Eggs are one of the most versatile foods around. They can be the star of the show (omelette, quiche), the supporting actor to other ingredients (pad thai, spaghetti carbonara) or the hidden hero by making a cake rise or giving a soufflé its fluff.
Even though eggs are used all the time in cooking, not many people really understand how they are made inside a hen.
An egg develops through multiple stages during its time inside a hen. A yolk is encased in layers of egg white and protective membranes, sealed within a shell and coated with a fast-drying protective fluid.
There are a lot of questions about how eggs are made inside hens. This page will help you find the answers.
One of the healthiest and most useful foods in nature is the egg. But even though eggs are very popular, a lot of people are curious about where they come from and how they are made. This article tells you everything you need to know about eggs and how chickens lay them.
Egg Anatomy
Before diving into egg laying, it’s helpful to understand the basic anatomy of a chicken egg. An egg contains the following key parts:
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Shell: This tough, porous covering keeps germs and damage from getting into the egg. It’s made in the hen’s oviduct just before the egg is laid.
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Inner and outer membranes – These thin membranes line the inside of the shell to protect and cushion the egg
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Air cell – An air pocket forms at the rounded end of the egg as it cools after laying. This allows the contents to expand and contract.
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Chalazae – Rope-like strands of egg white that anchor the yolk in the center of the egg
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Albumen (egg white) – The protein-rich clear or cloudy liquid that surrounds the yolk. It provides nutrition and protection.
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Yolk – The yellow, nutrient-dense center of the egg where the embryo develops into a chick (if fertilized). It is a major source of vitamins, minerals, fat and protein.
Egg Formation and Laying
Chicken eggs begin their journey in the hen’s ovary. When a yolk matures, it is released into the oviduct, where egg components are added in sequence until the whole egg is formed. The main steps of egg production are:
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Yolk formation – The yolk develops in the ovary in a process called ovulation, taking around 25 hours to mature. Once released, the yolk travels to the oviduct.
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Albumen layers added – In the oviduct, layers of thin albumen are deposited around the yolk over approximately 3 hours. Thick albumen is added last.
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Shell membranes are put on—Two shell membranes are made around the egg contents in the oviduct’s isthmus area. These take around 1. 5 hours to complete.
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Shell formation – The egg moves to the uterus where the shell is gradually deposited, taking around 20 hours. Calcium carbonate forms the shell’s crystalline structure.
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Pigment application – Colored breeds add pigment to the shell as the last step, creating brown or blue eggs rather than white.
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When a bird lays an egg, its muscles contract and push the egg out through the vent. This process takes just seconds.
How Often Do Hens Lay Eggs?
Laying frequency depends on factors like breed, diet, age and season. Most hens ovulate about once per day, so they cannot lay more than this. Breeds developed for commercial egg production tend to lay very regularly, producing 5-6 eggs per week. Heritage breeds may only lay 1-2 times per week.
As chickens age, their laying slows down. They experience natural declines in hormone levels and oviduct function over time. Molting, cold weather and stress can also temporarily stop egg production.
Free-range, well-fed hens with adequate space typically have the best laying rates. Clean nest boxes encourage hens to lay in the right spot.
Can You Eat Eggs From Backyard Chickens?
Absolutely! In fact, eggs from backyard flocks are often superior in flavor and nutrition compared to store-bought. The “bloom” coating on very fresh eggs helps protect their quality. As long as you provide hens with proper feed and housing, their eggs are perfectly safe to eat.
The color of the shell has no effect on nutritional content. However, local eggs tend to be richer with brighter orange yolks due to natural foraging. Store-bought eggs often come from caged hens fed unnatural diets.
As always, proper handling and cooking is important for safety when eating any eggs. But the notion that eggs from family flocks are unsafe is simply a myth. The chickens, eggs and humans all benefit when small backyard flocks are raised responsibly.
How Is an Egg Formed?
A laying hen’s ovary holds thousands of tiny ova, or future egg yolks. Birds are different from other animals because only one ovary (the left) grows to the point where it can release eggs.
When the yolk is ready, it leaves the ovary and goes into the oviduct, which is a tube-like structure with different sections. The egg white protein is added to the yolk over the course of four hours as it moves through the magnum, a part of the oviduct.
There are many different proteins that make up the egg white. The different protein layers provide protection for the yolk and create a template for the formation of the shell membrane and shell.
After quickly moving through a section called the isthmus where shell membrane fibres are produced, the egg enters the shell gland where the shell forms over about 20 hours. The process is called calcification as layers of calcium carbonate are added to form the shell.
During the last two hours of shell formation the bulk of the pigment (white or brown) is produced and deposited into the outer layers of the shell. This includes the cuticle which is laid down to provide protection against bacteria that might try to penetrate the shell and potential loss of water from the egg’s contents.
The egg then rotates just before laying to be laid large end first, having moved through the oviduct small end first.
Learn More About Egg Production in Australia
Eggs are produced using different methods with the three most common being free range, barn-laid, and cage. While each system has its advantages and disadvantages, the nutritional profile of the eggs is consistent across all systems.
Learn more about these different farming systems today or take Australian Eggs interactive tour of three commercial egg farms.
What Came First The Chicken or The Egg? | The Most Confusing Question | The Dr. Binocs Show
FAQ
Which hole does a chicken egg come out of?
It might sound a little dirty, but eggs and poo come out of the same part of the chicken. It’s kind of like a plumbing system: two “pipes” meet at one outlet, which in this case is the chicken’s ovaries. In humans, we call this the anus (the bumhole).
How does a rooster fertilize the egg?
A rooster fertilizes a hen’s egg through a process called the “cloacal kiss,” where the rooster’s cloaca (the common opening for reproductive and digestive tracts) touches the hen’s cloaca.
Where on a chicken does the egg come from?
A laying hen’s ovary holds thousands of tiny ova, or future egg yolks. Birds are unique among animals because only one ovary (the left) matures to the stage where it releases eggs. When a yolk is ready, it moves out of the ovary and into the oviduct – a tube-like structure that is divided into different sections.
Do chickens have only one hole?
Getting to Know the Cloaca: Unlike humans and most mammals, a female chicken only has one rear opening that serves three purposes. It is where feces and eggs exit her body and sperm enter. The rooster’s cloaca has only two functions. One is to pass feces.