When a sperm and egg fuse to form a zygote, the nucleus of the sperm enters the cytoplasm of the egg. As a result, the father's genome is passed onto the offspring, but no cellular organelles from the sperm are transferred. Any DNA contained in the mitochondria must come from the mother's egg, and could not have come from the cytoplasm of the sperm. The offspring will inherit all mitochondrial DNA from the mother.

This allows geneticists to trace mitochondrial lineages to find distant ancestors and track the evolution of species.

Following ovulation, the remaining follicle previously containing the egg is called the corpus luteum. This structure will release progesterone, and continue to do so if the egg is fertilized and a zygote is formed. If no pregnancy occurs, the corpus luteum will degrade into the corpus albicans.

The luteal surge is characterized by a sharp increase in estradiol (estrogen) levels, which then causes an increase in luteinizing hormone levels. This event causes ovulation to take place.

The release of the secondary oocyte from the follicle is called ovulation. During this process, a hole called the “stigma” is formed and it allows the secondary oocyte to leave the follicle surrounded by a layer of cells called the cumulus oophorus. After its release, the secondary oocyte enters the fallopian tube.

Leading up to ovulation, the developing follicle secretes estrogen. Over time, this secretion increases estrogen concentration. This high concentration of estrogen triggers the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary gland. The spike in LH and FSH concentrations lead to the release of the secondary oocyte from the follicle. Progesterone, on the other hand, is only present at low concentrations at the time of ovulation. Progesterone levels rise after ovulation.

The slow increase in estrogen concentration leading up to ovulation triggers the secretion of luteinizing hormone (LH) from the anterior pituitary gland. The spike in LH initiates signal transduction pathways that release proteolytic enzymes. These enzymes create a hole, or stigma, in the follicle that allows the secondary oocyte to exit.

During the follicular phase of the estrous cycle, estrogen, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) are in a positive feedback loop. High concentrations of estrogen stimulate the anterior pituitary gland to secrete LH and FSH.

The increase in luteinizing hormone (LH) concentration during the follicular stage of the estrous cycle leads to the release of proteolytic enzymes from the follicle. These enzymes degrade the follicle tissue and create a hole called the “stigma.” The secondary oocyte exits the follicle from the stigma in a process called ovulation.

Semen is a fluid that contains sperm cells, proteolytic enzymes, lipids, and fructose. The prostate gland, bulbourethral gland, and seminal vesicles all contribute to the makeup of semen. Semen protects and transports sperm cells inside the female reproductive tract as they seek out the egg cell.

Semen is the fluid that contains and transports sperm cells to the female reproductive tract. The female vagina is acidic due to lactic acid output from normally occurring bacteria in the vagina. In order to protect sperm cells from the acidic environment, semen is alkaline.