An ovum refers to the female egg cell in mammals including humans. The sperm, meanwhile, is its male counterpart when talking about reproductive cells. In the case of humans, for example, one egg cell and one sperm cell is what it takes for the ovum or egg cell to be fertilized and go through a long process of development until this particular unity of cells becomes a baby. When viewed microscopically, it is quite obvious to see the ovum to be bigger than the sperm cell. In fact, millions of sperm cells may actually surround a single ovum, but only one of them will be able to fertilize it. The basic reason for a bigger ovum is because of its contents. The ovum contains various nutrients that may be necessary when it becomes fertilized by a sperm cell. Without a food source, the ovum will not be able to survive for possible embryonic development.
When an ovum or egg cell, for example, is released from the female’s ovaries from either side of the pelvis, it will travel a long course from the fallopian tubes to the uterus. Under normal circumstances, the ovum will be able to retain its nutrient content for one to three days as it travels towards the uterus. During this period, sperm cells may be able to meet the single ovum for possible fertilization. When conception happens, the fertilization will then trigger the start of embryonic or baby development. In order for embryonic development to push through and be successful, the ovum must be able to retain its food source and must be fertilized within one to three days. This why the ovum, or female egg cell, is literally bigger in size because it contains these various nutrients. In a sense, the ovum is always preparing itself and always ready for possible fertilization and embryonic development.