fertilisation and stages of prenatal development Flashcards
fertilisation def
the fuse of a sperm and egg cell. Marks the beginning of pregnancy. Also known as conception.
general info on fertilisation
- intercourse finish
sperm make way to vagina (toward fallopian tube) - if ovum present, per will attempt to break through membrane cell
- no other sperm can enter
- Fuses DNA –> Zygote
Germinal stages (0-2 years)
the germinal stage starts at fertilisation and ends with implantation. when fertilised, the newly formed cell (zygote) travels down the fallopian tubes and keeps dividing
characteristics of germinal stage
1 day after fertilisation
- new zygote divides as it travels down the fallopian tubes
4 days after fertilisation
- zygote contains around 6 cells (now called MORULA )
5 days after fertilisation
- morula now has 64 cells and turns into a BLASTOCYST
-inner mass will become empbryo and outer becomes placenta
7-12 days after fertilisation
- reacts uterus, the blastocyst implants itself into the endometrium and becomes an EMBRYO
embryonic stage (3-8 weeks)
This stage is characterised by cell differentiation. When cells start taking on specialised roles such as :
heart
skin
cell
bones etc
more critical stage
characteristics of embryonic stage
-from implantation until end of week 8
-internal and external organs and systems are formed
- TERATOGENS are risk factors during this phase (drugs, alcohol, meds0
foetal stage (9 - 38 weeks )
foetal stage starts at the ninth week of pregnancy and continues until birth at around 38 weeks. During this stage, the unborn baby is referred to as a foetus.
characteristics of foetal stage
-longest prenatal stage
- this period is a time of a massive growth (organs)
- all nerves and muscles and organs begin to function. ( Lungs, Hiccups, kidneys, liver)
- placenta is formed and functions during this phase
