Question

Why is the human ovum called alecithal?

Answer 1

The cell which is released from the female reproductive organs and is capable of developing a new organism when fertilized or united with a sperm cell is known as an ovum.

Complete answer:
The human ovum is alecithal as it consists of the negligible amount of yolk in it as the embryo develops into the egg and remains connected to the mother by obtaining nutrition from the mother through the placenta and hence requires a negligible amount of yolk in it. Ovum is a single cell which gets released from the reproductive organs of the female that are known as ovaries. They get united with the sperm cell to get developed into a new organism after the process of fertilization and the outer surface is covered by a layer of cells which are immature egg cells at the time of birth.
The process of formation of ova is known as oogenesis in which the female gamete is produced and is transported through the fallopian tube where it gets fertilized by the sperm cells. Oogenesis is initiated in the embryonic stage and is the first part in mammals which starts in the germinal epithelium and gives rise to the development of ovarian follicles which are the functional unit of the ovary. It constitutes several sub-processes such as cytogenesis, ootidogenesis, and the maturation to form an ovum.

Note:
The biggest cell of the body is the egg cell which is around a hundred microns in diameter similar to the strand of a hair. The type of eggs are classified on the basis of the amount of yolk present. According to it there are four types:
Alecithal : The amount of yolk is almost absent as present in mammals.
Microlecithal: Very little amount of yolk.
Mesolecithal: The amount of yolk is moderate as in Amphibians, Annelids etc.
Megalecithal: They consist of a large amount of yolk. This is found in reptiles, insects etc