Embryology Flashcards
When does meiosis 1 of the oogonium occur?
During foetal stage
When does meiosis 2 occur?
Adolescence
What does fertilisation produce?
A zygote
What is the process of fertilisation?
100s of sperm surround the egg (ovum) but only 1 will penetrate
(pro) nucleus of the sperm enters and fuses with the (pro) nucleus of ovum to give a diploid cell (zygote)
What happens in week one (pre-embryonic phase)?
Zygote divides to form a blastocyst.
Moves through uterine tube to reach uterine cavity.
What does a zygote develop into next?
Morula via mitosis
What is a morula?
A solid ball of cells
What does a morula develop into next and why?
Blastocyte
Due to being a solid mass of cells, central cells cannot get enough nutrients from diffusion so cell reforms.
Forms a blastocystic cavity where cells accumulate at one end to form an inner cell mass and an outer lining of cells called the trophoblast.
What are the parts of a blastocyte?
Trophoblast
Inner cell mass
Blastocyte cavity
When does implantation occur and what starts to form?
Day 6
Placenta begins to develop
- sacs, membranes and cord to nourish the human conceptus (baby) start to form.
What is formed after a blastocyst?
Trophoblast
What does a trophoblast develop into next and how?
Continues to divide and develop finger like processes called chronic villi
Chorion
What does a chorion do?
Implants into the uterine wall
- Finger like processes help it bury into the uterine wall
Forms part of the placenta (eventually)
Secretes HCG hormone
What does the HCG hormone show?
Excreted in urine and used to detect pregnancy
The hormone stops the endometrium from shedding every month
What happens to the inner cell mass in the chorion?
Flattens itself to form a bilaminar disc
2 layers:
- Epiblast
- Hypoblast
2 cavities:
- Amniotic cavity
- Yolk sac
