Question

What is correct about zona pellucida?

• A. It is a cellular layer covering the primary oocyte.
• B. It is a glycoprotein layer around the secondary oocyte.
• C. It is purely a proteinaceous layer around the secondary oocyte.
• D. It is the plasma membrane of secondary oocyte.

Answer 1

The correct option is B It is a glycoprotein layer around the secondary oocyte.

Ovum is released in the secondary oocyte stage from the ovary. It is arrested in the metaphase II of meiosis II at the time of release. Secondary oocyte is spherical in shape and almost without yolk. Cytoplasm is present with a large nucleus. It is surrounded by many layers. It is surrounded first by a plasma membrane-like all animal cells. After the plasma membrane, a transparent layer called zona pellucida is present. It is made of glycoproteins. It is synthesised by oocyte itself. A narrow vitelline space is present between the zona pellucida and plasma membrane. Outside the zona pellucida layer, there are radially arranged follicular cells forming another layer known as corona radiata present.