NEETZoologyHuman Reproduction
During fertilization in humans, a sperm must traverse several layers to reach the cytoplasm of the ovum. Arrange the following structures in the correct sequence from the outermost to the innermost layer encountered by the sperm: (I) Zona pellucida (II) Plasma membrane (III) Corona radiata (IV) Perivitelline space
Options
- A(I) (III) (IV) (II)
- B(III) (IV) (I) (II)
- C(III) (I) (II) (IV)
- D(III) (I) (IV) (II)
Correct answer
D. (III) (I) (IV) (II)
Step-by-step solution
When a sperm approaches the ovum during fertilization, it first encounters the outermost cellular layer, which is the corona radiata (III). With the help of acrosomal secretions, it penetrates this layer and reaches the acellular glycoprotein layer, the zona pellucida (I). After crossing the zona pellucida, the sperm enters the perivitelline space (IV), which is the narrow gap separating the zona pellucida from the ovum. Finally, the sperm reaches and fuses with the plasma membrane (II) of the ovum, allowing its en