Introduction to Human Reproduction | Biology for Grade 12 PDF Download

What is Reproduction? 

Reproduction is the process of giving birth to their young ones which are identical to their parents. As we all are aware of, the process of reproduction in humans is sexual reproduction, which involves internal fertilization by sexual intercourse.

How do Humans Reproduce? 

Human reproduction is any form of sexual reproduction resulting in human fertilization. It typically involves sexual intercourse between a man and a woman. During sexual intercourse, the interaction between the male and female reproductive systems results in fertilization of the woman's ovum by the man's sperm.

Humans reproduce sexually. They are viviparous, i.e. giving birth to the young ones. The process of reproduction in humans comprises a number of sequential steps: 

1. Gametogenesis- production of male (sperm) and female (ovum) gametes
2. Insemination- transfer of male gamete to female genital tract
3. Fertilization- the fusion of gametes to form a zygote
4. Blastocyst development- the continuous mitotic division in zygote
5. Implantation- attachment of blastocyst to the endometrium of the uterine wall
6. Gestation- embryonic development (9 months in human)
7. Parturition- childbirth

Embryology is the branch of biology which deals with the study of all those processes, which take place during the development of the fetus. 

Sexual Dimorphism in Human Beings

When male and female individuals are differentiated externally, the phenomenon is called sexual dimorphism. Human beings show sexual dimorphism. The characters which distinguish the males and females externally are known as secondary sex characters.

Primary sex organ :

• Essential organs form the gametes. 
• In males, the gamete-forming organs are the testes. 
• In females, the corresponding organs are ovaries. 
• The male gamete is a spermatozoon. 
• The female gamete is the ovum.

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Secondary sex organ :

• These organs form the passage for the gametes to help the union of male & female gametes.
• In males, these include the epididymis, vas deferens, seminal vesicles, prostate, bulbourethral glands & penis etc. 
• In females, these organs are the fallopian tube, uterus and vagina, Bartholin gland etc.

Development of Sex organs:

• During intrauterine life (IUL) testis & ovary develop from the mesoderm. 
• They develop in the abdominal cavity. 
• At the time of birth, testes descend down into the scrotal sac but ovaries remain in the abdominal cavity.