Nerve cell is the longest cell,
ovum is the largest cell in human body,
an ostrich's egg is the largest cell in the whole universe.

The largest cell in the human body is the ovum, also known as the egg cell. The ovum is the female reproductive cell and is responsible for fertilization and the development of a new individual. It is significantly larger than other cells in the body and can be seen with the naked eye.

The ovum is a specialized cell that is produced in the ovaries of females during a process called oogenesis. It is surrounded by a protective layer called the zona pellucida and is released from the ovary during ovulation. The ovum then travels through the fallopian tubes where it can be fertilized by a sperm cell.

Here is a detailed explanation of how the ovum is the largest cell in the human body:

1. Size: The ovum is approximately 0.1 millimeters in diameter, making it one of the largest cells in the human body. It is visible to the naked eye, unlike most other cells which require a microscope to be seen.

2. Structure: The ovum is a spherical cell with a large cytoplasmic volume. It contains various organelles such as mitochondria, Golgi apparatus, and endoplasmic reticulum, which are essential for its growth and development.

3. Nucleus: The nucleus of the ovum contains the genetic material, including the chromosomes, which carry the genetic information from both the mother and father. This genetic material is responsible for determining the characteristics of the offspring.

4. Function: The main function of the ovum is to carry the mother's genetic material and be available for fertilization by a sperm cell. Once fertilized, the ovum undergoes a series of divisions and develops into an embryo, which eventually implants in the uterus and develops into a fetus.

5. Lifespan: The ovum has a limited lifespan and can only be fertilized within a specific window of time. After ovulation, it can survive for about 12-24 hours. If fertilization does not occur within this timeframe, the ovum disintegrates and is shed along with the uterine lining during menstruation.

In conclusion, the ovum is the largest cell in the human body due to its size, structure, and function in reproduction. It plays a crucial role in the creation of new life and carries the genetic material necessary for the development of an individual.