Anatomy of the Egg

The outer defences

Have you ever wondered what that white stringy bit attached to the yolk is called or what albumen is? Here is everything you ever wanted to know about the anatomy of an egg, and probably a little bit more!

1. Shell - The egg's first line of defence against bacteria. Can be white or brown depending on the hen's breed; the nutritional value is the same either way. It has approximately 10,000 tiny pores that allow moisture and gases in and out.

2. Air Cell - Formed at the wide end as the egg cools after laying. The fresher the egg, the smaller the air cell - this is exactly what the float test in PIP'S TIPS - How Old Are My Eggs? is based on.

3. Albumen (al-BYOO-min) - The egg white, roughly 2/3 of an egg's weight, made up of a thick and a thin layer. It's mostly water, high-quality protein, and minerals.

The inner workings

4. Yolk Membrane (vitelline membrane) - Surrounds and holds the yolk. The fresher the egg, the stronger this membrane is.

5. Yolk - The major source of vitamins and minerals, making up roughly 1/3 of an egg's weight. Its colour (light yellow to deep orange) depends entirely on the hen's feed, and doesn't affect the nutrition at all.

6. Chalazae (kuh-LEY-zee) - The spiral bands that anchor the yolk centrally within the thick albumen. These are actually more prominent in fresher eggs - so if you spot them, that's a good sign!

7. Germinal Disk - A slight depression on the surface of the yolk - this is the entry point for fertilisation, though of course our hens live happily without roosters, so ours never are.

8. Shell Membrane - The second line of defence against bacteria. There are actually two membranes inside the shell - one stuck to the shell itself, and one surrounding the albumen.

Now that you know what's inside, want to know exactly how fresh yours are? PIP'S TIPS - How Old Are My Eggs?