Egg Formation in Hen
The egg is formed gradually over a period of about 25 hours. Many organs and systems help to convert raw materials from the food eaten by the hen into the various substances that become part of the egg.
The hen, unlike most animals, has only one functional ovary – the left one – situated in the body cavity near the backbone. At the time of hatching, the female chick has up to 4000 tiny ova (reproductive cells), from some of which full-sized yolks may develop when the hen matures. Each yolk (ovum) is enclosed in a thin-walled sac, or follicle, attached to the ovary. This sac is richly supplied with blood.
The mature yolk is released when the sac ruptures, and is received by the funnel of the left oviduct (the right oviduct is not functional). The left oviduct is a coiled or folded tube about 80 cm in length. It is divided into five distinct sections, each with a specific function, as summarised below
1 Funnel (infundibulum): receives yolk from ovary. If live sperm present, fertilisation occurs here (commercially produced table eggs are not fertilised) the time spent here is 15 minutes
2 Magnum : Albumen (white) is secreted and layered around the time spent here is 3 hours
3 Isthmus : Inner and outer shell membranes are added, as are some water and mineral salts the time spent her is 1 hour
4 Shell gland (uterus): Initially some water is added, making the outer white thinner. Then the shell material (mainly calcium carbonate) is added. Pigments may also be added to make the shell brown the time spent here is 21 hours
5 Vagina/cloaca : The egg passes through this section before.laying. It has no other known function in the egg’s formation the time spent here is less than 1 minute
If it takes hen 25 hours to form a egg that is more than one day, then it is not possible for a hen to lay more than one egg in a day.
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