Extra-Embryonic Formation Flashcards
What happens during the second week, when implantation is occurring?
A space begins to form between the ICM & the and the T (amniotic cavity)
Will soon fill with fluid and is the place were the baby will develop
How is the Embryonic Disk formed?
When as the AC forms, the ICM flattens, creating it - the ED is then supported by a short stalk that connects the blastocyst within the endo.
What is Gastrulation?
When the Embryonic Disk develops into 3 primary germ layers
What are the 3 primary germ layers crated during Garulation?
Ectoderm - outer layer, closer to the AC
Mesoderm - middle layer
Endoderm - inner layer, closest to the endo.
What is the embryo called after Gastrulation?
The Gastrula
Why is the development of the three germ layers so important?
All the cells, tissues and organs of the body are derived from them via differentiation
What is the Allantois?
It forms the foundation of the umbilical cord
Most degenerates during the 2nd month & the remainder becomes the urinary bladder
What is the Amnion?
A transparent sac that envelops from te embryonic disk
It grows to enclose the embryo completely (penetrated only by the umbilical cord)
Filled w/ amniotic fluid to protect the embryo from trauma and temp. fluctuations. Also allows for movement
& prevents limbs from sticking to the body
What is the Chorion?
Outermost membrane that encloses all the other extra-embryonic membrane & embryo
Forms the real portion of the placenta
What is the Yolk Sac?
Small sac suspended from the abdominal area of the embryo
Contributes to the formation of the digestive tract & produces the first blood cells and future egg or sperm cells
Serves no nutritive function in humans (unlike other vertebrates)
What is the Placenta?
A Disk-Shaped organ that is rich in blood vessels
Attaches embryo to the uterine wall
Metabolic exchange occurs through it
It’s fully developed by 10 weeks
Why do the blood systems of mother and child lie close to each other?
To allow for oxygen and nutrient/waste exchange through diffusion
NOTE: the placenta doesn’t filter out drugs, alcohol or nicotine, these substances can transferred to the baby if
the mother ingests them
How is the Umbilical cord formed? What is it?
Near the end of week 8, the yolk sac shrinks, amniotic sac enlarges and the umbiblical cord forms
It’s rope-like structure that leads fro the naval area of he fetus to the centre of the placenta
Contains 2 arteries which transport O2 depleted blood from the fetus to the placenta
Contains 1 vein which brigs O2 rich blood to the fetus
Has natural twists because the vein is longer than arteries
In 20% of deliveries the umbilical cord is wrapped around the neck
