Early Embryology 1 and 2 Flashcards
The main stages of embryology include:
Fertilization – Fusion of sperm and egg to form a zygote.
Cleavage – The zygote undergoes rapid cell divisions to form a morula.
Blastulation – Formation of the blastocyst from the morula, with the development of a blastocyst cavity.
Gastrulation – Formation of the three germ layers (ectoderm, mesoderm, and endoderm).
Neurulation – Formation of the neural tube, which gives rise to the central nervous system.
Organogenesis – Development of organs and structures from the three germ layers.
What is the formation of gametes and fertilization?
Formation of gametes:
Oogenesis (formation of eggs in females) occurs in the ovaries, where primordial germ cells undergo meiosis to produce a haploid ovum.
Spermatogenesis (formation of sperm in males) occurs in the testes, where spermatogonia undergo meiosis to produce haploid sperm.
Fertilization:
Fertilization occurs when a sperm cell penetrates an egg cell, combining their genetic material to form a zygote with a diploid set of chromosomes (one from each parent).
What is the formation of the blastocyst and its implantation into the uterine wall?
After fertilization, the zygote undergoes cleavage to form a morula (a solid ball of cells).
The morula forms a blastocyst, which has an inner cell mass (embryoblast), a trophoblast (outer layer), and a blastocyst cavity.
The blastocyst then travels down the fallopian tube into the uterus, where the trophoblast cells implant into the endometrium (uterine wall), initiating pregnancy.
What is the formation of the placenta, placental villi, and its functions?
The placenta forms from the trophoblast cells of the blastocyst and the maternal endometrial tissue.
The placental villi are finger-like projections of trophoblast cells that extend into the uterine wall, facilitating exchange of nutrients, gases, and waste products between the maternal and fetal blood.
Functions of the placenta include:
Nutrient and gas exchange (oxygen, carbon dioxide)
Hormone production (e.g., hCG, progesterone) to maintain pregnancy
Protection (barrier against some infections and toxins)
What is the formation of the bilaminar disc?
The bilaminar disc forms during the second week of embryonic development.
It consists of two layers:
Epiblast (the upper layer that gives rise to the embryo)
Hypoblast (the lower layer that contributes to the formation of extra-embryonic tissues).
These two layers form the early embryonic structure, providing the foundation for further development.
What is the formation of the trilaminar disc?
The trilaminar disc forms during gastrulation in the third week of embryonic development.
The three germ layers are:
- Ectoderm (gives rise to the nervous system, skin, and other structures)
- Mesoderm (forms muscles, bones, cardiovascular system, etc.)
- Endoderm (forms the gut, lungs, and other internal organs).
This three-layered structure marks a critical step in the formation of the body plan and organ systems.
