When an egg is fertilised, normally within the fallopian tube, it divides into a ball of cells with a hollow cavity called a blastocyst. 

The inner cell mass will become the develoing embryo and the outer layers of cells is the trophoblast that will give rise to the placenta. 

About seven day after fertilisation the blastocyst implants into the wall of the womb, also known as the uterus, and produces root-like outgrowths called villi, which anchor the egg into the endometrial lining. 

These villi grow into the placenta, which feeds and protects the baby until birth.


Diagrammatic version of blastocyst prior to implantation


Implantation banner courtesy of Flickr under the creative commons licence:

 Blastocyst image courtesy of Wikipedia under the GNU Free Documentation Licence:



First look at human ovulation in real time

10/12/2008 15:15
Ovulation, a rare event to see in humans, was observed during a partial hysterectomy.  For more information and the pictures relating to this see:


Understanding implantation can now give new insight to infertility

10/12/2008 14:16
A process that governs embryo implantation in the womb has been identified for the first time. The research could shed light on what goes wrong when embryos fail to implant in the lining of the womb, a leading cause of infertility. An MRC and Wellcome Trust-funded team published their findings in...


Fast Fact

Implantation bleeding can be quite normal in the early stages of pregnancy.  This bleeding is due to the fertilised egg burying into the endometrial lining of the uterus.  It should last between a few minutes to a few days.  If this bleeding continues you should consult a doctor immediately.