Sexual reproduction in humans

The male reproductive system includes: Testes (produce sperm and testosterone), Scrotum (holds testes at optimal temperature), Sperm ducts (transport sperm), Prostate gland (secretes fluid for semen), Urethra (carries semen and urine), and Penis (delivers sperm).

The female reproductive system includes: Ovaries (produce egg cells and estrogen/progesterone), Oviducts (transport egg cells to uterus, site of fertilization), Uterus (where the embryo implants and develops), Cervix (lower part of uterus, opens to vagina), and Vagina (receives sperm).

Sperm cells have: a Flagellum (tail) for motility, numerous Mitochondria to provide energy for swimming, and Enzymes in the acrosome to break down the egg's outer layers, allowing penetration for fertilization.

Egg cells contain Energy stores (nutrients) to nourish the developing embryo after fertilization, and a Jelly coat which changes its structure after fertilization to prevent more than one sperm from entering.

Egg cells are significantly larger than sperm cells. The large size of the egg cell is due to its large cytoplasm that contains energy stores for the developing embryo, whereas sperm cells are small and streamlined for motility.

After fertilization, the zygote undergoes rapid cell division to form an embryo, a ball of cells. The embryo implants into the lining of the uterus where it continues to develop.

The umbilical cord connects the fetus to the placenta. It contains blood vessels that transport oxygen, nutrients, and antibodies from the mother's blood to the fetus, and removes carbon dioxide and other waste products from the fetus's blood.

The placenta facilitates the exchange of dissolved nutrients, gases (oxygen and carbon dioxide), and excretory products between the mother's blood and the fetus's blood. It also produces hormones to maintain the pregnancy.

The amniotic sac is a membrane filled with amniotic fluid that surrounds and protects the fetus. The amniotic fluid cushions the fetus against impacts and allows it to move freely, aiding muscle and bone development.

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Sperm cells are motile, meaning they can move independently using their flagella. Egg cells are non-motile; they do not have the ability to move themselves and rely on the oviduct to transport them.