An element is matter than cannot be separated into different types of matter by ordinary chemical methods.

Heredity is the passing on of physical or mental characteristics genetically from one generation to another. Heredity is made possible via large strings of chromosomes which carry information encoded in genes.

The rows of the Periodic Table are called periods and contain elements that have the same number of electron shells ordered from lower to higher atomic number.

During intercourse, the penis ejaculates sperm, produced in the testes, into the vagina. Some of the sperm makes their way to the uterus where, if they encounter an egg to fertilize, unite with the ovum to form a fertilized egg or zygote. The zygote then may implant in the uterus and eventually develop into a fetus.

Veins carry blood back to the heart from the body. While arteries are thick-walled because they carry oxygenated blood at high pressure, veins are comparatively thin-walled as they carry low-pressure deoxygenated blood. Like the heart, veins contain valves to prevent blood backflow.