A hen lays one egg roughly every 25 hours and normally the yolk is produced and drops into the infundibulum, staying there for 15 minutes before passing down to the magnum. The yolk stays in the magnum for three hours where the white is secreted.
The egg passes into the isthmus and is here for one hour while two membranes form around it. It then spends the next 24 hours in the uterus where the egg shell is formed before being laid via the vagina and exits the vent.
Failure to pass the egg from the shell gland to the vent is referred to as Egg Binding (Dystocia) or more commonly as a hen being Egg Bound.
