Which Came First The Egg or The Chicken

What Came First, the Chicken or the Egg?

While the jury might still be out on this one, what we do know is that eggs would be the cherry on top when it comes to poultry keeping. But how much can you really know about these gems that are wholesome?

We are here to set the facts straight and also inform you exactly what you might ever want or need to learn about eggs!

What is an Egg?

A chicken egg could be either fertilized or unfertilized, and is the perfect little package (an average-sized egg weighs about 50 grams, however this will vary based upon the chicken breed), comprised of seven basic parts; the casing, membranes, the albumen (white), the yolk, the chalazae, the germinal disc and the air sac. Each one of these parts have a specific work to do and serve a particular function.

anatomy of a chicken egg
Anatomy of a Chicken Egg


The eggshell is a really intriguing piece of engineering, housing the entirety of these eggs components inside. It’s composed almost entirely of calcium carbonate, and covered in tiny pores, which give the egg its grainy texture. The casing is a semipermeable membrane, which is just fancy talk for significance that moisture and air can pass through it’s pores. Additionally it is protected by a thin outermost coating called the’bloom’ or’cuticle’, that acts as a natural barrier against external pathogens such as bacteria and dust.


The egg has 2 membranes-outer shell membrane and inner shell membrane, which both sit just inside the shell surrounding the albumen (white). These super strong transparent protein membranes, which can be made partially of keratin, have the function of protecting against bacterial invasion. The outer membrane is secured to the egg shell, whereas the inner membrane sticks into the albumen.


Albumen (White):

The albumen, more commonly called the’white’, is composed of vitamins, minerals, protein and water and is made up of three primary parts-an inner, middle and outer layer, each of varying depth which surround and protect the yolk. These powerful layers contain plenty of proteins which in a fertile egg can assist with the chicks development, or if sterile, will be passed on to us!

The Yolk:

The yolk is the fundamental portion of an egg, and while generally yellowish, its color may change based upon the chicken breed, which range from a light yellow to a deep orange. This tiny powerhouse is where the majority of the proteins, minerals, vitamins and fats of the egg are housed, such as Vitamin A, D, phosphorous, calcium, thiamine and riboflavin.


Chalazae are a part of the egg and are sequences of twisted tissue positioned at opposite ends of the yolk. They play the important role of stabilising the yolk and germinal disk to stop twisting and misalignment from the egg.

Germinal Disc:

Also referred to as the egg cell, or blastodisc, the germinal disc sits on the surface of the cover of the egg yolk and is the ‘powerhouse’ of the egg, as it is where the sperm enters the egg. It is here that the embryo will form by a process of cell division and expansion after fertilisation has occurred.

Air Sac:

Sometimes called the ‘air space’ or ‘air mobile’, the air sac forms once the contents of a newly laid egg cools, causing them to contract. This air sac rests between the inner and outer membranes in the eggs bigger end. As the egg matures and not get fertile, the air sac will expand because of moisture and carbon dioxide leaving the egg, and air going into the egg to replace them.

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So now you understand just what constitutes these all natural wonders, you are likely asking just how a hen can make this kind of protein packaged product?!  Keep reading to find out…

A productive egg layer does first and foremost be based on the chicken strain, so ample research ought to be undertaken in this respect if you are wanting chickens for the sole purpose of the egg producing capabilities. In addition to this they have to be given a balanced and nutritious diet (high in calcium and protein ), fresh water, lots of sunlight, in addition to nesting boxes which are conducive to egg laying (fresh straw, broad, and from the way of direct sunlight or drafts).

A female chicken is born with a complete complement of eggs inside her body, and depending on the strain, will create many or hardly any eggs through the years. Chickens have thousands of miniature ova, which are undeveloped yolks in their gut, and if they’ve matured, an ovum is going to be released into the oviduct where it begins it’s great journey of growth. A hen can have many eggs at various stages of development inside her reproductive system at the same time. Those at the start of their journey are only small yolks, whereas the eggs which are farther down the oviduct are markedly larger and more developed. It takes about 25 hours for an egg to reach the vent prepared for planting in the time it leaves the ovary. Within this period the yolk will expand and become encased from the albumen, wrapped in a membrane and then enclosed in a pigmented shell-voila! Fresh eggs for everybody!

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The first stage of embryo growth happens in the blastodisc (germinal disk ), which will become known as the blastoderm once fertilised, and it includes genetic material from both the chicken and the rooster. If housed in the perfect states, either via incubation or by a hen, these cells will then develop into a chick embryo, where it will grow and further develop, getting nourishment from the yolk and albumen.

We think it’s safe to say that there’s definitely far more than meets the eye when it comes to the humble egg. Next time your hen lays one of these beauties take some time to applaud and appreciate these natural wonders!

WATCH THIS SHORT VIDEO AND WE HOPE YOU’LL FIND THE ANSWER AFTER…Please leave some comments if you find this interesting. Thanks!


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