A textbook for second-grade students in primary schools that includes diagrams of reproductive organs and discussions about sexual abuse has sparked controversy, with the publisher explaining that it is simply serving the purpose for which it was written.

A mother from Hangzhou, East China's Zhejiang Province, said on Sina Weibo that she was shocked to find that her child's textbook includes pictures of male and female reproductive organs.

She posted a picture of a chapter that teaches children how to protect themselves from sexual abuse. The picture shows a woman asking to see a boy's genitals. The woman claimed the picture was too much for her to handle, let alone her child.

Her post sparked heated discussions online, with many agreeing that this textbook is "too much" for second graders, normally aged from 7 to 9.

Beijing Normal University Publishing Group told the China News Service that given its sensitive topic, the book  was examined especially carefully and the content is in accordance with their intentions.

The group issued a series of textbooks named Zhen'ai Shengming, or "Cherish Life," which are used with students from grades one to five in primary school. Apart from teaching children how to protect themselves, the series also introduces sexual intercourse, the physical changes of puberty and tells children that homosexuality is normal.

Tong Xiaojun, a professor at the China Youth University for Political Sciences, said that children are curious about where they come from, but if their questions are not answered in a proper way they may seek answers from pornographic books or websites, which may mislead them.

Tong added that children should be informed about sex education as they get older.

"What matters is what kind of information they should be told about at different ages," Tong said.

Using these kinds of textbook is tricky, Zhang Meimei, a professor of sexual education at Capital Normal University, told CNS, adding that schools should discuss such courses with parents first and gain their support, because parents are also responsible for teaching their children.

An unnamed father of a second-grade student told the China News Service that though this kind of course is good, he still felt embarrassed when his son showed him the book.