The Human Egg Cell.
The human egg cell is also known as the ovum. With a spherical structure it is the largest cell in the human body measuring about 0.2mm in diameter. The function of the ovum is to reproduce, when fertilized by the sperm cell the ovum is capable of creating a new living organism. The size and shape of the ovum gives it space to store and create nutrients (see fig 3) (Boyle and Senior 2008) The ovum is bounded by the egg follicles of the ovaries and is produced by primitive germ cells which are located in the substance of the ovaries, this process is called oogenesis. Once a month during ovulation the ovum are released due to an opening of a follicle at the surface of the ovary. The ovum is then carried by the uterine tube into the uterus. If the egg has not been fertilized it is released from the uterus during menstruation. The ultra-structure of the ovum consists of; the nucleus, nucleolus, cytoplasm, zona pellucida and the corona radiata(see fig.3.) The nucleus known as the germinal vesicle is central to the ovum and Consists of most of the genetic material (DNA). The nucleus contains a nucleolus known as the germinal spot and they are both enclosed by a nuclear membrane. The cytoplasm of the ovum is made up of fat and protein like substances enabling the cell to store and create nutrients to nourish the embryo in the early stages of development. The zona pellucida is a thick outer membrane providing protection but can be easily penetrated by the sperm cell. The corona radiata, attached to the zona pellucida, is made up of two to three layers of cells produced from the follicle. The main function of the corona radiata is to supply the ovum with protein. (Human Anatomy)
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