Embryology Flashcards
At which weeks in the pre-embryonic phase?
Weeks 0-3
At which weeks is the embryonic phase?
Weeks 4-8
At which weeks is the foetal phase?
Weeks 9-40
What three stages come after the birth of a child?
Postnatal, childhood, adolescence.
At the end of which week are all the building blocks for the different systems made?
By the end of week 8
What happens to the building blocks after week 8?
They get developed into systems/ organs etc.
Name the cell in which sperm comes from.
Spermatogonium
Name the cell in which ova come from.
Oogonium
When hitting adolescence, how many sperm cells are formed from the meiosis of spermatogonium?
4
What does one oogonium divide into?
1 ovum and 3 polar bodies.
How many sperm surrounds the ova?
Hundreds
How many sperm penetrates the ova?
1
How mcuh of the sperm cell actually enters the ova?
Only the genetic material, everything else is left outside.
What is produced when the ova and sperm fuse?
Zygote
What is the process of the production of a zygote known as?
Fertilisation.
What does the zygote divide to form?
Blastocyst.
What is the first cell in the body?
Zygote
How many chromosomes in a diploid zygote?
46
Where does the foetus get the mitochondria, cellular organelles etc from?
The mother
What is a morula?
Clump of cells in the early embryo
The zygote divides through mitosis to eventually form what?
Morula
If a women has mitochondrial diseases, what are the chances she passes these on to her children?
100%
If a man has mitochondrial diseases, what are the chances she passes these on to her children?
0%
As the number and size of cells in the morula increases, what is one problem?
Difficult to get nutrition to cells in the centre core
What cavity can form in morula when there are too many large cells?
Blastocyst cavity
If cells accumulate at one end of the blastocyst, what is this known as?
Inner cell mass
What are trophoblasts?
Cells which form the outer layer of a blastocyst.
Briefly describe the reproduction system.
Composed of uterus, fallopian tubes/ uterine tubes and ovary.
Ovary is close to finger like processes but not attached.
One ovum released every month and it captured by uterine tube and travels along the fallopian tubes.
How does the dividing zygote move through the fallopian tube?
Cillia
Why may an ectopic pregnancy occur?
If cillia function is abnormal
Why may an ectopic pregnancy occur?
If cilia function is abnormal
Where does implantation occur?
In the uterine edometrial layer.
What happens in week 2 of the pre-embryonic phase?
-Implantation occurs
-Placenta starts to develop
-Cells from bilaminar disc
-Sac, membranes and cord start to form to nourish the baby
When is the tropholast formed?
About day 5
Finger like processes=?
Villi
How is the chorion formed?
Trophoblast divides to form two layers
What does chorion do?
- Implantation process
- Forms part of the placenta
- Secretes human chorionic gonadotropin (HCG)
What is HCG used for?
Detecting pregnancy
What does the blastocyst do on day 7?
Begins to bury into the uterine wall (endometrium) assisted by the chorion.
Maternal blood and urine levels of HCG increase until?
12 weeks gestation
What happens to the inner cell mass?
Form bilaminar disc and amniotic cavity and yolk sac begin to form
What happens as the yolk sac increases?
Allatoic cavity increases with waste material/
Which cavity surrounds the embryo?
Amniotic cavity
Name the four cavities in a human embryo
Amniotic cavity- AC
Chorionic cavity- CC
Allantoic cavity- AL
Yolk sac- YS
What are the three main functions of the placenta?
- Foetal nutrition
- Transport of waste and gases
- Immunity
Describe the foetal part and surface of the placenta
Smooth with foetal blood vessels and the end of the umbilical cord.
When does the placenta mature by?
18-20 weeks
What proportion of the foetus does the placenta weigh?
1/6
What is the maternal part of the placenta?
Decidua basalis of endometrium
Describe the decidua basalis of the endometrium.
Rough and has maternal blood vessels.
Describe how fraternal/dizygotic twins come about.
2 ova released + 2 sperm + two separate zygote
Different genetic makeup and 2 placenta.
Can run in families.
Describe how identical/ monozygotic twins come about.
1 ova + 1 sperm = 1 zygote
Zygote divides into two and each cell develops into a different embryo
Same genetic makeup as share the same placenta
Give a summary of weeks 1 & 2 of embryology :)
Fertilisation ->zygote
Zygote-> morula which reaches uterine cavity.
Blastocyst implants.
Outer cells form chorionic villi which assist with implantation.
Decidua basalis forms and placental formation begins.
