OCB02-1003 Embryogenesis Flashcards
How is the blastocyst formed
When the egg and sperm fuse, they form a zygote, which undergoes cleavage, and replicates to form a ball of cells
How many cells are there in a blastocyst?
128
What is the blastocyst comprised of?
An inner cell mass which contains the embryonic stem cells
An outer layer of cells called the trophectoderm
The blastocele which is a fluid filled cavity
What process occurs 6 days after fertilisation?
Implantation
What occurs during implantation?
The trophoblast cells begin to infiltrate the wall of the uterus
What process takes place after cleavage an formation of the blastocyst?
Gastrulation
Overall what does gastrulation do?
It reorganises the bilaminar disc int the 3 germ layers?
What is the bilaminar disc made up of?
Epiblast layer
Hypoblast layer
What are the names of the 3 germ layers?
Ectoderm
Mesoderm
Endoderm
How does the bilaminar disc form?
The inner cell mass divides into the epiblast and hypoblast
What forms as the epiblast and hypoblast grows and is the site of gastrulation?
Primitive streak
What occurs during gastrulation?
Cells in the epiblast move towards the primitive streak
Cells leave the epiblast and ingress into the primitive streak
Ingressing cells form the endoderm as they are pushed into the hypoblast layer
Cells that come out of the epiblast later form the mesoderm
Cells that remain at the surface form the ectoderm
What are the derivatives of the ectoderm?
Skin
Nervous system
What are the derivatives of the mesoderm?
Vertebral column
Skelton
Skeletal muscle
Blood
What are the derivatives of the endoderm?
GIT
What do the position of cells along the primitive streak determine?
Their final position in the dorso-ventral axis
Where do cells from the anterior tip of the streak go to?
notochord
Where do cells from the posterior tip of the streak move to?
Paraxial somites of mesoderm
What initiates the neuralation process?
notochord
What is neuralation?
The folding process by which the neural plate forms the neural tube
What occurs in the process of neuralation?
The neural plate forms in the ectoderm and it broadens and its ends begin to fold upwards
As the fold gains height, a neural groove forms
The fold will eventually close to form the neural tube
What happens to the endoderm during neuralation?
The endoderm moves towards the midline of the body and fuses to create the primitive gut tube
What are the 3 sections of the primitive gut?
foregut
midgut
hindgut
What are neural crest cells and what will they form?
They are migratory cells that bud off when the neural tube was formed
They will form PNS and autonomic ganglion etc
What will neural tube form?
The brain and spinal cord
What is another name for the head and tail axis?
Rostral- caudal
