Firstly the hen releases a yolk from her ovary.
The infundibulum (also known as the funnel) holds the yolk for about 15 minutes (this is where fertilisation would take place if there was a rooster around) before it passes to the magnum, where, after three hours the white is formed.
As the white (albumen) is deposited around the yolk it rotates, twisting the albuminous fibres to form the chalazae.
The next site of activity is the isthmus where the two shell membranes are formed in about 1¼ hours. The egg has now reached it full size and shape. It passes along to the uterus to acquire, after 19 hours, its shell, shell colour and bloom, or protective coating. After a few minutes pause in the vagina, the uterus inverts the cloaca (the junction of the digestive, urinary and reproductive systems) and the vent and the egg is laid. All in a day’s work so to speak.