoming a blastocyst.
What is the blastocyst?
A hollow structure that forms from the morula. It has an inner cell mass (embryoblast) and an outer layer (trophoblast).
What does the trophoblast do?
It helps the blastocyst implant into the uterus and later forms the placenta.
What is the embryoblast and what does it become?
The embryoblast is the inner cell mass of the blastocyst. It develops into the embryo and later forms the baby
What is Blastulation?
Blastulation is the process where the morula (a solid ball of cells) transforms into a blastocyst (a hollow structure with an inner cell mass). This happens around days 4–5 after fertilization.
What is gastrulation?
Gastrulation is the process where the blastula (blastocyst in mammals) transforms into a three-layered embryo by forming the three germ layers.
When does gastrulation occur?
Around week 3 of embryonic development.
What structure initiates gastrulation?
The primitive streak, a groove on the surface of the epiblast where cells migrate inward.
What are the three germ layers formed during gastrulation?
Ectoderm → Becomes skin, nervous system,
Mesoderm → Becomes muscles, bones,
Endoderm → Becomes digestive system lining and lungs lining
Why is gastrulation important?
It establishes the basic body plan and determines which cells will develop into specific tissues and organs.
What is the notochord and what does it do?
A rod-like structure from the mesoderm that signals the development of the nervous system.
What is the yolk sac and what is its function?
The yolk sac is like a “starter kit” for the embryo.
It provides early nutrients before the placenta is fully developed, much like a starter kit helps begin a project.
Makes RBC’s and forms parts of your digestive system. lined w endoderm
What is the amniotic cavity and what is its function?
The amniotic cavity is like a “water bed”.
It cushions and protects the embryo from physical shock and helps maintain a stable environment with amniotic fluid, much like a water bed supports and cushions your body.
What is the amnion and what is its function?
The amnion is like a “protective plastic wrap”.
It wraps around the embryo, holding in the amniotic fluid and keeping the embryo protected, much like plastic wrap holds food securely in place.
What is the endometrium and what is its function?
The endometrium is like a “welcome mat”.
It prepares the uterine lining for the embryo to attach and settle in, just like a welcome mat prepares your home for guests.
What is the embryo and what is its function?
The embryo is like a “blueprint”.
It is the early developmental stage that defines the future body and will eventually form the baby, just like a blueprint defines the structure of a house.
What is the allantois and what is its function?
The allantois is like the “garbage disposal” in your kitchen.
It helps dispose of the waste produced by the embryo before the placenta takes over that role, similar to how a garbage disposal gets rid of food waste.
Associated with the formation of the umbilical cord.
What is the chorion and chorionic villi and what is their function?
The chorion and chorionic villi are like the “roots of a tree”.
The chorion is the trunk, and the chorionic villi are the roots that anchor the placenta into the uterine wall, providing nutrients to the embryo, just like roots anchor a tree and supply nutrients.
What is the maternal blood pool and what is its function?
The maternal blood pool is like a “river” flowing near a “water mill”.
The river (maternal blood) brings oxygen and nutrients, which flow into the “water mill” (chorionic villi) to power the baby’s growth and filter out waste, similar to how a river powers a water mill.
What are the 4 extra embryonic structures that support the embryo that came from the trophoblast?
Yolk sac, amnion, allantolis, chorion
