Sexual Reproduction in Humans: Creating Life Together

 

What is Sexual Reproduction?

Definition:

• Sexual reproduction in humans is the process where a male gamete (sperm) and a female gamete (egg) fuse during fertilization to produce a zygote. This zygote grows into a baby!

 

Male Reproductive System

 

 

Structure	Function
Testes	Produce sperm (male gametes) and the hormone testosterone.
Scrotum	Protects the testes and keeps them at a lower temperature for sperm production.
Sperm Ducts	Carry sperm from the testes to the urethra.
Prostate Gland	Adds fluid to sperm to create semen, which helps sperm survive and move.
Urethra	Tube that carries semen and urine out of the body (but never at the same time!).
Penis	Delivers sperm into the female reproductive system during intercourse.

 

Female Reproductive System

 

 

Structure	Function
Ovaries	Produce eggs (female gametes) and the hormones estrogen and progesterone.
Oviducts	Also called fallopian tubes, they transport eggs from the ovary to the uterus; fertilization occurs here.
Uterus	A muscular organ where the embryo implants and develops into a fetus.
Cervix	The narrow opening between the uterus and vagina.
Vagina	The birth canal and the entry point for sperm during intercourse.

 

Fertilization: The Magic Moment

Definition:

• Fertilization is the fusion of the nuclei of a sperm and an egg to form a zygote.

 

• Fetilisation occurs in the oviducts
• The sex cells involved have certain adaptations that help increase their chances of fertilisation

Steps of Fertilization:

1. Sperm Journey: Millions of sperm are released into the vagina during ejaculation.
2. Egg Meets Sperm: One sperm reaches the egg in the oviduct.
3. Fusion: The sperm’s nucleus fuses with the egg’s nucleus to form a zygote.

 

Adaptive Features of Gametes

 

 

Feature	Sperm	Egg
Size	Tiny.	Large.
Structure	Has a flagellum (tail) for swimming and an acrosome with enzymes to penetrate the egg.	Contains energy stores and a jelly coat for protection.
Can it move?	Highly mobile, swims to the egg.	Non-mobile, remains in the oviduct.
Numbers	Produced in millions.	One egg is released per cycle.

 

Development of the Baby

1. Zygote to Embryo:
   After fertilization, the zygote divides into a ball of cells called an embryo. $$\text{Zygote} \to \text{Embryo}$$

2. Implantation:
   The embryo attaches to the lining of the uterus.
3. Fetal Development Structures:

 

 

Structure	Function
Placenta	Transfers nutrients, oxygen, and waste between mother and fetus. Filters some harmful substances.
Umbilical Cord	Connects fetus to placenta for exchange of nutrients and waste.
Amniotic Sac	Protects the fetus and contains amniotic fluid.
Amniotic Fluid	Cushions and protects the fetus from shocks.