Final answer:
The corona radiata is a layer of granulosa cells that surrounds the oocyte, and it must be penetrated by the sperm for fertilization to occur. It is part of the ovarian follicle and is crucial in the fertilization process by ensuring only capacitated sperm achieve penetration.
Step-by-step explanation:
The ring of elongated cells that radiate from the ovum and are held together by hyaluronic acid is known as the corona radiata. This is a layer of granulosa cells that surrounds the oocyte and plays a crucial role during fertilization. The corona radiata must be penetrated by sperm before fertilization can occur. It is an important part of the ovarian follicle, which is the functional unit of the ovary consisting of a nest of epithelial cells surrounding an egg.
Upon ovulation, an oocyte is released from the ovary, and it is accompanied by the corona radiata into the fallopian tubes (oviducts). This protective layer, together with the underlying zona pellucida, a glycoprotein membrane, ensures that only capacitated sperm can penetrate and achieve fertilization, leading to the formation of a diploid zygote.