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.

Food is mixed with gastric acid and pepsin in the stomach to help break down protein.

Tough fibrous cords of connective tissue called tendons connect muscles to the skeleton while another type of connective tissue called ligaments connect bones to other bones at joints (elbow, knee, fingers, spinal column).

Vitamins are necessary for a wide variety of bodily processes. Some vitamins like Vitamins A and C come from diet but others, like Vitamin D, are generated in response to sunlight.