The testes are male reproductive organs that produce and store , which is the male gamete containing half of the DNA in somatic cells. The typically 28-day process of egg release from the ovaries and, if fertilization does not occur, release from the body, is known as the cycle. If two eggs are released and fertilized by two different sperm, then twins will occur. If a hormone operates by entering a cell's nucleus and altering the expression of its DNA, then it is classified as a/n hormone. Once sperm cells are mixed with seminal fluid to provide protection and nutrition, this mixture is known as . The bulbourethral and glands play an important role in providing additional fluids to semen production. The first phases of a new zygote's growth through mitosis occur in the . The germ layer will eventually develop into the skin and nervous system. A fetus growing in the uterus does not eat food or drink water. Instead, important nutrients, antibodies, and molecules pass from the mother through the . Make a list, or write a short paragraph, that explains the major stages of pregnancy after fertilization, through childbirth. Provide as much detail as possible.