Alcoa Anglesea day 7

Embryonic development, day 5

Embryo on day 5

Day 5

The embryo uses oxygen and disposes of CO2. Both have to be transported from and to the embryo. In the first 2-3 days the early embryonic germ layers (ectoderm, mesoderm, and endoderm) in the blastoderm are just few and so oxygen can be obtained easily. But as soon as the layers increase the embryo needs a infrastructure within the egg for the oxygen, bourishment and protection.

The 3 extra embryonic membranes are formed from the primitive germ layers within the egg. Everything needed for the development of the embryo is on board of the egg. Water, nourishment and energy like fat are there for tissuegrowth and everything needed to maintain the proces. The only things needed are warmth and oxygen.
On the 5th day of the emebryonic development:

* The somites extend to the tip of the tail.

* The toes begin to form.

* The allantois is visible coming off the hindgut.

* The allantoid circulation is commencing

* The Erythropoiesis starts in the yoke sac

* The embryo starts to move with head and neck region

* The amnion strats to contract

* The proteinase is starting