Complete Guide on 15 Parts of a Egg: Names, Functions & Diagram

Eggs have been a beloved food item for thousands of years, with evidence of egg consumption dating back to ancient civilizations such as the Greeks and Egyptians. Not only are they delicious, but eggs are also a great source of protein, vitamin D, choline, and selenium, making them a nutritious and accessible ingredient in kitchens worldwide. Each part of the egg serves a specific purpose, from the yolk, which contains nutrients and fat, to the white, which is rich in protein, to the shell, which protects the egg and helps to keep it fresh. Egg parts and their interrelation is itself a mystery.

Cooking with eggs offers endless possibilities, with techniques ranging from classic methods like boiling and frying to modern approaches such as sous vide cooking. Regardless of your skill level in the kitchen, there are countless ways to incorporate eggs into your culinary repertoire and create tasty, satisfying dishes.

From ancient times to the modern day, eggs have maintained their status as a staple food item, valued for their versatility and nutritional value. So why not try cracking open some eggs and exploring the endless possibilities in the culinary world?

Parts of an Egg Diagram

Parts of a Egg, Names & Diagram

Egg Parts Names

  • Eggshell
  • Outer & Inner Shell Membrane
  • Chalaza
  • Exterior Albumen
  • Middle Albumen
  • Vitelline Membrane
  • Nucleus of Pander
  • Germinal Disk (blastoderm)
  • Yellow Yolk
  • White Yolk
  • Internal Albumen
  • Air Cell
  • Cuticle or Bloom

Parts of an Egg & their Functions


Eggshells are one of the most intriguing and unique natural structures in the animal kingdom. Their exterior is composed almost entirely of calcium carbonate, a mineral that gives them their characteristic strength and durability.

What sets eggshells apart, however, are the up to 17,000 tiny pores that dot their surface. These pores allow for the exchange of air and moisture, creating a perfect environment for the developing embryo inside.

Additionally, the bloom or cuticle that covers the shell acts as a natural barrier, protecting the egg from dust and germs. Together, these features make eggshells a true wonder of nature and a testament to the intricate design of the natural world.

Outer & Inner Shell Membrane

The egg is a truly unique natural wonder, with a remarkable complexity and sophistication that showcases the ingenuity of nature. The egg’s specialized membranes, made primarily of keratin, are specifically designed to provide a formidable defense against bacterial invasion, ensuring the safety of the developing embryo inside.

As the egg cools, these membranes separate from each other, creating an air cell that allows the embryo to breathe and provides a nurturing environment for its growth.

This intricate design is a testament to the unique and unparalleled ingenuity of nature’s creations, and highlights the awe-inspiring power and complexity of the natural world.


One of the most interesting of these features is the chalazae, which are opaque bands of egg white that act like anchors, keeping the yolk centered within the egg.

These remarkable structures connect the yolk’s casing to the eggshell’s membrane, providing crucial support and protection during the early stages of development.

The chalazae’s visibility varies with the freshness of the egg, showcasing the complexity and sophistication of nature’s engineering. The egg’s intricate design and functions are a testament to the incredible ingenuity of the natural world, inspiring awe and wonder in all who encounter it.

Exterior Albumen

One of these features is the outer thin albumen, a narrow layer of fluid that sits next to the eggshell membrane. This seemingly unremarkable layer, however, plays a critical role in protecting the developing embryo, acting as a barrier against harmful bacteria and other potential threats.

Despite its simplicity, the outer thin albumen is an essential component of the egg’s intricate design, showcasing the remarkable ingenuity and sophistication of nature’s creations.

Middle Albumen

The chalaziferous layer of an egg is not only unique in its function but also in its composition. Unlike other parts of the egg, such as the shell or yolk, the chalaziferous layer has a highly fibrous and dense structure that provides exceptional strength and resilience.

Its distinctive composition allows it to withstand the physical stresses and movements that occur during incubation and prevent the yolk from settling or rotating within the egg.

Additionally, the chalaziferous layer’s protein and riboflavin content are uniquely suited to support the embryo’s growth and development, providing essential nutrients in a highly concentrated form.

Its ability to maintain the egg’s structural integrity and support embryonic development makes the chalaziferous layer a truly remarkable and unique feature of the egg..

Vitelline Membrane

The transparent membrane that encases the egg yolk is essential in maintaining its integrity and preventing mottling. Mottling occurs when the surface of the yolk appears speckled with light blotches or patches, which can be unappealing to consumers.

Therefore, the durability and strength of the vitelline membrane play a crucial role in ensuring the visual appeal and quality of the egg.

Nucleus of Pander

The egg also contains a small white yolk plug, which is purely composed of nutrients and has no developmental significance.

This plug serves as a reserve of food for the developing embryo and plays a minor role in the overall architecture of the egg. Its composition and location are unique to each egg and can be used to identify and classify different types of eggs.

Germinal Disk (Blastoderm)

The blastodisc is a small, round, white patch located on the yolk’s surface, measuring between 2 and 3 mm in diameter. This area serves as the sperm’s entry point and contains the egg’s nucleus.

The embryo develops from the blastodisc and begins to form blood vessels that penetrate the yolk, providing nourishment for its growth.

Yellow Yolk

The egg yolk is a rich source of vitamins, minerals, and nutrients, providing nearly half of the egg’s protein, all of the fat, and cholesterol.

Compared to the egg white, the yolk has a lower water content and higher protein content, as well as most of the egg’s vitamins and minerals, such as iron, vitamin A, vitamin D, phosphorus, calcium, thiamine, and riboflavin.

Lecithin, a potent emulsifier, is also present in the yolk. The color of the yolk can range from a subtle yellow to a magnificent deep orange, depending on the breed and diet of the hen.

White Yolk

The latebra is a fascinating enigma in the world of egg biology. This intriguing feature of the egg yolk appears as a bright white spot at the center of the yolk, due to its lower fat content.

While its function is not yet fully understood, the latebra is thought to play a pivotal role in the formation of the layers that surround it. Its unique appearance has caught the attention of researchers who have studied it using Magnetic Resonance Imaging.

Internal Albumen

Imagine holding an egg in your hand and observing its structure. You would notice a thin, transparent membrane coating the yolk, and inside this membrane, there is a compact, fibrous layer known as the inner thick white.

This layer, composed mainly of albumen, surrounds the yolk and serves to provide it with essential nutrients. The most remarkable feature of this layer is the chalazae, two opposing twisted strands of protein that emerge from the top and bottom of the egg and converge at the yolk’s center.

These chalazae act as a natural suspension system, holding the yolk in place and preventing it from shifting around within the eggshell.

Air Cell

When a hen lays an egg, the temperature of the egg starts to decrease, causing the contents to contract and create an air cell between the inner and outer membranes.

As the egg matures, carbon dioxide and moisture escape through the pores of the shell, and air enters, causing the air cell to expand. This natural process provides an ideal environment for the growing embryo.

Interestingly, the size of the air cell can be used to estimate the egg’s freshness. The larger the air cell, the older the egg, so it’s essential to store eggs properly to maintain their quality and prevent the growth of harmful bacteria.

Cuticle or Bloom

The eggshell is an incredible work of nature, produced by the shell gland of the oviduct in hens. It features a protective coating known as the cuticle or bloom, which plays a crucial role in reducing moisture loss and preventing bacterial penetration by sealing the pores.

Unfortunately, the cleaning process used to prepare table eggs often removes a substantial amount of the cuticle, which can compromise the egg’s integrity and pose potential health risks.

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