How well do you know your chicken’s eggs?

Eggs can tell you a number of things about your hen’s health – for example, whether your hen is stressed or even sick.

So it’s important to know about the different parts so you have a baseline, and if you plan to HATCH eggs, knowing them gets even more important!

As chickens evolved, their eggs developed for reproductive purposes, ot eating, so each part of the egg contributes to whether the embryo will hatch or not.

Here’s the different parts of an egg and what you need to know about them!


Air Cell

The air cell is located in the large end of the egg, and it’s what it sounds like – a place where air is stored.

When you hatch eggs, the air cell and its size becomes very important. As an egg ages, the air cell becomes larger, which is why older eggs float in water..


When we talk about “egg whites,” we’re referring to the albumen. It’s full of proteins, niacin, riboflavin, magnesium, potassium, and sodium.

A cloudy albumen means the egg is fresh. As the egg ages, the carbon dioxide escapes, leaving the albumen more transparent than their fresh counterparts.


This is the round white bullseye-looking spot you see in the yolk, and it’s where embryo begins to develop when the egg is fertilized and under hatching conditions (meaning, the egg is at the right temperature with the right humidity for hatching.)


The bloom of an egg is a natural coating that covers the eggshell and protects the interior of the egg from bacteria. It also reduces moisture loss from the egg, which is important for the hatching process.  

If you plan to hatch your eggs, you definitely don’t want to wash them, because it will eliminate the bloom.


Pronounced kah-layz-ah, the chalazae are the rope-like strands you see connecting egg whites to the yolk. The more obvious the chalazae are, the fresher the egg.

In nature, it’s an important part of the hatching process because stabilizes the yolk (which feeds the chick embryo as it grows) in the egg.

Membrane, Inner & Outer

The inner and outer membranes provide more protection for the eggs contents. The air sac is located between these two membranes on the large side of an egg.


The shell protects the albumen and yolk, and eventually the growing embryo. It’s mostly made up of calcium carbonate, which is why feeding your chickens a calcium supplement is so important. The shell is also made up of thousands of pores to allow gas exchange.

Vitelline Membrane

This membrane protects the yolk and keeps it from breaking. It weakens as the egg gets older, which is why yolks of fresh eggs stand up tall, while yolks in older eggs appear flatter.


The yolk is a protein and vitamin rich portion of the egg, and where the embryo begins developing in a fertilized egg. It’s also where 100% of the fat in eggs is contained.

Just before chicks are born, they absorb the yolk, which nourishes them for up to 3 days.

Curious about egg abnormalities like wrinkled shells, rubber eggs, and lash eggs? the carbon dioxide escapes


Maat van Uitert is a backyard chicken and sustainable living expert. She is also the author of Chickens: Naturally Raising A Sustainable Flock, which was a best seller in it’s Amazon category.  Maat has been featured on NBC, CBS, AOL Finance, Community Chickens, the Huffington Post, Chickens magazine, Backyard Poultry, and Countryside Magazine. She lives on her farm in Southeast Missouri with her husband, two children, and about a million chickens and ducks. You can follow Maat on Facebook here and Instagram here.

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One Comment

  1. This was very informative and educational! I think I have had at least one of each of the ten eggs described at one time or another from my chickens and was scratching my head with the “what the?” kind of confusion. You certainly answered a lot of questions for me. I will definitely take pictures of my next strange egg and send it to you.
    Thank you so much for all your great information it has helped me become a much better chicken owner!

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