If you raise backyard chickens, you’ve probably collected plenty of fresh eggs without thinking much about what’s inside them. We all know about the shell, egg white, and yolk, but a chicken egg has much more than those three familiar parts.
Every egg has several layers and structures that serve a purpose, whether to protect the contents from bacteria, provide nutrition, or support the development of a chick if the egg is fertilized. Even the little white strands you sometimes see when cracking an egg have a specific job.
Understanding chicken egg anatomy can help you recognize what’s normal, learn how eggs develop inside a hen, and make better decisions about collecting, cleaning, and storing your eggs.
Let’s look at the different parts of a chicken egg, along with some common questions backyard chicken keepers have about their eggs.
Parts of a Chicken Egg and What They Do
A chicken egg may look simple from the outside, but several parts work together to protect and support what’s inside. Here’s a closer look at the main structures and what each one does.
Eggshell
The eggshell is the hard outer covering that protects the egg’s contents. It’s made primarily of calcium carbonate, which gives it strength while still allowing gases to pass through thousands of tiny pores.
These pores let oxygen and carbon dioxide move through the shell, which is especially important as a fertilized egg develops into a chick. The shell also helps protect the egg from damage and limits moisture loss.
Eggshell color depends largely on the breed of the hen. Brown, white, blue, and green eggs may look different, but shell color alone doesn’t determine an egg’s nutritional value.
Bloom or Cuticle
A freshly laid egg has a thin outermost coating called the bloom, or cuticle. This natural protective layer covers the shell’s tiny pores and helps reduce moisture loss and bacterial invasion.
The bloom is especially useful for backyard chicken keepers because eggs can come into contact with dust, nesting material, and bacteria after they’re laid. Along with the shell and its membranes, this coating provides extra protection against contamination.
Washing an egg can remove or damage the bloom, which is why proper cleaning and storage matter.
Outer and Inner Shell Membranes
Just beneath the shell are two thin layers: the outer shell membrane and the inner shell membrane. These semipermeable membranes protect the egg’s contents while allowing gases and some moisture to pass through.
Together, the inner and outer membranes provide another barrier against bacteria entering through the shell. You may have noticed them when peeling a hard-boiled egg. They’re the thin, papery layers that sometimes stick to the shell or the egg white.
Air Cell
The air cell is a small pocket of air that forms between the two shell membranes, usually at the wider end of the egg.
When a fresh egg is first laid, it’s warm. As the contents of the egg cool, they contract slightly, creating an air space between the membranes.
Over time, an egg gradually loses moisture through its shell, causing the air cell to grow larger. This is one reason older eggs are more likely to float when placed in water.
Egg White or Albumen
The egg white, also called albumen, surrounds the yolk and makes up much of the egg’s contents. It’s mostly water but also contains different proteins that provide nutrition and help protect a developing embryo.
There are both thick and thin albumen layers. In a fresh egg, the thicker white stays close to the yolk, while the thinner white spreads farther across the surface when you crack the egg.
As an egg ages, the thick albumen becomes thinner, which is why older eggs tend to spread out more in a frying pan.
Chalazae
Have you ever cracked an egg and noticed white, twisted strands attached to the yolk? Those are called chalazae, and they’re completely normal.
Chalazae help keep the yolk near the center of the egg. They’re made of egg white strands and are safe to eat.
They’re often easier to see in a fresh egg because the albumen is thicker and holds its shape better.
Vitelline Membrane
The vitelline membrane is the thin covering that surrounds the yolk. It holds the yolk together and separates it from the egg white.
In a fresh egg, this membrane is usually strong enough to keep the yolk rounded when you crack it into a bowl. As the egg ages, the membrane gradually weakens, making the yolk more likely to flatten or break.
Egg Yolk
The yolk is the egg’s yellow or orange center and contains much of its fat, vitamins, and minerals. If an egg is fertilized, the yolk serves as a major source of nutrition for the developing chick.
Egg yolks provide a major source of vitamins (A, D, E, and several B vitamins), including riboflavin and thiamine. They also contain minerals such as phosphorus and iron, along with cholesterol and choline.
The yolk is also a source of lecithin, an effective emulsifier in cooking. That’s why egg yolks are useful in recipes like mayonnaise and salad dressings.
Yolk color ranges from pale yellow to a magnificent deep orange, depending largely on the hen’s diet. Hens that eat more carotenoid-rich foods often produce darker yolks, although color alone doesn’t tell you whether an egg is healthier or fresher.
