How many cells are there in an egg?

Typically, an egg produced by a female organism contains only one cell, which is the reproductive cell or gamete. In animals, including humans, this cell is called the ovum or egg cell, which is produced in the ovary of the female reproductive system.

The ovum is one of the largest cells in the body and can be seen with the naked eye in some species, such as birds. It is surrounded by a protective layer called the zona pellucida, which helps to protect the egg and also plays a role in the fertilization process.

During fertilization, the ovum is fertilized by a sperm cell, which forms a zygote. The zygote then undergoes cell division and differentiation to form the various cells and tissues of the developing organism.

Therefore, while a single egg typically contains only one cell, the resulting organism that develops from the fertilized egg contains billions of cells that make up its various tissues and organs.