Question

The function of hyaluronidase is
A) To form cone of reception in egg
B) To puncture the vitelline membrane of egg
C) It is not produced in human sperm
D) None of the above

Answer 1

Fertilization in humans have several steps .The first step constitutes an acrosomal reaction in which enzymes released from the acrosome break the vitelline membrane of the egg and after which plasma membrane depolarizes to promote monospermy.

Complete answer: Fusion of male and female gametes is called fertilization .A zygote is formed after fertilization. Secondary oocytes are released from graafian follicle and reach the ampullary isthmus junction. After coitus semen having sperms is inseminated into the vagina. Sperms move through the uterus and reach the ampullary isthmus junction where fertilization occurs.
Steps of fertilization :
Acrosomal reaction: For this reaction optimum temperature, pH, calcium, and magnesium ions are required. Sperm lysins such as hyaluronidase, zonalysin are present in acrosomes and are released which helps in the fusion of the plasma membrane of secondary oocyte and sperm. Contents of sperm enter the oocyte and the plasma membrane depolarizes to prevent polyspermy.
Cortical reaction: Cortical enzymes are released by cortical granules found under the plasma membrane of the oocyte. These enzymes further harden zona pellucida to prevent polyspermy
Sperm entry: At the point of contact between sperm and secondary oocyte a cone of reception is formed which receives the sperm
Karyogamy: Haploid ovum and second polar body are produced after completion of the second meiotic division in the secondary oocyte as the sperm enters the oocyte. Nuclei of sperm detach from the entire sperm and fuse with the female pronuclei and this finally leads to the production of a zygote.
Hence, the correct answer is Option B

Note: Acrosome contains a group of enzymes called sperm lysins for example hyaluronidase. Zonalysin which is released and helps in sperm and oocyte fusion as it punctures the vitelline membrane.