G is for...Gizzard and Gravid.

G is for Gizzard. Following on with my ABC of life with the Nesbitt chickens we come to G!
Some technical information today!

A Gizzard is a compartment in the chicken's digestive system that grinds up food. It is lined with keratin and uses small stones (grit) to break the food down to smaller pieces.
Many other birds have this same organ.

The digestive process is as follows…
The beak moistens food with Saliva.
Food is not chewed. The oesophagus takes the food down to the crop to be stored.
After a chicken has eaten, the crop will feel full and bulge. Food from the crop slowly passes down to the proventriculus. The proventriculus mixes the food with acids and digestive enzymes. Food is then passed through to the gizzard where insoluble (flint) grit has accumulated.

 ( As our hens are free-range and allowed to forage wherever they please - they have sufficient grit in their natural diet. From time to time I add some grit but this is rare).

Food is ground down by strong muscular action in the gizzard. From the gizzard, food is passed through to the small intestine and is reduced further with enzymes from the pancreas. Bile produced by the liver and stored in the gall bladder helps to break down fat. The intestines digest the food, taking nutrients from it. Water and the remaining undigested food is absorbed in the large intestine.

 The caeca are a pair of tubes that allow fermentation of undigested food to take place. This is emptied every 24 hours or so and is a light brown (mustard colour) froth. This can often be confused as diarrhoea by the novice. The cloaca / vent passes a combination of faeces and urine, together with eggs from the oviduct. This is the only rear orifice chickens have. The name cloacae means "common sewer". Eggs travel through here to exit the body. Sperm enters here, and urine and faeces also exit the body through that pathway, hence the name.(Sorry were you eating?)

Gravid, A bird that is about to lay an egg is called "gravid," just like a woman who is about to give birth.
A female chick is hatched with one functioning ovary and all of the eggs (as in female gametes, not shelled eggs), that she will ever have.

Once she is sexually mature, she will lay one shelled egg about every 24 hours during each laying cycle.
A laying cycle lasts about 21 days.
The female gametes are called follicles. A number of them will develop at a time; the largest will get fertilized if sperm are present.

This large follicle is the egg yolk; it is intended to be nourishment for a developing embryo, and is referred to as a yolk sac. Whether fertilized or not this yolk sac passes through a series of organs to become a shelled egg.

 Its first stop is an organ called the infindibulum, wherein that sticky membrane surrounding the yolk sac (called the chalazae) is deposited. This takes about 15 minutes.
 The next stop is an organ called the magnum, where the albumin, or egg white, is formed; this takes about 3 hours.
Next it goes to an organ called the isthmus, where shell membranes are formed; this takes about one hour.
The last stop is the uterus, or "shell gland," and this is where the shell is deposited and becomes mineralized. This last step takes the most time, about 20 hours.

Then the egg is then ready to be laid.

Fascinating eh? Now you know.

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