Question

Acrosomal reaction of the sperm occurs due to
A) It's contact with zona pellucida of the ova
B) Reactions within the uterine environment of the female
C) Reactions between epididymal environment of the male
D) Androgens produced in the uterus

Answer 1

Hint:The Acrosome along with the acrosomal enzymes are the to first come in contact with the zona pellucida of the ovum.

Complete answer:
The head of the sperm cell that contains the Acrosomal enzymes is called the acrosome.
The entire process of the fusion of the male and the female gamete starts at copulation or mating of the male and female counterparts of similar species. When the male delivers it's semen into the genital tract of the female, each drop of the semen contains approximately 1.5 million spermatozoa. Because of the presence of a tail, the spermatozoa are able to swim to the place (fallopian tube) where the ovum is present. Only 3 to 4 sperm cells reach successfully to the ovum, rest are either killed or lose their motility in the way.
Before fertilization, the first portion of the sperm cell that comes in contact with the ovum is the acrosome.
When the acrosome and the zona pellucida (outer layer of ovum) come in contact, the acrosome reaction allows the sperm to release Acrosomal enzymes by exocytosis, so as to penetrate through the zona pellucida. Species specific zona pellucida contain sperm receptors that stimulate a series of enzymatic reactions that further leads to the fusion of the plasma membrane with the Acrosomal membrane.
The hormones secreted by the ovum like progesterone, LPA, LPC triggers the acrosome reaction.
The enzyme content of the acrosome is mainly digestive and perhaps helps in breaking down the membranes of the ovum so as to facilitate the smooth entry of the best swimmer sperm into the egg. Post the Acrosomal reaction, fertilization occurs with the cytoplasm of the two gamete cells uniting to form one cytoplasm with two nuclei. Further division and cell cycle takes place to form the zygote and then the embryo.

Hence the correct answer is option (A.)

Note:After the acrosome reaction, the ovum and the sperm fuses to form the zygote. The zygote undergoes cell division to form a 32 celled blastula which is further divided to form the embryo which gets embedded in the placenta of the uterus.