noun, plural: egg cells
In humans, the ovum is the largest cell visible to the naked eye. It is about 0.1 mm in size in humans. It is produced in the ovary and eventually released into the fallopian tube during ovulation. It consists of protoplasm (with some yolk) surrounded by a thin cell wall (vitelline membrane). It may also have a noncellular covering (zona pellucida). Within the cell is a large nucleus (germinal vesicle), with a nucleolus (germinal spot). The cell is haploid so that when a sperm cell fertilizes it, it forms a diploid zygote.
Compare: sperm cell