Unit 3.1: Prenatal development Flashcards
What can you divide pregnancy into?
three trimester periods
Do the trimesters of pregnancy correspond with the three main periods of development?
no
Which stages are there and what does each stage come with?
zygote, embryo and fetus
specific biological changes
Germinal period (duration)
first two weeks after conception
embryonic period(duration)
- to 8. week after conception
Fetal period (duration)
- week until birth
When and how does pregnancy begin?
at conception (fertilisation)
sperm cell penetrates wall of egg cell (ovum)
-> zygote
Where does the fertilisation process normally take place?
inside the Fallopian tube
How does the germinal period start and how long does it last?
with fertilisation
first 14 days
What happens between fertilisation and the implantation into the uterus?
duplication of cells via mitosis
-> until it forms a blastocyst (4-5 days after fertilisation)
-> differentiation of cells into trophoblast (shell) and embryoblast (nucleus)
What will happen with the trophoblast and embryoblast after implantation into the uterus?
trophoblast: structures responsible for nutrition and protection of the embryo
embryoblast: becomes embryo
How does the germinal period end?
blastocyst implanted in wall of uterus
Why does the blastocyst implant itself into the wall of the uterus?
to receive mother’s blood supply
How many zygotes don’t achieve implantation and thus die?
50-75%
When does the embryonic period begin and end?
after implantation (2 weeks) until 8th week
Amnion
becomes amniotic sac surrounding the embryo (fluid-filled)
-> shock absorber
-> maintains temperature
-> reduces weight and facilitates movement
Yolk sac
produces blood cells for embryo until it has its own supply
Allantois
becomes umbilical cord
Chorion
becomes lining of placenta
Placenta
semi-permeable membrane embedded in uterus
separates mother from embryo
What passes through the placenta?
oxygen
carbon dioxide
sugars
proteins
fats
What does the embryo receive from the mother via the umbilical cord?
Maternal blood carrying oxygen and nutrients
Why can we say that the placenta is the site of all metabolic transactions between mother and embryo?
Embry receives oxygenated blood from mother and removes carbon dioxide and metabolic waste via the placenta
What is the embryoblast?
embryonic disc
consists of 3 layers of cells that will form all tissues and organs
What does the ectoderm layer of the embryoblast become? (outer layer)
nervous system, skin and hair
What does the mesoderm layer of the embryoblast become? (middle layer)
muscles, bones and cardiovascular system
What does the endoderm layer of the embryoblast become? (inner layer)
digestive system, lungs, urinary tract and other internal organs
What does the neural tube develop from, how and when does that happen?
primitive streak in ectoderm folds into neural tube
third week post-fertilisation
What develops in the 4th week (before anything else)?
4th: head, eyes, nose, ears and mouth
What is another major step in the embryonic period, related to the cardiovascular system?
minuscule blood vessel begins to pulsate
-> will later become heart
What develops in the 5th week?
retina and lenses
arms and legs (with webbed fingers and toes)
What happens in the 7th week?
finger and toes separate
rudimentary skeleton formed
What does the rapid development of the brain in the 5th to 8th week allow the embryo to do?
contract muscles and make sporadic movements (not voluntary)