Gastrulation
- Sperm fertilizes egg forming a zygote
- The cells of the zygote divide numerous
times.
- When the number of cells reaches ~32 it
forms a hollow ball called a blastula.
- As division continues an invagination
forms a hollow pocket in this ball of cells This is now called a gastrula,
the process is known as gastrulation.
- The opening of the gastrula is known as
the blastopore
- In Protostomes the blastopore
becomes the mouth
- In Deuterostomes the blastopore
becomes the anus
The hollow space is known as the Archenteron
- This results in the formation of three
dermal layers
- The ectoderm (forms outer covering
& nervous tissue)
- The endoderm (gut &
outpocketings like liver & lungs)
- The mesoderm (muscles & other
organs, forms later in the blastocoel of the gastrula)