Embryology 1 Flashcards
What are the three phases of pregnancy?
What are the cells that produce the sperm cells and the ova?
Spermatogonia Oogonia
Where are the Spermatogonium Oogonium found?
Gonads
What is the contents of a sperm cell?
22 chromosomes, 1 X, or 1 Y
What is the contents of an ovum?
(22+X) and 3 polar bodies
What fuses to from the zygote?
(pro)Nucleus of sperm enters and fuses with the (pro)nucleus of ovum to give a diploid cell called the ZYGOTE
What part of the sperm enters the ovum?
Only the nucleus. The rest of the cell is left behind
What happens during week one of pre-embryonic phase?
Why are zygotes always unique?
No two sperm/ova are the same
Which parent is mitochondrial disease inherited from?
Mother
What is a solid ball of cells formed from a zygote called?
A morula
What day is a blastocyst formed?
Day 5/6 of pre-embryonic phase
Why is the blastocystic cavity formed?
•As the number (and size) of cells increase, getting nutrition to the central core of cells starts becoming difficult
How is the blastocystic cavity formed?
- Cells accumulate at one end to form an inner cell mass.
- The outer lining of cells is called the trophoblast.
How long does the first cell division take?
36 hours
What happens on day 5/6?
The blastula has formed and this has reached the uterine cavity ready to implant in it.
What is required for the the dividing zygote/ morula/ blastocyst fallopian tube to move and reach the uterine cavity?
requires healthy ciliated epithelium
When is ectopic pregnancy likely to occur?
Could occur if cilia function is abnormal, pregnancy occurs in the uterine tube. Complications inculde rupturing of the uterine tubes.
What is the endometrium?
The mucous membrane lining the uterus, which thickens during the menstrual cycle in preparation for possible implantation of an embryo.
When does the placenta start to develop?
This may start by day 6 of 1st week, when implantation occurs in the uterine endometrial layer
What is the structure called that ater forms the embryo?
Bilaminar disc
What structures do we see start to form at week 2?
•Sacs, membranes and cord to nourish the human conceptus (baby) start to form
What is the role of the chorion?
Burrowing
What cells are initially called to trophoblasts?
Cells that form the outer cell mass
What forms the chorion?
The trophoblast
What does the chorion form?
Finger like processes (chorionic villi)
What does the Chorion do?
What is the function of HCG?
Tells the ovary to continue producing oestrogen and progesterone, so that the endometrium does not get shed.
What is used to test for pregnancy?
HCG
What is the decidua basalis?
part of the endometrium deep to the implanted conceptus.
What is the decidua?
The are in the endometrium where the blastocyst implants
Which part of the endometrium contains more blood vessels?
Decidua basalis
When does HCG content increase until?
•Maternal blood (and urine) levels of hCG increase till around 12 weeks gestation
What is the change in structure of the inner cell mass?
•The cells of the inner cell mass form a 2–layered flat disc called the BILAMINAR DISC
What is the name of the two cell cavities formed by the inner cell mass?
- 2 cavities now begin to form:
- Amniotic cavity (A)
- Yolk sac (Y)
What is the name of the abbreviated structures?
How does the chorion handle the blood of the embryo?
Prevents maternal blood and embryo blood to mix?
Look
What are the main functions of the placenta?
Main functions:
- Foetal nutrition
- Transport of waste and gases
- Immune etc
Which part of the placenta is smooth?
Foetal part and surface: smooth with foetal blood vessels and end of umbilical cord
Which part of the placenta is rough?
Maternal part: Decidua basalis of endometrium
Rough and has maternal blood vessels
When is the placenta mature?
By 18-20 weeks
How are fraternal/dizygotic twins formed?
How does an identical twin/monozygotic twin formed?
Summary of Weeks 1 and 2
