Baby: Week 2
The baby at the second week of development
Differentiation begins – the process of cells adopting different functions as they multiply rapidly. You’re now like a triple layer cake. The neural tube is the top layer; it will later be the point of growth for your brain, spine and nerves. In the middle layer, your heart and circulatory system are appearing. In the innermost layer are your lungs, intestines and a very rudimentary urinary system. Amazing after only two weeks, isn’t it?
The fertilised yolk sac is supplying you with red blood cells and nutrients, but as that won’t last long, there is already a new system under construction to deliver maternal nutrients to you – the umbilical cord, joining you to your mother through the placenta, will be ready soon! The umbilical cord is the delivery mechanism for nutrients and oxygen to reach you from the placenta.
All this amazing growth happens in miniature! You’re about 1/25th of an inch long, roughly as big as a pinhead.[3 At this early stage of life, you’re known as an ‘embryo.’
Langmans Medical Embryology, Ninth Edition, TW Sadler, 2003find out more
Babycentre discusses Week 4find out more
WebMD - Your Pregnancy - Weeks 1 - 4find out more