The Visible EmbryoHome
Home----History-----Bibliography-----Pregnancy Timeline-----Prescription Drugs in Pregnancy---- Pregnancy Calculator----Female Reproductive System----News Alerts----Contact

Carnegie Stage 3 - First Trimester
Cartilage transforming
into bone

SIZE: 19.0 - 24.0 mm

TIME PERIOD: 54 - 56 days post-ovulation

Head and Neck
Head developing the fissures characteristics of humans. Eyelids and external ear more developed and the upper lip fully formed. The brain can move muscles.

The critical period of heart development ends. It will continue to develop, but not at such a quick pace.

In female embryos, the clitoris is beginning to form. The penis will develop from the same tissue.

Fingers lengthen while distinct grooves (digital rays) form between the fingers, which also lengthen as the hands approach each other across the abdomen. Feet approach each other, but are still fan-shaped and the toe digits are still webbed.

Primary ossification centers appear in the long bones, directing the replacement of cartilage by bone. This process usually begins in the upper limbs. Fingers overlap those of opposite hand, and the digits of the fingers fully separate. Feet lengthen and become more defined.

Spine, Skeleton, and Muscles
The stubby tail is still present, but much smaller.

original work, are licensed under a

Creative Commons License

Content protected under a Creative Commons License. No dirivative works may be made or used for commercial purposes.