Embryonic Development Flashcards
How is an embryo formed?
When an ovum is fertilised it becomes the diploid zygote(cell formed by fusion of sperm and egg)
What is a blastocyst?
A hollow ball of cells at day six of the embryonic development
After implantation what occurs?
Outer cell later beings to forms the placenta and the inner cell mass(clustered to one side) begins to develop into the embryonic disc and the amniotic sac and yolk sac
What is an embryonic disc?
What will develop into an embryo. It has three germ layers.
What are the three primary germ layers?
Ectoderm- becomes the skin and nervous system
Mesoderm- becomes the body tissues
Endoderm- becomes the organ system
What occurs after 1 month of growth?
- the embryo is 4mm long
- mesoderm developed into brain and spinal cord
- heart and liver begin to develop
- clefts in throat form the face and throat
What occurs after 5 weeks of growth?
Limbs buds begin to develop
At 6.5weeks what events occur?
- limb buds are more prominent
- tail is disappearing
- face has greater definition
When is the end of the embryonic period?
At week 8.
- embryo is 3cm long
- weighs 1g
- jaws, nose and ears are almost developed
- fingers and toes are present
- sex organs are present
What is an embryo?
Refers to the developing organism from conception until the end of the 8th week
