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), 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.
* A hen requires between 24 and 26 hours to produce an egg.
* Thirty minutes after laying an egg she starts all over again.
* Most female animals have two functioning ovaries, but hens only use one, their left. The right ovary stays dormant.
* A female hen is born with thousands of tiny ova which will one day become egg yolks.
* A double-yolker egg is the result of two yolks being released at the same time.
* During formation, the egg moves through the oviduct small end first.
* Just before laying, it is rotated and laid large end first.
* Laying an egg is known as oviposition.
* The size of the eggs increase as a hen gets older.