Germinal Disc
The germinal disc is a tiny white spot on the surface of the yolk. This is where an embryo begins developing if the egg has been fertilized.
In an unfertilized egg, the spot is called a blastodisc. In a fertilized egg, early cell division creates a structure called a blastoderm.
As a fertilized egg develops during incubation, blood vessels eventually spread across the yolk to help transport nutrients to the growing chick.
The yolk itself doesn’t become the chick. Instead, the embryo develops from the fertilized germinal disc and uses the yolk for nourishment.
Why Do Chickens Lay So Many Eggs?
One interesting thing about chickens is that hens don’t need a rooster to lay eggs. Egg laying is part of their natural reproductive cycle, and a healthy hen can continue laying whether or not her eggs are fertilized.
People have also selectively bred domestic chickens over many generations to produce more eggs than their wild ancestors. Some productive laying breeds can produce five or six eggs per week during their peak years, but this depends on the breed, age, nutrition, daylight, and the hen’s overall health.
A hen’s body releases a yolk from her ovary, which then travels through the oviduct. Along the way, the egg white, membranes, and shell form around it. The shell develops in the shell gland, also called the uterus, before the completed egg is laid.
The entire process generally takes about 24 to 26 hours. That’s why most hens lay no more than one egg per day, and even productive hens don’t necessarily lay every single day.
What Part of the Egg Becomes the Chicken Embryo?
The part of the egg that develops into a chicken embryo is the germinal disc, which appears as a small white spot on the surface of the yolk.
It’s easy to assume the entire yolk eventually becomes a baby chick, but that’s not how it works. The yolk actually serves as the developing chick’s food supply, providing fats, vitamins, and other nutrients throughout incubation.
When an egg is fertilized and kept under proper incubation conditions, cells in the germinal disc begin dividing and developing into an embryo. As development continues, blood vessels form around the yolk to help deliver nutrition to the growing chick.
Egg white also plays an important role by providing water and protein. Under normal incubation conditions, a fertilized chicken egg hatches in about 21 days.
Is There Sperm in a Chicken Egg?
If you’ve ever noticed white, stringy material attached to an egg yolk, you might have wondered what it is. Some people mistakenly believe these strands are rooster sperm, but they’re actually called chalazae.
The chalazae are normal parts of the egg that help keep the yolk centered. They’re present in both fertilized and unfertilized eggs, and eating them is perfectly fine.
When a rooster mates with a hen, the hen’s reproductive tract can store sperm and use it to fertilize eggs as they’re released from the ovary. Fertilization occurs early in the egg-forming process, before the egg white and shell develop.
The white strands you see when cracking an egg aren’t sperm and don’t indicate whether an egg has been fertilized.
Can a Chicken Lay Two Eggs a Day?
Most hens lay no more than one egg per day because producing an egg takes approximately 24 to 26 hours. In fact, even hens known for excellent egg production don’t necessarily lay every day.
Occasional reports suggest hens can produce two eggs in a short period, but this is unusual and may happen when the laying cycle is irregular.
You’re much more likely to encounter a double-yolk egg. This happens when a hen releases two yolks close together, and both end up in the same shell.
Double-yolk eggs are particularly common in younger hens whose reproductive systems are still developing. They’re generally safe to eat when handled and cooked properly.
Is an Egg a Dead Chicken?
No, an unfertilized egg isn’t a dead chicken. It’s simply an egg that hasn’t been fertilized and therefore cannot develop into a chick.
Hens naturally lay eggs even without a rooster. These eggs still contain the yolk, albumen, shell membranes, and other normal structures, but no developing embryo.
Even a fertilized egg won’t automatically become a chick. It needs the right incubation conditions to continue developing. Without those conditions, a fertilized egg won’t complete the process of becoming a baby chicken.
Can You Eat an Egg Right After It Is Laid?
Yes, you can use a freshly laid egg for cooking right after collecting it. There’s no need to wait several days before eating eggs from your backyard chickens.
However, fresh eggs aren’t automatically free from bacteria. Eggs can become contaminated during laying or from contact with dirty nesting materials, manure, or other surfaces.
Keeping your nesting boxes clean, collecting eggs regularly, and washing your hands after handling them can help reduce contamination risk.
For the safest approach, refrigerate collected eggs promptly and cook them thoroughly. Freshness is nice, but proper handling is just as important.
Should You Run an Egg Under Water to Clean It?
