​Forming a human being from mere cells takes a lot of development and planning.

The weeks to come is a sensitive period where cells are telling one other where to go, and mapping out who's forming what. This process is called organogenesis.

The slightest defect can result in a malformation.

Sometimes, the error margins are too wide and this is not compatible with life. In such cases, the embryo will cease to develop and an early miscarriage would occur.

Mere cells are aligning themselves and obtaining symmetry.

One end will develop into the head, while the other gives rise to the tail end.

Pregnancy Week 5: Organ development begins!

By the end of pregnancy week 5, the beginnings of organ development would have taken place. It starts with 3 special layers of tissue called germ layers.

They are the:

  1. Ectoderm
  2. Mesoderm
  3. Endoderm

Each layer will develop into a certain set of organs.

The ectoderm is the outermost layer and will become the outermost skin, backbone, brain and nervous system.

The middle layer, or mesoderm will give rise to parts of the body such as the deeper layer of skin, bones, muscles, as well as the circulatory (including the heart) and immune systems.

The innermost layer, known also as the endoderm, grows into most of the digestive tract (stomach, liver, pancreas, intestines), urinary system and respiratory system.

By pregnancy week 10, all organ systems would have been formed, albeit immature and not fully functional.

Ref: N18