Embryology 1 Flashcards
Development of the Human (4 Phases)
- Pre-embryonic phase 0-3 weeks
- Embryonic phase 4-8
- Foetal phase 9-40 weeks
- Postnatel/childhood/adolescent…
Describe the process of oogenesis
Oogonium (46 chromosomes) divides to form primary oocyte
Primary oocyte goes through meiosis to form an ovum (22+X) and 3 polar bodies
Spermatogenesis
Spermatogonium (46 chromosomes) divides to become primary spermatocyte
Primary spermatocyte goes through meiosis I to form two secondary spermatocytes
Secondary spermatocytes go through meiosis II to form 4 sperm cells (22+X or 22+Y chromosomes)
Describe the process of fertilisation
Several sperm surround the ovum and only one penetrates
Pro nucleus of sperm enters and fuses with the pro nucleus of ovum
This gives a diploid cell called the ZYGOTE
What happens during week 1 of the Pre-embryonic phase?
Zygote (diploid) divides by mitosis and forms a solid ball of cells called MORULA
As the size increases of the morula the central core of it struggles for nutrients so a blastocystic cavity develops.
The cells accumulate at one end of the blastocyst to form inner cell mass.
The outer lining is called the trophoblast.
What happens to the time it takes for cells division from the first one to the successive one.
Cell division takes lesser and lesser time from the 1st one to the successive ones.
How does the zygote travel from the fallopian tube tot he utreine cavity?
Healthy ciliated epithelium in the fallopian tube allow the dividing zygote/ morula/ blastocysts to move to the uterine cavity where the blastocyst is implanted.
Describe what happens to the trophoblast at week 2
The trophoblast that originally is the outer cell mass divides to form two layers called the CHORION.
Also develops finger like projections called the chrionic villi.
What happens to the inner cells mass of the blastocyst at week 2?
Inner cell mass form a 2-layer flat bilaminar disc (epiblast and hypoblast), forming 2 cavities: Amniotic cavity and Yolk sac.
What are the functions of the chorion? (3)
Implantation process (chorionic villi)
Forms part of the placenta in due course
Secretes human Chorionic gonadotropin (HCG) (used to detect pregnancy)
What does the HCG maintain?
hCG (Human Chorionic Gondaptropin) secreted by the chorion helps maintain the endometrium
What is the decidua basalis?
Decidua basalis is the area of the endometrium between the implanted chorionic sac and the myometrium.
When might an ectopic pregnancy occur?
If the cilia function is lost
Where and when does implantation of the blastocyst occur?
Implantation occurs in the uterine endometrium
At day 7 the blastocyst begins to burrow into the uterine wall (endometrium)
Why are mitochondrial diseases inherited by the mother?
Mitochondria and other cell organelles in the zygote is from the mother, therefore any mitochondrial diseases are inherited from the mother.
