The female sex cellis anovum!

It matures in the ovary, as part of the follicle. This is a large, rounded cell that is not capable of active movement. It can only move passively due to the flickering of the cilia and the contraction of the smooth muscle tissue of the female genital tract. It also contains a large volume of cytoplasm compared to sperm.

Outside, the ovum is surrounded by several tunics:

1. OVOLEMMA is a typical cell membrane or plasmolemma. It has the same structure as the membranes of all cells (bilipid layer, proteins, carbohydrates).

2. ZONA PELLUCIDA. In its natural state, this layer is transparent and shiny. But after staining it looks like a red ring around the ovum. This tinica consists of glycoproteins and glycosaminoglycans, which form three fractions - ZP1, ZP2 and ZP3.

ZP3 is N-acetylglucosamine. It is a receptor for the female reproductive cell and ensures the recognition of the sperm of its own kind.

3. CORONA RADIATA - this structure is formed by the processes of follicular cells, which are located outside of the corona radiata. The processes extend from follicular cells and attach to the zonapellucida. This membrane is quite dense and serves as a protection for the ovum and also provides its nutrition, as it transports nutrients to it from the follicular cells.

4. FOLLICULAR CELLS are epithelial cells that lie around the ovum in several layers. Function – trophic function and protection.

Inside the ovum contains a large volume of cytoplasm, a nucleus with a diploid set of chromosomes, EPS, Golgi complex and many ribosomes. Also in the cytoplasm there are two types of granules: yolk and cortical.

Yolk granules contain yolk, which is the nutrient material for the embryo. In humans, the ovum contains small amount of yolk because its reserves in large quantities are not needed due to the hematotrophic type of nutrition, when the embryo receives nutrients from the mother's blood. Such an ovum is called oligolecital. Also, the yolk granules in the female sex cell are evenly distributed - this is an isolecital ovum.

Birds, for example, have a lot of yolk and it is unevenly distributed throughout the cage. In this case, the entire yolk is in one part of the cell - the vegetative pole, and the nucleus and organelles are shifted by the yolk to the opposite part of the cell - the animal pole. The type of ovum needs to be known, since the stages of embryonic development such as cleavage and gastrulation will depend on this.

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