Eggs undoubtedly come in a variety of sizes, shapes, eaten by many of us, and readily available in almost every country worldwide.

An egg is commonly made up of 6 parts:

* Shell
* Albumen (or white as it’s more commonly known)
* Membranes
* Yolk
* Chalazae (tissue that holds the yolk into the middle of the white)
* Germinal disc (known as the egg cell)

The Egg Shell

The egg shell is commonly more pointed at one end. And there is an exceptionally good reason for this odd shape. When a chicken lays an egg, and if the egg unfortunately begins to rolls, this unique oval shape prevents the egg from rolling away too far from the nest. This is because it rolls around in a circle! However, not all eggs are shaped like this, (such as the Pekin Duck for example) furthermore in the wild, this is an extremely useful feature, especially if you happen to be a seagull laying your eggs high in a nest on the edge of a cliff for example.

A large majority of the eggshell is developed and made up of calcium carbonate. This is the main reason why we need to provide a constant supply of calcium through correct nutrition and a good supply of oyster shell grit for our chickens.

Egg shells are incredibly porous and during incubation, this allows for a specific amount of moisture to leave and evaporate from an egg and also allows oxygen to reach inside the egg and carbon dioxide to exit out of the egg for respiration.

Egg shells are incredibly strong and durable but in their own right. The inside of the eggshell is significantly softer than the outside which allows a baby chick to be able to break through the shell to get out. This inner layer of the eggshell is also the calcium source which the baby chick uses to develop its bones.

Membranes

There are two membranes within the egg: an outer and an inner. The first outer membrane is attached to the eggshell. The stronger inner membrane provides separation between the outer membrane at the broader end of the eggshell. It’s possible to estimate the age of an egg just by looking at the size of the eggs air sack by using a bright light against the egg (known as candling). Freshly laid chicken eggs come with no air sack. Once they have naturally cooled, the air sack measures approximately 3mm.

Albumen or Egg White

The albumen or ‘egg white' as it’s more commonly known, contains vitamins, water, minerals and all the protein that the developing baby chick needs. The egg white acts like a jelly-like substance which acts like a built-in shock absorber if the egg is ever knocked. The egg yolk floats freely within the albumen. The egg white acts as the food that is slowly absorbed by the developing chick embryo inside.

Egg Yolk

The yolk is primarily made up of water, fats, proteins, vitamins and minerals. This food is absorbed by the developing chick through its abdomen before hatching and ensures the chick remains alive during the first few days of its life. This is why a day old chick can be shipped around the globe and why baby chicks can be left to dry out in an incubator without water or food for several hours.

Chalazae

The chalazae are a group of supporting spirals that hold and position the yolk in place. Each chalazae spiral is twisted in an opposite direction to one another.

Germinal Disc or Egg Cell

The germinal disc is the part of the egg where the female and male cells meet in fertile eggs, before beginning the cell division process.