Week 7 development includes a lot of organ action. Your tiny ball of cells is the size of a blueberry, measuring about half an inch with an overall size that is double what it was last week! Imagine growing twice your size in only a week; it is no wonder you are exhausted and looking for a nap.
Your little embryo has a small tail and is 10,000 times larger than it was at conception. During this week, the majority of growth is taking place in the embryo's head as hundreds of new brain cells are being generated per minute. The heart's atrium, ventricles, and lung buds form along with limb buds, eye lenses, mouth, and tongue. While the embryo doesn't look human yet, it does look more human than ever before.
In addition to the heart, lungs, and brain, most other organs are also busy forming. The kidneys are in place; the appendix and pancreas are forming so they will be prepared to aid in digestion; the liver is creating red blood cells until bone marrow is ready to take over the role, and the intestines are pushing into the umbilical cord which is busy carrying oxygen and nutrients to and from the embryo to help facilitate and nourish growth.
- American Pregnancy Association - 1st Trimester Development