Fertilization in humans

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Fertilization begins with the fusion of two haploid cells into a diploid cell, the two haploid cells being a sperm cell and an egg cell into the diploid cell being zygote. The union can either be an external fertilization or an internal fertilization. This essay will focus on the internal fertilization found in mammals, and more specific, in humans. The first part will consider human anatomy of both the female and male sexual reproductive systems, and then follows a description of the biological processes which take places after ejaculation and the forming of a zygote.

In humans both females and males are equipped with a system or a structure of organs, called reproductive organs, necessary to perform sexual intercourse or coitus, the event which may lead to a development of an embryo. The male reproductive system consists of two testes, a system of ducts or channels that store and transport sperm to the exterior, the glands that empty into these ducts, and the penis. Spermatogenesis, the process of sperm formation, takes place in the testes. Interstitial cells synthesize and release testosterone. The result of several changes through spermatogenesis is a spermatozoa (sperm). The head of the sperm consists of nucleus, which contain DNA and the tip of the head/nucleus is covered by the acrosome, a protein filled vesicle packed with enzymes necessary in fertilization. Typically, the human male manufactures around 30 million sperm each day. (Windmaier, Raff and Strang, 2011)

References:
  1. Simerly, Calvin, et al. “The paternal inheritance of the centrosome, the cell’s microtubule-organizing center, in humans, and the implications for infertility.” Nature medicine 1.1 (1995): 47-52.¬†https://www.nature.com/nm/journal/v1/n1/abs/nm0195-47.html
  2. Forman, R., et al. “The influence of transient hyperprolactinemia on in vitro fertilization in humans.” The Journal of Clinical Endocrinology & Metabolism 60.3 (1985): 517-522.
  3. Boyers, Stephen P., et al. “The effect of polyploidy on embryo cleavage after in vitro fertilization in humans.” Fertility and sterility 48.4 (1987): 624-627.
  4. Schlesselman, James J. “How does one assess the risk of abnormalities from human in vitro fertilization?.” American journal of obstetrics and gynecology 135.1 (1979): 135-148.
  5. Nayudu, P. L., et al. “Follicular characteristics associated with viable pregnancy after in vitro fertilization in humans.” Gamete research 18.1 (1987): 37-55.

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