Fresh eggs have a natural protective coating called the bloom, which helps prevent moisture loss and reduces the chance of bacteria entering through the shell’s tiny pores.
Washing can remove this coating, especially if you scrub eggs or handle them improperly. If an egg has only a little loose dirt on it, carefully removing the debris with a dry cloth or brush may be enough.
When eggs need washing, use water warmer than the egg, avoid soaking them, and dry and refrigerate them promptly. Discard eggs that are cracked or heavily contaminated with manure.
It’s also worth remembering that commercially sold eggs in the United States are generally washed and refrigerated before reaching grocery store shelves.
What Is the White Stuff You Find When You Crack an Egg?
Those white, stringy pieces you sometimes notice attached to the yolk are called chalazae. They might look a little unusual, but they’re a perfectly normal part of chicken egg anatomy.
Each egg typically has two chalazae that help keep the yolk suspended near the center. They’re made from thickened strands of albumen and are completely edible.
You may notice the chalazae more easily in a fresh egg because the egg white is thicker and the internal structures are more defined. As an egg ages, the albumen gradually thins, and the chalazae can become less noticeable.
You don’t need to remove them before cooking, but you can if you prefer.
Can You Eat Eggs With Blood Spots?
Finding a small red or brown spot inside an egg can be surprising, especially if you’re new to raising backyard chickens. Fortunately, a blood spot doesn’t mean the egg was fertilized or that a baby chick started developing.
Blood spots usually form when a tiny blood vessel breaks during egg formation. They can appear on the yolk or elsewhere inside the egg.
Small blood spots are generally harmless, and you can still use an otherwise normal egg after proper cooking. If the spot bothers you, you can simply remove it with a spoon.
However, if an egg has an unusual smell, widespread discoloration, or other signs of spoilage, discard it.
Why Do Chickens Keep Laying Eggs if They Can’t Make Chicks?
Hens continue laying eggs without a rooster because egg production is part of their natural reproductive cycle. A rooster is needed for fertilization, but not for the hen to ovulate or form an egg.
As a yolk is released from the ovary, it travels through the oviduct, where the remaining parts of the egg develop. This process happens whether or not the hen has mated.
Breeders have also selected domestic chickens to lay eggs frequently, which is why some backyard breeds produce hundreds of eggs each year.
However, egg production isn’t constant throughout a hen’s life. Most hens naturally slow down as they age, and laying can also decrease during shorter winter days, molting, illness, or periods of stress.
Can Fresh Eggs Be Stored at Room Temperature?
You may have seen backyard chicken keepers storing fresh eggs in baskets on the kitchen counter. Some countries commonly store unwashed eggs at room temperature, but food safety recommendations vary depending on how the eggs are handled.
For backyard chicken keepers in the United States, refrigeration is the safest general recommendation. Keeping eggs at 40°F or below helps reduce the risk of bacterial growth and keeps them fresh longer.
Once eggs are refrigerated, keep them refrigerated rather than moving them repeatedly between the refrigerator and countertop.
Eggs purchased from grocery stores in the United States have generally been commercially washed and must be kept refrigerated.
How to Check if an Egg Is Bad
One of the most common ways people check an egg’s freshness is with the float test. Simply place an egg in a bowl of water and watch whether it sinks, stands upright, or floats.
A very fresh egg typically sinks and lies flat on the bottom. As the egg ages, it gradually loses moisture and its air cell grows larger, causing it to become more buoyant. An older egg may stand upright or eventually float.
However, the float test tells you more about the egg’s age than whether it’s safe to eat. A floating egg isn’t automatically spoiled, and a sinking egg isn’t guaranteed to be free of harmful bacteria.
If you’re unsure about an egg, crack it into a separate bowl and check for an unusual odor or appearance. Discard eggs that smell bad or show signs of spoilage, and remember that harmful bacteria aren’t always detectable by sight or smell.
Proper refrigeration and thorough cooking are more reliable ways to reduce food safety risks than relying on the float test alone.
Understanding Your Backyard Chicken Eggs
A chicken egg has more than the shell, white, and yolk we see at breakfast. Each part serves a purpose, from the protective membranes beneath the shell to the yolk that nourishes a developing chick.
For backyard chicken keepers, understanding these structures makes it easier to recognize normal features such as chalazae, germinal discs, and occasional blood spots. It also helps explain why eggs change as they age and why proper handling and storage matter.
Whether you’re collecting your first fresh egg or have been raising chickens for years, knowing how eggs form and what happens inside them is useful.
