The embryo is starting to look more and more like a tiny bird.
Day 10-11:
* Three rows of feather germs are visible on the tail.
* The nictitating membranes (inner eye lids) begins to form.
* The egg tooth begins to form.
* The bone marrow cavity of the femur begins to form.
* The leggs are bending at the knee
* Testosteron levels are rising
The little chick is starting to move in the egg. Just like a mamal embryo he is floating around in amnionfluid.
Embryo on day 11
Day 12
* Three rows of feather germs are visible on the tail.
* The nictitating membranes (inner eye lids) begins to form.
* The egg tooth begins to form.
* The bone marrow cavity of the femur begins to form.
Until now the skeleton is made up of cartilage. The proces of ossification is beginning from day 12. Ossification is the process of bone formation, in which connective tissues, such as cartilage are turned to bone or bone-like tissue. The ossified tissue is invaginated with blood vessels. These blood vessels bring minerals like calcium and deposit it in the ossifying tissue. Bone formation is a dynamic process, with cells called osteoblasts depositing minerals, and osteoclasts removing bone.[1] This process, termed bone remodeling continues throughout life.
Embryo at day 14
Day 13-14
* Upper eye lids begin to cover the eyes.
* The knee caps begin to form.
* The sero-amniotic tissue connection lies in the neckregion of the embryo
* Hematopoietic activity in the bownmarrow
* Thyroid glands produce di-iodo-tyrosine
